We just went though a long discussion and quite a bit of research about improving on the fast corrosion and breakage risk of the zinc plated header bolts on the GS500. The result seemed to be that either stainless steel bolts, or stainless studs fixed in place with grade 272 Loctite, were a step forward. Loctite did not recommend any of their threadlockers for this application, but confirmed that a lot of people use it for header studs and it generally seems to do OK despite the heat probably being well over spec on the side of the bolt closest to the pipe. Professional engineering articles on exhaust system materials leaned strongly to stainless and did not even mention zinc (see http://dergipark.gov.tr/download/article-file/318350) A lot of modification shops are also using stainless hardware. So, we could feel good about that shiny stainless steel hardware that was much less prone to corrosion, and conclude that Suzuki was using zinc plated steel as a cost reducing measure when they should have paid a little more for stainless.
OK, continuing to read up on this, it is turning out that Suzuki probably deliberately selected zinc plating to prevent corrosion of the aluminum threads in the cylinder wall. Yes, the bolt corrodes badly when exposed to salty water and heat, but it is deliberate "sacrificial" corrosion of the zinc in order to PREVENT galvanic corrosion of the aluminum threads. If the bolt is not replaced quickly enough, then the steel under the zinc starts rusting and the bolt can break during removal. That seemed to be a design problem that we wanted to fix.
As a quick technical summary of why the physics actually favors zinc plating, aluminum has galvanic potential of -0.9. Zinc is -1.25, so with aluminum it becomes the "anode" or "less noble" side that turns to ions and corrodes away. Stainless steel is about -0.5, so it "more noble" than aluminum and it is the aluminum that corrodes (the more negative always corrodes). So, Suzuki's strategy here is that the bike owner should be inspecting those head bolts pretty regularly and replacing them. They're disposable, the aluminum cylinder is not. They should explain that in the service manual, but my Clymer does not. Some guys in Tokyo know, but they're not explaining their deliberate use of the zinc bolt as a sacrificial anode. They probably figured we would have retired our GS500's and moved on to bigger bikes by now, so why waste time explaining every little thing we want to know to keep these low cost bikes in service for decades.
Stainless steel studs that are well sealed with Loctite to keep out water and in dryer environments may only be causing mild aluminum corrosion, but it's there. It might be a few years in a wet environment or 40 years in a dry environment, but eventually the aluminum threads get corroded away while the stainless still looks good. This probably happens faster with stainless bolts that are not sealed or that just have anti-seize.
If you want further technical details, see https://en.wikipedia.org/wiki/Galvanic_corrosion and the corrosion engineer discussions of stainless bolts in aluminum at https://www.finishing.com/271/67.shtml.
My new stainless studs are going on the shelf, and I'm laying in a supply of zinc plated bolts for regular replacement. It's a hassle, but that seems to be the way Mother Nature wants it.
With the greatest of respect...........I think you worry too much :dunno_black:
Maybe so, Sledge, but I did owe it to the members to tell them that the zinc plated bolts were almost certainly deliberate and actually smart. Too bad--I was looking forward to my new SS studs to sort of "Harley-up" this bike.
I fitted stainless studs and nuts without threadlock 18 years ago. Nothing has become loose or corroded and the last time I checked the nuts are still free to turn, dunno about the studs but if they have seized.........so what! They don't need to come out and that's the whole point of them.
Your bike, your choice, do what makes you feel warm and fuzzy :thumb:
I usually Bitccth a lot about the quality of the screw on GS... I am not talking about the finishing on them.. But they are very soft.. especially the Philips bolts.
I saw many of them breaking and seizing in my " bare hands" many times... as soon I have the opportunity I always put some allens (stainless steel or regular steel).
I prefer to get my chances with a good screw bolt in an perhaps oxidized screw hole.. then a crappy bolt in a "theoretically" sound ( saw a bunch of OEM screws pretty rusty) screw hole.
Maybe I will change my mind in the future.... but not for now.
I liked your post... very interesting. But I will keep substituting mines.. too.
Applaud.
:cheers:
Sledge, at least what seems to be the full story of aluminum, zinc, stainless, and threadlocker is out on the table for the members to consider when deciding what to do.
It's great your studs are doing fine after 18 years. If they are corroded in place as you mention to be possible, it's not a problem since they are studs and the exposed threads are not corroding. So, I could certainly see that being a nice permanent solution, especially if the threads are effectively sealed by corrosion or threadlocker, and salt water cannot penetrate and cause so much further corrosion of the threads that they come loose. If I were to change my mind and put these new stainless studs on, I'd probably use a LOT of the 650 degF Loctite 2620 and really seal those guys up. Even with the dissimilar metals and the aluminum being the anode, if the electrolytes (water, salt, and combustion products) cannot get between the metals, there will be little or no corrosion.
But for someone else using stainless steel BOLTS, if they are in a wet salty environment and their aluminum threads are corroding away, then the time comes when they won't hold a new bolt.
I don't really have anything to add but wanted to say how much I've enjoyed reading this thread and the one that began the debate. I plan on doing a bunch of non-scheduled maintenance over the coming winter on my '93 and exhaust studs are on the list. I think I'd rather replace zinc studs now and then than deal with corroded/eroded threads in the head.
Thanks MaxD for the detailed information here. Keep it up! :cheers:
One thing I'll point out to the naysayers: usually the complaint is that the Suzuki/stock bolts are weak. This is an observation usually due to them breaking or being subjectively easily damaged during a repair or maintenance. There are few complaints about the factory bolts failing while in use. To me this says they are not weak or too weak for the intended purpose.
It seems to me that corrosion is likely to happen in a couple of places that impact one's perception that the bolt is weak. First is the threads, either corrosion on the bolt or the threads, second is corrosion usually beneath the zinc forming rust between the portion of the bolt/screw that's engaged in the thread (chassis, engine block, a nut, etc.) and the head of the bolt, and thirdly is the head itself. If neglected, then corrosion in the threads where they are engaged will increase the amount of torque required to loosen or remove the bolt. It will also increase the amount of torque required to achieve correct clamping due to increased friction at the thread interface. Rust in the bolt's shank beneath the head weakens the metal there directly making it less resistant to torque. So if you have a bolt with 1mm of rusted shank beneath the head AND corrosion on the threads as installed into the block/head/etc. then it stands to reason that when you begin to remove the bolt or screw one of two things is likely: either the bolt will break in the rusted area beneath the head (happened to me a dozen times), or, particularly on a Phillips-head (or JIS) screw, the head will strip due to excessive torque required to loosen it. In both cases the typical GSTwin forum member will conclude the bolt or screw is "weak" and insist that it's because the bike was "cheap" and Suzuki are just being cheap. The reality is that the bolt or screw was doing its job just fine until you tried to remove it; more regular maintenance might have been in order, like earlier in the lifetime of the bike, remove and inspect bolts and screws and replace when there is any corrosion.
Of course then the shadetree mechanic know-it-alls will replace these corroded screws with stainless screws, and then in another decade when someone goes to remove those they may find that upon reinstallation the hole where the screw goes, into the head or the block etc., has the threads stripped easily. In this case it's because the corrosion has been moved to the aluminum part as you pointed out due to use of a stainless screw. Then said know-it-all will further conclude this is because Suzuki used "cheese" or some other non-quality material for their cast parts. Certainly not because the person doing the modification was misinformed about the side effects.
I agree that Suzuki probably should tell the owners that removing and inspecting zinc-plated steel bolts and screws that are installed into aluminum parts should be a part of regular maintenance if this risk of corrosion is really very high, and maybe the do in the factory manual, IDK. Maybe this is one of the many things that separates the pros from weekend warriors like myself. Or maybe really Suzuki cared mostly about selling the new functional motorcycles and isn't being negatively affected by these kinds of maintenance issues on decade-plus old motorcycles.
GS500s seem to be generally (anecdotally) regarded as pretty bullet-proof and reliable by users and home-mechanics. Maybe this degradation of hardware is just normal wear and tear and there's really no reason to suspect that these bikes are any different than any others. I seriously doubt Suzuki used different hardware material on a GS500 than they did on a Katana or a Bandit or a GSX-R or a Boulevard. It would just make no sense from a supply-chain standpoint. We're not talking about Tesla here, or a company cutting their teeth on manufacturing of big mechanical items. Suzuki has been at this for a long, long time.
Mr72, I've think you've nailed it with describing the physics and human chain of dominoes here and how they can fall leading to the header bolts breaking. It's a good engineering failure analysis, and reminds me of what the Nobel winning physicist Richard Feynman had to say in his analysis of the O-ring failure that destroyed the space shuttle Challenger. It's the human tendency to deny physics and statistics that is often the greatest cause of failure. BTW, I see from your blog that you are in Austin, a great city. I went to the EE school there at UT, and am in Dallas now.
On this particular issue, the success Sledge reports still has me considering using the stainless studs and really sealing them up. The Suzuki guys knew what they were doing with the zinc plated bolts, but they did not have the newer higher temp threadlockers available to them at the time they did this design. Nor did they fully appreciate that they actually did such a fine job in defining and designing this machine that it was going to be so well loved that a lot of guys were going to get into trying to keep them going till Earth runs out of crude oil. The bike seems to represent the peak of mid-sized parallel twin carbureted motorcyles. I might like to have a new Honda water cooled fuel injected CB500X with 16k mile valve adjustment interval, but I just can't justify it when my GS500 is almost like new, actually does everything I need, and only cost me $70 per year to insure.
Quote from: MaxD on August 23, 2018, 10:03:08 AM
Mr72, I've think you've nailed it with describing the physics and human chain of dominoes here and how they can fall leading to the header bolts breaking. ...It's the human tendency to deny physics and statistics that is often the greatest cause of failure.
Yes, I agree with this, however I will point out the counterpoint with an example. I once owned, at the same time, a BMW 530i (70s) and a Datsun 240Z. It so happened that both cars alternators failed at the same time. I changed the alternator in the Z in literally 15 minutes, and the remanufactured part cost about $30. The BMW, on the other hand, took me several days to get properly replaced due to extremely poor design, and a used (and as it turned out, bad) part cost over $100. Both cars had about the same mileage and the BMW was 6 years newer car, and a far more expensive vehicle to begin with. But the Z was designed to be easily maintained while apparently maintenance was an afterthought for the BMW.
So if such maintenance of bolts etc. is required in a GS500 to prevent damage then I believe it's incumbent on Suzuki etc. to instruct users to perform this maintenance routinely just as they do with valve clearances and engine oil. They had to know there was a risk of corrosion that would make repairs (not maintenance) difficult or costly.
I haven't investigated it but I'd have to truly guess that Suzuki probably does instruct (in the FSM) the inspection of bolts on some kind of interval, but it seems like excessive maintenance to those who don't know the cause (like me) and it's often skipped. Heck, my 2015 Jeep sits out there in my driveway anywhere from 2K to 26K overdue for various "inspect" and "replace if needed" maintenance because my experience from owning other cars is that those things should not be at risk of failing this soon... I mean, really, I should "inspect" the exhaust system and belts and hoses in the cooling system on a brand new vehicle with 6K miles? Well my guess is when I finally get around to it I'll find a bunch of degraded and corroded stuff making life a lot harder on me... like I will likely have to cut exhaust bolts that I could have replaced at 12K miles when they started to corrode (and every 12K thereafter) if I maintained it like a race car.
Jeez!
This is a cheap low quality mass produced motorcycle designed for a limited lifespan, not the space shuttle or a nuclear submarine!
If you are all going to get your panties bunched
about a few bolts that in all likelihood will only ever be undone once or twice in the bikes lifetime heaven help you when something far more significant decides to become stuck or shear off.
Mr72, we'd all like to see better design for maintainability in a machine we like, so it is a small kick in the rear that Suzuki did not spend just a little more on the materials in the bike, and provide better maintenance information. When companies do that, it sometimes really works out great. The first fighter plane deliberately designed for maintainability was the Northrop F-5. Designed in the late 1950's, it is so easy and cheap to maintain that it is still widely used today. This is the plane they were calling a "MiG-28" in "Topgun", and it still holds its own against modern fighters. A real classic whose chief designer was also the lead engineer for the P-51 Mustang that won the WWII air war over Europe, which shows the influence one engineer can have.
I've got an old jeep Wrangler also, and like the GS500 it is an enthusiast vehicle. Even if there are a few places the design and materials are lacking, the nice thing about them is that the interest in keeping them going leads to aftermarket parts and great sources of maintenance information, like this forum. Forewarned is forearmed, which is what we are getting the benefit of here.
Sledge, 72 and I are engineers, so it has been whipped into us to try to get to the bottom of things. Sorry if it seems overly detailed.
Don't remind sledge that I'm a(n) [former] engineer. Please.
Quote from: Kito on August 23, 2018, 04:27:00 AM
I usually Bitccth a lot about the quality of the screw on GS... I am not talking about the finishing on them.. But they are very soft.. especially the Philips bolts...
There are no Phillips screws on your bike. If you're using a Phillips screwdriver, it's very likely that the heads will strip.
Anyone else remember Dennis?
He thought he was an Engineer too!
http://gstwins.com/gsboard/index.php?topic=68354.0
:D :D :D
I have been trying to recall past issues I have had relating to stuck/seized fasteners with the GS5s I have worked on over the years. In addition to the header bolts
The list runs to......
Front mudguard fixings
Fork brace fixings
Front disc mounting bolts
Suspension linkage bolts
Fork caps
Form clamp bolts
Chain guard fixings
Fuel cap bolts
Front brake reservoir lid screws
Engine mounting bolts
Banjo bolts going into the brake callers (front and rear)
Air box mounting screws (inserts spinning in the plastic)
Mirror mounts.
Carb inlet boots.
All of which became stuck to the extent that they could not be removed in the way they were intended to be.
I sincerely hope you will not loose too much sleep worrying about yours :thumb:
Quote from: RichDesmond on August 23, 2018, 05:48:05 PM
There are no Phillips screws on your bike.
???
I think maybe we got lost in translation...
I already had problems with screws on the carbs covers, on the ignition sensors fixtures, at the cam chain tensioner cover, front brake fluid reservoir.. well the list can probably go bigger with more brain effort.. ( I bought my gs about 14 months and I already experience bad things with screws..).
Not all got completely destroyed.. but as soon I realize that the screw fitting is not sound and perfect .. I try to change it.
Quote from: Kito on August 24, 2018, 04:48:23 AM
Quote from: RichDesmond on August 23, 2018, 05:48:05 PM
There are no Phillips screws on your bike.
???
I think maybe we got lost in translation...
I already had problems with screws on the carbs covers, on the ignition sensors fixtures, at the cam chain tensioner cover, front brake fluid reservoir.. well the list can probably go bigger with more brain effort.. ( I bought my gs about 14 months and I already experience bad things with screws..).
Not all got completely destroyed.. but as soon I realize that the screw fitting is not sound and perfect .. I try to change it.
Rich is right, there aren't any Phillips screws on these bikes from the factory. Suzuki uses JIS screws, not phillips. If you try to remove a JIS screw with a phillips screwdriver, you will almost certainly strip the head.
Quote from: sledge on August 24, 2018, 03:06:06 AM
Anyone else remember Dennis?
He thought he was an Engineer too!
http://gstwins.com/gsboard/index.php?topic=68354.0
:D :D :D
I really hope that one of these days you learn that being right isn't an excuse for being an @$$hole. You have a useful wealth of knowledge and experience that we all could learn from if you would just share it politely. However, instead of doing that, you always seem to insult people and seek to destroy everyone else's credibility. Dennis might have been wrong about honing cylinder walls, but he was right about you when he said you're arrogant, nasty, and mean.
SUMMARY: We got into this discussion to understand what was the best way to deal with the corroding header bolt problem. The whole issue of steel bolts in aluminum threads is filled with misinformation and lack of understanding (just try a web search), even among many professional maintainers. It runs the gamut from many maintainers saying "Just do it!" to discussions of how the new U.S. Navy ship USS Liberty has been nearly ruined by it.
Turns out our bolt corrosion was not really a "problem", but a form of solution that just was not explained by Suzuki. Their zinc plated bolts corrode as deliberate sacrificial anodes to save the aluminum threads, and are intended to be replaced when the zinc is mostly corroded off them.
To get around that regular maintenance, and just ugly corroded bolts on our bikes, Sledge has had what seems to be good long term results (18 years) with stainless steel studs in his particular riding environment (salty water exposure not known). The aluminum threads may be corroded inside (they are galvanically sacrificial to stainless), but so far they have held. It is likely that the highest temp version of Loctite available (650 deg F) can seal them fairly decently so that corrosion is limited. We have measured the temp on the outside of the bolt carrier farthest from the pipe at a little over 400 deg F, though it may exceed 650 on the side of the bolt closest to the pipe. But, exceeding the temp spec by a moderate amount does not immediately destroy the Loctite as a sealant--it just renders it weak in grip force. The makers of Loctite have not measured the "burn temp" of the Loctite to say for sure when the Loctite is destroyed and will no longer even function as a sealant. So, using stainless studs with 650F Loctite is likely, but not guaranteed, to be a sound long term solution. If the hottest any part of the seal gets is not more than 750 deg F, then the seal almost surely holds.
There are a few things left we could do to get better understanding:
1. Measure the temp on the inside of the bolt closest to the pipe (my electronic temp probe won't handle it).
2. Consider aluminum bolts or studs to match to aluminum threads. Aluminum bolts and screws are made, but they are much less available. There is a company in the United States, Aluminum Fastener Supply, that specializes in this. They claim the reason aluminum is not more used is not the strength of the bolts, but just an historical mistake that has not yet been fully corrected. They say their business is rapidly growing, being strongly driven by the use of aluminum engines in cars and more use of aluminum fasteners on those American cars. Unfortunately, they don't make metric products.
Sledge, the discussion is not a shot at you. It's just physics, buddy. But, if you want to see just how fast and bad the stainless to aluminum corrosion can be, look up the "lasagna cell". Lasanga (or any salty tomato based food) in a stainless steel pan with aluminum foil on top will corrode holes into the aluminum foil overnight. This is shown with pictures at https://amazingribs.com/more-technique-and-science/more-cooking-science/beware-lasagna-cell-how-some-metals-can-ruin-your
Quote from: qcbaker on August 24, 2018, 05:44:34 AM
Rich is right, there aren't any Phillips screws on these bikes from the factory. Suzuki uses JIS screws, not phillips. If you try to remove a JIS screw with a phillips screwdriver, you will almost certainly strip the head.
Come on...
I though there was just philips and PZs slots... JIS.... JEsus.. F#$$% Christ.
Either way I hate this kind of drivers.... really.. and now.. more then ever.
You got me good Rich.. thanks for teaching me this one!
(https://www.viczcar.com/forum/uploads/monthly_05_2016/post-101663-0-80129900-1462160512.jpg)
Well, it is not a guarantee that you will ruin a JIS screw head by attempting to use a Phillips screwdriver on it. I have done it hundreds of times on my own GS without any problems at all. Using too-small Phillips screwdriver or a badly worn bit will likely screw up the heads. Trying to remove it at a weird angle where you can't get enough force downward into the screw head will also improve the likelihood that you screw it up. But it's certainly not assured that you will screw them up.
However, if the screw is stuck due to corrosion, and if it's weakened because of rust, then no matter what type of screwdriver you use, you will likely damage the head.
FWIW I have never damaged a JIS screw with Phillips screwdrivers on my own 26 year old GS500. But I have snapped off numerous 8mm-head case screws, rounded the inside of an allen-head bolt holding the heel protector on, and in many cases I've elected to replace JIS screws with allen screws when I have to work on that part. I kind of have the sense that this JIS screw thing is a lot more Cliff-Clavening by GS500 owners. Look how smart everybody will think I am when I can point out some trivial thing they are all wrong about!! nyah-nyah!
It may have been a placebo-effect, but I felt that my JIS driver is what helped remove a lot of my carb's screws (but still not all), in comparison to the good quality Phillips driver that seemed to cam out at any opportunity. Maybe not so coincidentally, JIS is mostly mentioned alongside carb topics online (in my research), so it seems that's where the issues are most prevalent.
I much prefer hex key drives to JIS/Phillips/Pozidriv too, but even they're still easy to round out in mildly corroded fasteners. I rounded a allen head footguard bolt the other day too mr72, but luckily managed to cut a slot in it and use a slot drive. Hence my preference for stainless, because as with Kito, I'd rather have a solid head in a potentially corroded thread, than a corroded head and thread. (Stainless Torx drives would still be my ideal! :cool: )
MaxD, I've also considered aluminium fasteners before but just shrugged it off. I suppose they're usually ignored due to their insufficient strength in many circumstances, but the GSs low recommended torque of 9-12 Nm for these headers should be fine unless I'm missing something glaringly obvious? Aluminium and its alloys all obviously have lower Young's moduli and yield strengths than the steels we use, but they must be capable of a measly 9 Nm? I suppose you'd just have to be extra careful not to over tighten them as you'd already be borderline (maybe a lack of redundancy is the issue and reason for not being used? or fatigue?)
Edit:
Pro-Bolt, a UK aftermarket fastener company, sells M8 size aluminium bolts and suggests maximum torque values of 8 to 12 Nm (https://www.pro-bolt.com/torque-information/). Although unsurprisingly they suggest to "not use aluminium bolts in any stress areas e.g. Brake Caliper Fixings, Suspension Mounts, Footrest Hangers, Grab Rails etc."
Max, I tried a search on why aluminum screws and bolts are not more common, and I did not get any authoritative results. The lady I talked to at Aluminum Fastener Supply was the wife of the founder, and though she was knowledgeable, she was not very technical. She has a tech guy, but he was out this week. She did point me to a larger company, Bossard (HQ Switzerland), that I left a tech support request with. I'm guessing it is not JUST history and standard practice that are holding back aluminum fasteners. The head is pretty soft and easy to strip, and there may be corrosion effects as theorized below.
Aluminum has a very slow oxidation process. Bare aluminum develops a coat of aluminum oxide a few nm thick in a few months, which is an electrical insulator. When this coating is developed on purpose, it is called anodized aluminum. Whether nature does it or a deliberate process, once it is on there it inhibits further corrosion, which is why aluminum can last many decades (if not galvanically mismatched) even when exposed to weather. I had an unpainted aluminum 1946 Cessna 140 light aircraft that was over 60 years old and had no corrosion.
My guess is that the main reason aluminum threads do not almost instantly corrode away with stainless bolts is that they are often coated with aluminum oxide when the bolt goes in. It's fairly tough stuff, and if the bolt does not scrape it off, then there is probably some protection provided by that (since it is an electrical insulator, it should inhibit the galvanic process). However, if a new, not yet oxidized aluminum bolt or screw is set into new aluminum threads, then the oxidation process MIGHT fix them together pretty firmly. Trying to remove the bolt/screw may then round off the bolt head or screw slot, since the aluminum is pretty soft compared to steel. Similarly, if an aluminum bolt/screw is set into steel threads, then the aluminum becomes galvanically sacrificial and is weakened, and might be pretty easy to break off.
I don't really know, but my guess is that some combination of these potential problems has prevented aluminum bolts and screws from becoming more popular. I'm an electronics engineer, and don't belong to any mechanical or material engineering professional organizations that might have professional articles on the subject. If we have any mechanical engineers here on the forum, perhaps we could get them to explain it, or use their professional membership article access to get to the bottom of it.
Take a Phillips screwdriver, one closest to the JIS screw you wish to undo. Grind/file about 0.050" off the point. Ok it doesn't make it a JIS screwdriver but it will fit the JIS head a lot better and reduce the chance of camming out and rounding off the head.
Ask any half decent Engineer :thumb:
I do see where you are coming from...
Quote from: qcbaker on August 24, 2018, 06:02:13 AM
Quote from: sledge on August 24, 2018, 03:06:06 AM
Anyone else remember Dennis?
He thought he was an Engineer too!
http://gstwins.com/gsboard/index.php?topic=68354.0
:D :D :D
I really hope that one of these days you learn that being right isn't an excuse for being an @$$hole. You have a useful wealth of knowledge and experience that we all could learn from if you would just share it politely. However, instead of doing that, you always seem to insult people and seek to destroy everyone else's credibility. Dennis might have been wrong about honing cylinder walls, but he was right about you when he said you're arrogant, nasty, and mean.
Arrogant, nasty and mean?
Nahhhh......You have got me wrong. I am just allergic to bullshitters :thumb:
Quote from: sledge on August 24, 2018, 12:34:32 PM
Ask any half decent Engineer :thumb:
Naaaa, we got engineers these days who don't know how to hold a wrench (spanner - translated just for you sledge)
We need to ask an engineer with some grey in their hair ...
And yes shaving the point a bit helps - not just with the JIS crap but also most screwdrivers start necking at the point and a tiny bit up from there.
Cool.
Buddha.
Checking Amazon for useful books on corrosion and material selection, I find that the professional books run $100 to $200 each. It's quite a complicated subject, and the professional books get quite detailed on the theory (many are graduate level engineering text books). There is quite a selection since corrosion is such a problem, costing about 4% of GNP and about $1000 per person per year. Checking inside them as far as Amazon lets you does not seem to turn up the information we need on selecting best fastener materials and methods in easy user guide form.
This downloadable free book seems to do about as well:
http://dl.iran-mavad.com/pdf95/Corrosion%20Control(Casti%20Guide)_iran-mavad.com.pdf
The author seems a solid pro (BS, MS, PhD) with over 30 year of experience in corrosion control. There is one short but applicable chapter for us, which is Chapter 17 "Designing to Control Corrosion". He does not get into a lot of detailed guidance here, perhaps because he makes his living providing additional detail and does not give it away for free. But, the basic strategy of practical corrosion control from the product designer and user point of view is described as:
1. Control the Environment (chemical exposure, heat, etc)
2. Metal Choices
A. Make allowance for inevitable corrosion and its rate.
B. Ensure galvanic compatibility.
3. Inspection and Maintenance (As 72 points out, the designers really intend certain fasteners to be periodically replaced)
I am still stuck trying to get the original ba***rd things OUT of my GS...The allen hex heads are rounded totally and so far all attempts with sawed slots in them or get vise-grips on have failed totally. I have a mate who is going to help me weld some bar onto them to try to get them turning, or maybe just grind the heads off and drop the whole engine onto a drill press to get stud extractors into the remainder on the bolts. Not even going to bother considering what to replace them with till after, but my tentative options are simple A4 stainless allen bolts or stainless studs with brass nuts if I feel fancy.
What we really need is an authoritative article directly on the subject of best fasteners and practices for aluminum engines. I have not been able to find that, but I have found a bit more useful information.
Racetech Titanium is an American operation that makes mostly titanium fasteners, but also some aluminum. Their website is:
https://racetechtitanium.com/index.php?main_page=index&cPath=143_36&zenid=f5a28c27a93720aad02bb9790955dc4d
I talked to them hoping for information on aluminum bolts for the GS500 headers, but they don't make anything that fits. Their specialty is titanium bolts aimed at motorcycle racing for weight reduction, mostly motocross, where they say they are in almost all the equipment. Titanium is even harder on aluminum than stainless, but in in this application that is acceptable because:
1. They don't expect long service life from racing engines.
2. While that engine is in service, it gets a ton of maintenance. The titanium bolts are in and out all the time, and every time they go back in they get a new application of anti-seize, which should provide at least a period of corrosion inhibition by blocking water penetration.
For general purpose corrosion information, the British operation "Corrosion Doctors" is excellent. In particular one page on their site has a number of downloadable pdf's on different aspects of corrosion control. That page is: http://www.corrosion-doctors.org/InternetResources/NPL.htm#Control
I still have found nothing to indicate that Suzuki's strategy of a zinc plated sacrificial anode bolt that is periodically replaced was not a sensible approach. Sealing off a stainless stud may do fine also, but we don't have any data. Sledge has had unsealed stainless studs in one machine for many years, but we don't know how the aluminum threads are really doing (they might just crumble to pieces if the stud is ever removed).
Quote from: sledge on August 24, 2018, 03:06:06 AM
Anyone else remember Dennis?
He thought he was an Engineer too!
http://gstwins.com/gsboard/index.php?topic=68354.0
:D :D :D
Wow blast from the past.
BTW I dingle balled those walls, and it's still going strong. I think like 120PSI on the cylinder. :laugh:
Don't tell Dennis, he will throw a fit :D
The main professional organization for corrosion engineering is the National Association of Corrosion Engineers at:
https://www.nace.org/home.aspx
Lots of good material here, but I did not see anything specifically aimed at fasteners for aluminum engines in the main material or public white papers. However, since I am not a member, I don't have access to the thousands of articles published in their several journals over the years. More authoritative answers on best material and practices for aluminum engines are probably in there, if we can locate someone with access.
The recommended provider for the stainless steel exhaust studs in the U.S. was referenced via eBay link as "Jon's Auto Shack", where I ordered the studs I now have. I pinged the owner for his understanding of the corrosion problem and the particular stainless he used. He provided the thoughtful reply below:
"Good morning,
I would like to apologize for the few days late reply as things didn't go as planned on Friday and I wasn't able to get back to you as I said.
The 'off road only' reference is just as you said, legality. Since this item (along with others that I make/sell) can be construed as being part of the emissions system, I need to include it so I don't get in hot water with anyone doing modifications of their vehicle.
As for the quality of the studs, these are A2-70 stainless. This means they have a composition of approximately 15%-20% chromium and 15%-19% nickel, which is higher than your typical 304 stainless.
I completely understand your concerns with the galvanic concerns. This comes up almost every time someone goes to replace their OE studs with what they are hoping to be longer lasting stainless. This is one of the reasons I include the copper anti-sieze with the kits. The combination of both the copper flecks (an inert metal that helps isolate the stud from the threads) combined with the solution that it's suspended in, helps act as a dielectric barrier to further help prevent this galvanic issue.
Typically speaking, unless you don't ride often enough, let the vehicle sit for extended periods of time, or live in a high salt water area, the hot and dry environment of an exhaust system helps drive water based electrolytic liquids out of these areas.
If you still have concerns with using these in your GS500, A4-70 studs would be the next option as they have an even higher resistance to galvanic corrosion.
I hope this helps and if you have any further questions, concerns, or really anything, please don't hesitate to ask!
- Jon"
This horse has just about been beat to death, but here are a couple of significant inputs to get the issues nailed down for good (I know I've had enough).
First, you guys might be interested in what a PhD level mechanical engineer and materials scientist I used to work with years ago, and tracked down to ask about this issue, has to say about it. This guy is a great mechanical engineer, who specialized in high temperature materials and design and thus had four graduate classes in corrosion (most ME PhD's have maybe one or two), and here is his opinion:
"Interesting and accurate analysis. You are using the galvanic corrosion theory correctly. The Electromotive forces (EMF) tells a lot about a metals stability/reactivity. When you compare the standard reduction potential (as you did) Al vs SS you will find that the Al is most likely to be attacked (higher negativity - thus the anode). So, when your case is out of Aluminum the stainless steel bolts will essentially be inert because ions from Al will flow to the SS screws. Hence, the set-up (Al Case and SS screws) will be very benign especially in the absence of a liquid. The oxide formation on Al is another challenge. Al will form an oxide layer as soon as it is exposed to air. Al is very reactive to O2.
What you have to watch out for is Al+3 ions flowing towards the SS threads which may make it difficult to remove the SS bolts later. For this to happen, the electrons have to flow from the SS bolt head via a medium onto the Al surface. The "galvanic cell" is complete when the ions from the Al are deposited onto the SS threads. Hence, pitting will occur on the Al threads against the SS bolt threads. Oxidation and reduction bi-products only serve to complicate what is going on. With respect to Loctite and other barriers, I have read many corrosion documents that say these barriers work great EXCEPT when the barrier is damaged and the "galvanic cell" can be completed. In doing so, the amount of electrons flowing from the SS bolt to the Al housing will remain the same, but the ion transfer will increase at the defect. In essence, Al+3 ions must balance the flow of electrons (1 Al for every 3 electrons). We were taught to not count ions but consider them charged holes. The number of holes has to balance the number of electrons. So, when you get to the complexity of oxidation and reduction reactions occurring at the same time as positive ions and electrons flowing, you balance the holes and electrons first, then you balance the charged ions to account for all the potential species forming using a ratio based on the EMF values.
In short, you are right, the Al engine block is being protected by the sacrificial zinc coated steel screws. SS screws will have a "long" term negative effect on engine blocks. The reason I brought up balancing holes and electrons is that as the temperature increases more holes and electrons are flowing in opposite directions to complete the galvanic cell when a medium is present. The problem is exacerbated when Loctite or a barrier is used which fails and focuses the ion transport within the failed site. We were told (30 yrs ago), that your better off not using a barrier to inhibit corrosion, because if the barrier fails you localize the corrosion."
Second, Bossard, the large Swiss fastener company, also got back in touch with me today. I spent about 15 minutes on the phone with the senior applications engineering manager who handles their corrosion resistant fasteners in North America. He confirmed also that the zinc plated steel is a deliberate sacrificial anode that is widely used in the automotive industry with aluminum engines. He says anodized aluminum fasteners would have longer service life, but the problems are that the cost is 8X as much, and people tend to forget they are aluminum and over-torque them. Between the two problems, aluminum has just never caught on, even though in an engineering sense there are many low-torque spots where it would be the ideal solution.
I guess that pretty well settles the questions. It's stay with the zinc plated bolts and regular replacement as Suzuki intended, or throw the dice on the aluminum thread corrosion rate that will inevitably occur with stainless. Aluminum could work, but getting the hardware that will fits and remembering to be careful with it are the issues.
Thanks MaxD, I really did appreciate reading all of that.
From a practical point of view, it seems that the zinc-plated steel hardware is sufficient to do the job but may require more frequent replacement to prevent failure due to over-corrosion of the steel part. So again it's neglect of maintenance (unintentional for sure) that creates the perception amongst GS500 home mechanics that these bolts are "weak". OTOH a stainless stud or bolt would be a far longer-lasting fastener but you may wind up corroding the aluminum head which is much more difficult and expensive to replace. In the end the result from a maintenance perspective may be the same: the bolt breaks when you try to remove it.
So the moral of the story is: do frequent inspection of zinc-plated steel bolts and replace once they show any signs of corrosion and your bike will be happy and easy to work on for years to come. Failing that, you likely will break the corroded bolt and have to work to extract it, but resist the temptation to replace the bolts with stainless steel bolts, but rather replace with equivalent zinc-plated steel bolts and reduce your inspection interval to ensure the replacement bolts don't corrode and then fail.
That said, I did put SS bolts in my engine block when the originals broke. I suppose I should revisit that decision. Maybe I need to order a bunch of OEM Suzuki case bolts.
Thanks for working on this very informative thread MaxD! I have also heard folks saying that they would never use stainless fasteners or parts as stainless is brittle and can fail due to fatigue in motorbike like environments but have never been able to confirm that in my own research.
72, I personally will probably be laying in a stock of the zinc plated Suzuki OEM bolts, even though they are overpriced at $3 each. Bike Bandit sells a set of 12 Vance and Hines for $5.99 (V&H part number V22533) that their search engine takes you to for GS500 header bolts, but Bike Bandit tells me they are unplated. That may not be right, so I tried to check with V&H directly, but they say they did not intend those bolts as exhaust header bolts, and they could not confirm the plating either. Since so many guys here have reported breaking off these bolts, I'm wary of substitutes. I don't doubt there are zinc plated M8-1.25 substitutes out there that are as good or better than Suzuki OEM for lower cost (bags of 100 in grades 8.8-8.9 are around $0.30 per bolt), but we would need to be quite sure of the quality of the steel. After talking to K&L about their valve shims, I had good confidence their half price substitutes were good quality (their apps support was really alert). I don't have a substitute here that I have reason to trust. Maybe some of the other guys are aware of the steel grade issues involved, and can recommend a cheaper/better substitute.
I wouldn't go any lower than a grade 8.8 (maximum torque very approx. ~25 Nm), as although a grade 5.8 would probably be fine up to ~15 Nm, I'd prefer to over-engineer as there's enough other issues to worry about.
I've been enjoying this discussion too, so got in contact with the Pro-Bolt company I mentioned before (http://gstwins.com/gsboard/index.php?topic=72638.msg874782#msg874782). A member of their 'Business Support & Product Development' team responded with:
Quote from: Pro-Bolt
Whilst your OEM torque settings fall within our guide, I would not recommend aluminium for replacement exhaust headers bolts. We have not tested this material in this application and my concern is that prolonged use at high temperatures may cause fatigue. I think you would be better using a Stainless steel or Titanium equivalent replacement with copper grease applied to prevent galling.
Quote from: max on August 28, 2018, 01:02:39 PM
I wouldn't go any lower than a grade 8.8 (maximum torque very approx. ~25 Nm), as although a grade 5.8 would probably be fine up to ~15 Nm, I'd prefer to over-engineer as there's enough other issues to worry about.
I've been enjoying this discussion too, so got in contact with the Pro-Bolt company I mentioned before (http://gstwins.com/gsboard/index.php?topic=72638.msg874782#msg874782). A member of their 'Business Support & Product Development' team responded with:
Quote from: Pro-Bolt
Whilst your OEM torque settings fall within our guide, I would not recommend aluminium for replacement exhaust headers bolts. We have not tested this material in this application and my concern is that prolonged use at high temperatures may cause fatigue. I think you would be better using a Stainless steel or Titanium equivalent replacement with copper grease applied to prevent galling.
Oh yea aluminum bolts will not work. You really want titanium, but an even better idea would be those hollow bolts they seem to have slapped on sport bikes to reduce weight. My SV is full of em. The best feature of those is 2 fold or even 3 fold.
1. Is that they are extremely high quality.
2. They are predrilled. Easy to put in an extractor.
3. They can be sprayed with pb blaster on a weekly basis when in use, and you would get excellent thread penetration cos you can stick the straw inside and spray it, and then plug it with a rubber plug so the pb blaster cane all leak out.
Cool.
Buddha.
Max, thanks for the info on Pro Bolt. The fact that the engine is aluminum is proof positive that the right alloy of aluminum can take the heat, but of course it is true that a particular bolt may not be made of the best alloy for high heat. Basically that's why I am wary of just general purpose zinc plated steel bolts--they may have thinner zinc and not be metallurgically suitable for high heat.
Buddha, titanium is used a lot on aluminum racing engines that have short life and a lot of maintenance, but galvanically it is even harder on aluminum than stainless steel.
Here is an enlightening professional website page for exhaust system fasteners from a large manufacturer specializing in high performance alloys:
https://www.cartech.com/en/alloy-techzone/technical-information/alloy-selection/selecting-high-temperature-alloys-for-fasteners-in-automotive-exhaust-systems
At the bottom the authors of the page are listed--two professional metallurgists. From this page: "Note that CarTech A-286 is used for a wide variety of bolting applications. The alloy is commonly used for fasteners requiring high strength and corrosion resistance in temperatures up to 1300ºF (700ºC). It combines high strength at elevated temperatures with an intermediate Ni level, between CarTech 431 stainless and CarTech 80A alloy. This combination makes it an appealing alloy for a variety of exhaust bolts."
This page has a lot of alloys listed in both table and figure form for these high heat exhaust applications. There is an excellent summary figure I tried to copy and paste, but apparently I don't know the trick to paste the image.
Seems pretty clear from this page that it is probably not a good idea to throw just any old bolt in there--these parts are engineered to this task. I know that thinking much about it seems like overkill. But, outfits like this are not paying dedicated pros just for fun--history has proven to them they need to make that investment. It would be very interesting to see what alloy the OEM Suzuki bolts are and compare it to the alloys listed here.
Quote from: MaxD on August 28, 2018, 11:26:07 AM
72, I personally will probably be laying in a stock of the zinc plated Suzuki OEM bolts, even though they are overpriced at $3 each.
Yeah I wasn't thinking of exhaust bolts, my originals are fine. But I did replace ALL of my engine side cover bolts with SS about a year ago because several of the originals broke when re-installing them after doing a gasket replacement and I was concerned about them breaking again. I didn't consider the galvanic interaction. But we don't have salt water here, I'm not really worried, but if we get a week or two of constant rain and I'm looking for something to do, I might swap those bolts back.
There's no torque on those case bolts. They are barely above finger tight. The big reason to prefer a higher-grade bolt is not for holding torque but in the event of corrosion the torque required to REMOVE the bolt may be too much to keep from snapping the head off of a lower-grade bolt.
72, like the valve shim situation, a quality bolt engineered to the task with heavy zinc plating and made with high temperature alloy is probably out there for half what Suzuki charges. I doubt Suzuki makes this bolt themselves. They probably buy them from several sub-contractors whom they force to compete for lowest price to Suzuki. Those manufacturers probably also provide them to other sales channels who can't get the "OEM mark-up" and must settle for less margin. I just don't know who carries it.
Exhuming this thread as I've been thinking lately and want opinions. If a voltage source were applied across the corroded junction between a zinc plated bolt and aluminum head, could the galvanic reaction be reversed at least somewhat? Perhaps enough to allow clean removal of a bolt that's been cold-welded by nature.
Not sure which polarity you would want or even how to get the current to flow where you want it unless the bolt is already broken off. Nor do I have any idea how much current would be needed or for how long. But this idea keeps rattling around in my head and the noise is getting to me.
Kilted, the use of a deliberately applied voltage is used in marine environments to reduce galvanic corrosion. But, it is in a situation where current flow is very limited by the resistance of salt water between the electrodes. It conducts, but pretty poorly. If you have a bolt in threads that are in galvanic contact, then you don't have high resistance.