As a relatively new GS500 buyer and recent first time poster, I really appreciated all the help figuring out the valve adjustment situation on the GS500. Keeping the exhaust valves shimmed in to the high end of the range to minimize valve recession was a great thing to know.
What I'm wondering now is what other issues like that are out there, the critical other maintenance tips needed to get maximum life out of the GS500. Any other advice from the old pros here who have done the work of figuring out the key issues would be greatly appreciated. If I can get that I'm going to write it up in my maintenance log and keep a special eye on those points. I'd also like to add it to the GS500 Wikipedia article, which could use some improving. I've just done a little editing in the Introduction to try to do the bike justice (providing a pointer to this forum), and would like to add a section on design and maintenance.
I will give you a tip :thumb:
If you can still get the header bolts out do it NOW. Replace them with high tensile studs and stainless or chrome plated nuts and washers
With age those cap heads have a habit of seizing and rounding off. It's perhaps the biggest design fault the GS5 has. Why Suzuki chose this method beats me, probably to save 1\2 a yen.
In 15 or so years time when they need to come off you will thank me :thumb:
Thanks Sledge, they're coming out! Do you have a particular source/brand of replacement you prefer?
After having a look on-line and also searching the forum, it is not immediately clear what are the best materials and sources for replacement header bolts or studs. The Clymer manual does not even give the size of these bolts. One thing that struck me from the comments here is just how bad the header bolt corrosion problem is--some guys are describing these bolts as falling apart. That makes me suspicious it is more than just rust and may also be an issue of galvanic corrosion due to dissimilar metals--aluminum and whatever the bolts are plated with. This would be especially bad if the bolts are splashed with salty water that penetrates into the threads.
Checking galvanic potentials I note these differences:
1. Aluminum and nickel plated steel: ~0.65V (bad for galvanic corrosion)
2. Aluminum and tin plated steel: ~0.3V (pretty good compromise for rust and galvanic)
3. Aluminum and stainless steel: ~0.4V (pretty fair compromise for rust and galvanic)
This aluminum to steel junction has historically been a problem. The U.S. Navy has had tremendous recent problems with aluminum hulled vessels and steel bolts. If Suzuki here used nickel plated steel header bolts in these aluminum threads, that would explain the extremity of the problem. If those bolts are tin plated the problem should have been less, unless the tin plating is so thin that it is quickly consumed by a galvanic corrosion, which then allows the steel to rust away.
Off the top of my head I would guess the best answer is the stainless steel studs and nuts, since you don't have to get the studs out to remove the manifold. The SS studs may corrode in the aluminum threads, but may still last longer than the life of the bike. It might also be a help to use an anti-oxidant compound on the studs or bolts when first installing them. Checking on-line, I don't see anything on whether Loctite serves as an anti-oxidant. Anti-seize compounds often advertise themselves as anti-corrosion and salt resistant, so that sounds like they have anti-oxidant properties.
Question - when you say header bolts these are the exhaust pipe clamp bolts?
When I had to replace the header studs on my last Yamaha, the OEM replacements were zinc coated, which I believe is the common protection method.
Zinc and aluminium have the closest electrode potentials, reducing galvanic corrosion, but not being rust-proof the studs/nuts/bolts will still eventually just rust in-situ instead.
+1 to replacing with stainless if you can get them out (do it before they get as bad as mine!). A2 (stainless 304) is supposedly slightly less likely to fatigue crack than A4 stainless (316), and the clamping load is low so I'd recommend A2 studs and nuts.
Anti-seize or thread locker on header bolts/studs is an ongoing controversy. However, assuming they're correctly temperature rated, either should provide some barrier to reduce galvanic corrosion between the stainless steel and aluminium header if you're that worried, but someone with some more long-term experience might have better insight for you.
Quote from: Jimbob on August 18, 2018, 04:41:45 PM
Question - when you say header bolts these are the exhaust pipe clamp bolts?
That's my interpretation of it.
Jimbob, I assume so. I'm going by Sledge calling them header bolts when he noted that this is a common and very troublesome problem that is worth heading off early. My Clymer manual does not give them a name. The apparent problem is that they often are so weakened by corrosion that they sheer off, and then you have an expensive repair job on your hands.
If they are stuck, this video (https://www.youtube.com/watch?v=3GYzpdtuoVo) shows a way to loosen them with a torch--heat them for about 30 seconds, then gently unscrew them. I assume this works because the thermal expansion of aluminum is about twice that of steel, so even though the bolts expand the aluminum they are screwed into expands even more and opens up.
Max, thanks for the excellent tip on the particular best stainless steel. I'm hoping for somebody to tell me the exact size and source for studs and nuts, but if I had not heard that by Monday I'll see if the local Suzuki shop keeps that information. I did see on Amazon that there are high temp anti-seize compounds, if someone does not want the studs loctited.
From Wikipedia I get the following galvanic potentials to keep in mind: Aluminum at ~-0.9 to -0.95, plain steel at -0.85, stainless steel at ~-0.6 to -0.5 depending on chromium content, carbon steel ~-0.6, copper at -0.35, brass and bronze at -0.4, zinc plated at -1.25, tin at -0.65, nickel at -0.30.
So, if Suzuki is using zinc plated bolts, the difference to aluminum is about 0.25 to 0.3V. That's pretty good, and certainly better than nickel at 0.6 to 0.65V. But as you say, once the plating of any of the zinc or nickel or tin are galvanically corroded away, then you're into a fast rusting process.
I recently saw a book titled "Rust: the Longest War", which is astonishingly well reviewed for a book literally about rust. It points out that the annual damage caused by rust and galvanic corrosion is hundreds of billions of dollars a year. Really a big problem that can only be limited and not solved.
It's an awful issue. The header bolts on my old 45k miler were not even bolts anymore. There was nothing recognisable as 'bolts', just a few lumps covered in flakes of rust.
Where would you source some SS studs and what size?
I updated the wiki with the size, lemmie cut and paste lol....
They are M8-1.25mm.
60mm for the length was confirmed I think by someone in the facebook group for the stock exhaust. Mine are 50mm cuz I have aftermarket pipes.
You should double-check for yourself what would work though. I do know from my project thread that if you stick a screwdriver or whatever into the holes, the depth is 25mm. Then just add on whatever extra length you'd need to go through the stock mounting bracket things and have extra length for the nut.
I bought mine on eBay but that seller doesn't have them listed anymore :technical:
Type M8 stainless studs into ebay and go from there :dunno_black:
Another common problem is the front engine mount bolt seizing in the engine mount. These seized bolts are due to neglect of the motorcycle more than poor design IMO.
If you pull these bolts every 12 months and use an anti seize compound there is no issue.
Quote from: ShowBizWolf on August 18, 2018, 11:16:49 PM
I updated the wiki with the size, lemmie cut and paste lol....
They are M8-1.25mm.
60mm for the length was confirmed I think by someone in the facebook group for the stock exhaust. Mine are 50mm cuz I have aftermarket pipes.
You should double-check for yourself what would work though. I do know from my project thread that if you stick a screwdriver or whatever into the holes, the depth is 25mm. Then just add on whatever extra length you'd need to go through the stock mounting bracket things and have extra length for the nut.
I bought mine on eBay but that seller doesn't have them listed anymore :technical:
This (https://www.cmsnl.com/products/bolt_071200840a/#.W3kjZ72xU0M) is the OEM bolt for the exhaust headers. Obviously, you'd need four. :)
Thanks ShowBiz.
A package of 5 of M8-1.25 X 60mm stainless steel bolts that seem an upgrade from stock can be had from Amazon for $8.65. Link is:
https://www.amazon.com/DIN933-Stainless-Steel-Hexagon-Screw/dp/B015A39NUY/ref=sr_1_9?ie=UTF8&qid=1534663558&sr=8-9&keywords=M8X1.25
This ARP 400-8005 M8 x 1.25 x 57mm Stainless Steel Stud Kit - 4 Piece looks nice for a stud upgrade with stock manifold, comes with 12 point nuts, 57mm seems about right for stock, but price is $38 at Amazon:
https://www.amazon.com/ARP-400-8005-1-25-Stainless-Steel/dp/B003TPLKF2
Sarasi, thanks for that OEM header bolt reference. It looks zinc plated--too bad they don't say.
Crackin, thanks for the note on the engine mount bolt. That goes right into my list also.
I'd personally never want to go back to bolts, no matter what they were made of or how much less they cost than studs.
The whole point of the studs is so you don't have to be messing with the part that threads into the engine anymore when removing the exhaust... you're only working with the threads on the stud and the nut to remove the pipes instead.
I couldn't find in that amazon listing how long the threaded portions are... the ones I bought were all thread. Now I'm wondering how hard something like this could be to find again! I'm gonna heat up my coffee and have a look around for something similar to what I bought.
EDIT: The seller I bought mine from has them again. Here's the link:
https://www.ebay.com/itm/Stainless-Steel-Exhaust-Manifold-Header-Stud-Kits-Metric-M8-x-1-25mm-A2-70/232494547577?hash=item3621c14279%3Am%3Am-Mr12zU3b744btJcTqv6Jw&var=531805757485
Thanks Showbiz, those look nice and about 60% of the Amazon price, with complete threads.
On one of AdidasGuy's nice YouTube videos on putting an aftermarket Motad stainless steel exhaust on a GS500 (https://www.youtube.com/watch?v=4eMGNolMuEU), I noted that new probably stainless steel bolts and header clamps came with the exhaust system. He also used anti-seize and not Loctite on those header bolts.
But, it seems that Motad has gone under. I don't see any complete Vance and Hines systems either.
Are we now stuck with only these quick to rust soft steel OEM exhausts for the GS500?
We aren't stuck :cheers: Here is the wiki link with some options for our bikes:
http://wiki.gstwins.com/index.php?n=Upgrades.Exhaust
Those are the ones I was able to find. If anyone else has any links etc, I'd be glad to add them to the wiki.
I put an RVS Delkevic pair of headers on mine, combined with a (now discontinued) Laser muffler. Main reason is that Delkevic is way cheaper, but I needed something E-approved to be able to legally ride around in my neighbouring country, Germany, and none of Delkevic' stuff is E-marked. The Laser muffler was. But you can combine any muffler with the Delkevic headers obviously. :)
I bought my stuff from here: https://www.uitlaatstore.nl/webshop/303061-suzuki-gs500
It's a one man's shop so he might be willing to ship it to you if you contact him and ask, but I can't say for sure obviously.
Quote from: MaxD on August 19, 2018, 01:38:20 PM
He also used anti-seize and not Loctite on those header bolts.
Don't put anti-seize on header bolts, or any other torque critical fastener :cookoo:
If you lubricate threads it reduces the amount of torque needed before they yield meaning if you do apply the recommended amount of torque you will weaken the bolts or strip the threads because of the now reduced amount of friction between the male and female. If you do then reduce the amount of torque applied you also reduce the clamping force between the port and flange meaning the gasket will be prone to leak and the bolts themselves may even loosen off due to the heat cycles.
I had this argument with him when he was alive, he wouldn't have it. I hate to think how many people took his advice on board and went on to have problems because of it :dunno_black:
Going for the eBay penny pinching prize, I'm gonna try this...
https://www.ebay.com/itm/263307585860
https://www.ebay.com/itm/253539179260
Stainless studs and acorn caps for about $12 :D
Quote from: sledge on August 19, 2018, 02:27:59 PM
Quote from: MaxD on August 19, 2018, 01:38:20 PM
He also used anti-seize and not Loctite on those header bolts.
Don't put anti-seize on header bolts, or any other torque critical fastener :cookoo:
If you lubricate threads it reduces the amount of torque needed before they yield meaning if you do apply the recommended amount of torque you will weaken the bolts or strip the threads because of the now reduced amount of friction between the male and female. If you do then reduce the amount of torque applied you also reduce the clamping force between the port and flange meaning the gasket will be prone to leak and the bolts themselves may even loosen off due to the heat cycles.
I had this argument with him when he was alive, he wouldn't have it. I hate to think how many people took his advice on board and went on to have problems because of it :dunno_black:
It might be the wording, but I disagree that reducing the torque will reduce the clamping force (assuming higher torque dry threads vs lower torque lubricated threads).
Tensile clamping load and fastener torque are usually empirically related by
Load = Torque / (Thread diameter * K), where K is basically a friction coefficient (K
dry > K
wet). So you can obtain the same clamping force for a dry vs wet thread by respectively increasing or decreasing the torque on the fastener.
Of course we're assuming all parts are within their elastic ranges and ideally we would just be measuring bolt strain rather than torque in the first place etc etc.
Completely agree re anti-seize increasing the chances of bolts loosening due to vibration and heat-cycling, and let's not forget that thread locker will also initially act as a lubricant so any torque values used should also be marginally reduced.
I'm of the opinion that the stainless hardware should be fitted dry into the head as the galvanic corrosion is unlikely to have any significant impact - in fact a small amount would be beneficial in ensuring the fasteners don't work themselves loose as discussed.
A closing note for completeness sake, but stainless shouldn't be used for any high-torque fasteners anyway. A2-70 stainless only has a ultimate tensile strength of 700 N/mm
2 which is much lower than than the grade 8.8 or 10.9 steel fasteners used in the more heavily loaded components.
Related to this, but more on-topic to the thread, I've been slowly replacing the non-critical fasteners on my bike with stainless ones because of my pure hatred for rounded and/or Phillips drive fasteners! I'll be slowly updating the wiki (http://wiki.gstwins.com/index.php?n=Restoration.BoltSizes), with my measurements as I progress if anyone ever fancies doing the same.
I'm not a mechanic, so can't easily sort out the conflicting advice from experts like Sledge and Adidasguy. What they have done has worked out well for them.
I do like seeing the math presented by Max, which seems to indicate that if you are careful with torque the anti-seize is OK. I would assume that if you check your header bolt torque pretty regularly, like every time you lubricate your chain, that anti-seize or nothing at all (as preferred by Max) are probably OK.
But, here is a pretty professional reference that leans to using Loctite: https://www.bmw2002faq.com/articles.html/technical-articles/engine-and-drivetrain/installing-exhaust-manifold-or-header-studs-r30/
This is a BMW car article, but it makes a good case as follows for how to best install header studs. First, tighten the stud only finger tight, but use Loctite. It then goes on: "So, why is it wrong to tighten the stud into the hole? Unfortunately, I have even seen it done by supposed "professionals". The way a stud can outperform a bolt in clamping efficiency has to do with the even distribution of stress across the engaged threads. If you torque a stud into a blind hole, you lose that benefit, and concentrate stresses at the first thread in the hole. If you torque the shoulder of a stud against the edge of a threaded hole, you lose the benefit & usually distort the mating surface. It's not as if there is a suitable bearing surface to take the load. Just don't do it. Loctite threadlocker is the answer for securing the stud (for most of our situations)."
So, what this BMW author is saying is that if the stud is tightened down, then when the nut over the clamp is tightened it pulls only against the first one one or two threads on the stud. I assume this could pretty easily bend them for aluminum threads. But, if the stud is a little loose, then the nut exerts an outward pull on the stud that is engaged over most of the threads in the aluminum cylinder head, with much less likelihood of bending the threads.
Based on that, I think I'll go with Sledge and BMW on using the Loctite. For the OEM bolts the Loctite may later increase the risk of breaking a badly corroded bolt, but for higher quality stainless steel studs that corrode slowly and where that rate is further reduced by the Loctite, they can probably be gotten out later if need be.
Endopotential, I looked at those ebay studs, and they are 40mm. It was reported earlier in this thread that for stock headers you need 60mm. I measured on my own stock headers, and if the hole is 25mm earlier reported, then I measured a need for 55mm minimum on the stud.
Quote from: sledge on August 19, 2018, 02:27:59 PM
Quote from: MaxD on August 19, 2018, 01:38:20 PM
He also used anti-seize and not Loctite on those header bolts.
Don't put anti-seize on header bolts, or any other torque critical fastener :cookoo:
If you lubricate threads it reduces the amount of torque needed before they yield meaning if you do apply the recommended amount of torque you will weaken the bolts or strip the threads because of the now reduced amount of friction between the male and female. If you do then reduce the amount of torque applied you also reduce the clamping force between the port and flange meaning the gasket will be prone to leak and the bolts themselves may even loosen off due to the heat cycles.
I had this argument with him when he was alive, he wouldn't have it. I hate to think how many people took his advice on board and went on to have problems because of it :dunno_black:
I see what you're saying and agree. To re-state, since there seems to be some dispute on the point: Clamping force of a bolt is a direct function of turning, of which torque is simply a relative measure. Lubricating the threads makes them turn easier, no brainer there. With a lubricated fastener, the same clamping force will be achieved with the same amount of turning but at less torque. To achieve the same torque requires more turning. The potential for over-clamping (warping parts), stretching or breaking the fastener, and/or stripping threads is quite real.
Torque specs are always assumed to be dry unless otherwise specified.
If you're concerned about it, maybe the best solution is to add it to your annual winter maintenance. If you insist on using compound to save yourself 15 minutes a year, you should reduce the torque. By how much? I have no idea! Swapping out the exhaust studs for stainless does sound like a great idea though.
Quote from: MaxD on August 19, 2018, 05:40:53 PM
Endopotential, I looked at those ebay studs, and they are 40mm. It was reported earlier in this thread that for stock headers you need 60mm. I measured on my own stock headers, and if the hole is 25mm earlier reported, then I measured a need for 55mm minimum on the stud.
I have stock exhaust headers, and took out my bolts to check. The threaded section on them is 40mm long, which seems like plenty. I can't image there's an extra 20mm of threaded hole in the cylinder head.
I'll let you know once the mail from China arrives in 2 weeks or so...
Endo, I took this measurement again. From the face of the hole in the cylinder outward through the collar to the TOP of the bolt head I measure 32mm (I had 30mm the first time I tried this). I measure the bolt head as 8mm, so the collar is thus about 24mm. The hole (which I have not measured) is reported as bottoming at 25mm, though it is not a given that the threads go all the way to 25mm.
So, your 40mm thread should go about 40 -24 = 16mm into the cylinder. That seems like plenty of mated thread to me. So, I retract the link to the Amazon 60mm bolts--I was wrong to assume that 60mm studs also meant 60mm bolts.
The stud situation would seem a little different. The minimum length of the stud IF the stud screwed all 25mm to the to the bottom (I don't know yet if it can) and if the nut used is as thick as a bolt head would seem to be 25 + 32 = 57mm. The members here have several times quoted 60mm, which would then let about 3mm of stud thread come through the nut after it was tightened. That 3mm would allow a washer under the nut if desired.
But, if the stud is only screwed in about the 16mm that your bolts apparently go in, then the minimum stud would be 16 + 32 = 48mm. If the 60 mm stud goes in only 16mm like the bolt, then the stud is going to protrude about 60 (total) -16 (into cylinder) - 32 (collar + nut) = 12mm above the nut.
We have about 10mm variation here depending on how far the new stud is screwed into the cylinder. If it only goes 16mm in, we could probably get by with a 50mm stud.
http://www.zerofast.com/proper-bolt-torque
Explains it better than I can
Sledge, the torquing issue as described in your article pointer above is obviously critical for the case of header bolts.
But, what is your advice on header studs? I assume you saw the pointer to the BMW article above that recommends just tightening header studs finger tight, but with Loctite to prevent them coming loose, and then allowing the tightening of the nut to tension the stud against nearly the full length of the cylinder threads. Did you agree with that?
all this talk about bolt torques, Just use the grunt system.. soft grunt, 20ft.lbs. medium grunt, 45ft.lbs. heavy grunt, 70ft.lbs. Swift kick, 200ft.lbs. :laugh:
IIRC, when I installed my studs, they wound/threaded in the full 25mm and bottomed out there.
J_Walker, that's funny stuff :D
Thanks Showbiz. It seems we have all the information we need to do a perfect job on studs replacing bolts, with the exception of just how tight those studs should be torqued in. BMW says finger tight, but unless I hear otherwise I'll do 'em a little tighter than than, with Loctite on about the first 12mm of the 25mm so that the chore of possibly getting them out later is not severe.
One more piece of information could be useful here--which version of Loctite so that it holds but you can still get it out later. Here's a mechanical engineer's posting on this issue:
"There are different type of thread lockers that are used to basically 'lock threads' of the bolt from loosening due to vibrations. Depending on the thread locker used and the size of the bolt to be loosened, the method to loosen the bolt varies.
If it is a low strength or wicking type thread locker (ex. Loctite 222), simply applying some extra torque using a spanner or screwdriver would do the job. (Generally used for small size screws and bolts)
If it is a medium strength or 'blue' thread locker (ex. Loctite 243) , simply applying the breakaway torque with a torque wrench or pipe would loosen the bolt. (Generally used for medium sized bolts )
On the other hand if it is a permanent strength 'red' thread locker (ex. Loctite 270), you would need to heat the assembly and then apply torque to loosen the bolt. Should do your job :)"
Apparently if you using the "red" stuff, Loctite 270, better have a torch handy to get that stud out.
Holy cow, the red stuff is like welding it in. Posted directions for removal as follows.
"Attempt to remove the bolt first with the correctly sized end wrench or socket. Purple 222 will break free with 20 foot-pounds of torque or less, while Blue 242 will hold to about 50 foot-pounds. If you've got red Loctite, don't bother trying to break it free; Red 271 is rated for about 3,000 psi of shear strength.
Break out your propane or acetylene torch. If you're using acetylene, you need little more than a smoky, yellow "starter" flame to heat the Loctite to its 550-degree-Fahrenheit melting temperature. The yellow starter flame provides more than enough heat to do the job.
Apply heat to the bolt head or stud with your torch, just touching the metal with the end of your flame. The trick here is to keep the torch moving around the bolt or stud to evenly heat it, and not to get in a hurry. It's best to avoid heating the bolt up any more than necessary, and to give the heat a little time to work its way down through the metal and to the Loctite. Some like to heat the bolt to a dull red to be sure, but that's a bit overkill.
With the bolt still hot, extinguish your flame and immediately fit the proper socket or wrench with a long breaker bar attached. Apply steady pressure, and the bolt should come free with little more than the amount of torque it was originally tightened to."
Quote from: sledge on August 19, 2018, 11:36:26 PM
http://www.zerofast.com/proper-bolt-torque
Explains it better than I can
That article's conclusion is the same as how I was trying to, maybe badly, articulate my understanding, so looks like we're in agreement after all!
Quote from: MaxD on August 19, 2018, 05:24:42 PM
... https://www.bmw2002faq.com/articles.html/technical-articles/engine-and-drivetrain/installing-exhaust-manifold-or-header-studs-r30/
...
Quote from: MaxD on August 20, 2018, 01:47:48 PM
... BMW says finger tight ...
Just for clarification, I'm not sure that article is written or endorsed by BMW in any way? "Collinster742002" seems to just be an enthusiast like us all posting this "John Aho"'s article. I take anything online with a pinch of salt so was just wondering whether there was a source reference behind this as I couldn't find one.
Re loctite, the main controversy is the fact that even the "high temperature resistance" LOCTITE 272 still only has an upper service temperature of 200
oC (http://hybris.cms.henkel.com/medias/sys_master/root/h67/hca/9179859583006/Industrial-Product-Selector.pdf). Its technical data sheet (http://tds.henkel.com/tds5/Studio/ShowPDF/272-EN?pid=272&format=MTR&subformat=REAC&language=EN&plant=WERCS) also claims only needing to heat the fastener to 250
oC for disassembly. Both of these temperatures are much lower than the exhaust manifold can reach which brings into question whether the thread locker will be doing its job or just burn.
However, I like the idea suggested in John Aho's article of using Loctite for "just one drop on each clean, dry, new stud", and hand screwing in the studs, then allowing it to set before tightening the nuts. This should stop the stud from rotating as the nut is tightened.
Max, with the issue of whether the Loctite even works for this application on the table, I ran an experiment on the temperature. I used a DMM with a temp probe to find these temperatures on the header bolt and collar:
After 2 minute of idling: 168degC / 336 degF
After 5 minutes of idling: 203 degC / 396 degF
Then 10 minutes of riding, hop off and measure while idling: 202degC / 394degF
The data sheets I have for both Loctite 271 and 272 say a service range of up to 149 degC / 300degF. But, they also say the removal temp is 250 degC/ 482F.
So, it seems that after the temp settles we're typically a little over 200 degC and are out of spec on the high temp Loctite. But, we're still about 45 deg C below the removal temp. We seem to be in a gray zone where it is sort of working, probably relaxing and then re-hardening every time we run the bike.
We have these other options instead of the marginal 271/272:
https://www.lawsonproducts.com/lawson/246-High-Temp-Medium-Strength-Blue-Threadlocker/1383604.lp
Loctite 246 medium strength to 450 deg F (we're at about 400 degF)
https://www.lawsonproducts.com/Loctite/2422-Ultra-High-Temp-Blue-Threadlocker/1383606.lp
Loctite 2422 medium strength ultra-high temp to 650 deg F (might be pretty hard to ever get off)
Wow, this thread has definitely wandered off from general maintenance, to a graduate level discourse on studs and Loctite!
Still fun and learning a ton regardless :cheers:
Endo, sorry for it to get so long. That's happened because Sledge reported this header bolt severe corrosion problem as probably the most serious design flaw on the GS500, but one that should be correctable with stainless steel or chromed hardware. He's an expert and I believe him. But, then it gets deep because we have galvanic corrosion material choice issues because the cylinder head is aluminum and does not really match up with anything, there are different grades of stainless steel to be aware of, the decision as to whether to use bolts or studs/nuts, the decision as to whether to use Loctite or anti-seize (hotly contested among experts), the decision on how much torque to use for each of studs and bolts with nothing, Loctite, or anti-seize (can cause over torquing since you don't really know how much to back off on the torque spec), and then finally the fact that the common 271 grade Loctite does not apparently meet the temperature range needed (good to 300F with us at a little over 400F), and the much less available 450F Loctite 246 being expensive and carcinogenic.
I've ordered a set of SS studs, but am still not sure if that's the best decision or what grade of Loctite (or nothing or anti-seize) to use. If I use available high temp Loctite 271, it's apparently loosening every time the bike is ridden. I don't know how many cycles it can go through before it's ruined and effectively does nothing, so that when the header nuts are periodically tightened it may end up over-torquing the studs in because they are moving also (that would tend to happen with anti-sieze also), which can damage the fragile aluminum threads in the cylinder.
It seems like a simple problem, but really is not. Allow corrosion, bolt breaks. Too tight and may strip threads. Too loose and may burn an exhaust valve. Expensive repairs in each case.
It's making me wonder if the safest thing is to go back to stainless steel bolts, nothing on them to avoid over-torquing them, and just periodically loosen them to break corrosion and then re-torque them to spec. At least then I know what I'm putting on those aluminum threads, unless the aluminum to stainless steel galvanic corrosion is spoiling that! It then leads to thinking again about anti-seize, which may be more consistent for torque than corrosion even though different sources report the need to reduce torque for given clamping by a loose and undependable range of 25% to 50% when using anti-seize.
Those temperatures are interesting, I thought it'd get hotter than that - I love a little experiment. Those Loctites also have better potential, but strangely I can't find a reasonably priced supplier for them in the UK.
When I originally said thread locker and anti-seize on headers were an ongoing controversy that was no joke haha. It's been thought provoking at the very least!
Max, one of my books says the exhaust gas temperatures can approach 1700 degF. The point where I was measuring was the part of collar around the bolt that is on the far side from the exhaust pipe. That's about 1.5cm from the pipe, which is benefiting from the cylinder fins and general heat spreading. I did not try the inside that is about 0.5cm from the pipe because I did not want to ruin my temp probe, which is intended for electronic work and won't stand up to what might be 1000degF (nor will my hands!).
We don't seem to have the engineering data here to make the best call. Suzuki does know, but their decision to use cheap apparently zinc plated steel bolts is apparently flawed. If I were making this call right now myself with this limited data, seeking the most reliable and least risky solution, I would say stainless steel bolts with anti-seize torqued to 60% of recommended dry torque, loosened and re-torqued periodically, and replaced every few years to eliminate corrosion that still occurs even with the anti-seize. Of course, I'm a complete amateur and just about everybody here knows more about bike maintenance than I do. If the 271 Loctite is in fact holding on the far side of the threads from the pipes, then the studs would seem quite safe and more convenient.
I have a professional update on the Loctite for use with the header studs which is not definitive, but which is still fairly supportive of using the studs with Loctite.
I went for advice on this to tech support at Loctite, specifically to support engineer Sylvain Lebel (United States support, sylvain.lebel@henkel.com, 800-562-8483). He has worked there 16 years and has had many calls on the question of using Loctite in these high temp applications. His bottom line summary was that while they do not specifically recommend any version of Loctite for header stud application, that quite a few people including pros are using it for that, and he is not getting any complaints of the studs moving with nut tightening and stripping out aluminum threads. The most common grade used is the widely available Loctite 272. Henkel/Loctite does not warranty Loctite, and users are on their own for all applications.
Further details are:
1. Well above spec range Loctites will "burn" and loose effectiveness. They have not tested for this to report specific consequences. Since they don't warranty, they are not that worried about nailing down the exact consequences.
2. Grip strength degrades fairly linearly with temperature. They spec the range at the point where grip strength is about 50% of room temp.
3. Loctite 272 will have both temperature and age related weakening in this application. After 1000 hours at the high end of the spec range of 272, which he says is actually 450F, the room temp strength will be down to 60% of original. At that use time while at the high end of the temp range, strength will be down to about 30% of room temp original. Sylvain is not aware of the number of cycles being a problem--its a decline based on total time at high temps. When cycled it does not melt and turn liquid, but it does soften into a plasma like state. Apparently it can then re-harden without damage, but this is an assumption (no warranty on cycle count effect).
4. He warns against trying to remove any high strength version at room temp--it can tear aluminum threads. It must be heated to be removed.
5. There are recent higher temp versions of Loctite available. 2422 is a medium strength 650F version (50% of strength at 650F). 2620 is a 650F high strength like 272. These are not as available as 272, but can be had from industrial suppliers. How much they are being used yet for header studs is not known, as they have only been out about 2 years.
6. Loctite in its just applied state does act as a thread lubricant, so reducing torque to about 60% of standard dry torque is recommended. The issue of just how much studs should be tightened in this application (finger tight, a little more, or 50-60% of bolt spec) is still not clear.
So, that gives some support for studs with available Loctite 272. It is not warranteed or recommended, but empirically it seems to be doing OK in the field over a number of years. It may be slipping and tightening the stud on nut torquing if the Loctite is burned, but stripping as a result is not known to Loctite to be a common occurrence. Therefore, it might be safer to use studs with Loctite than bolts with anti-seize or without, because it is avoiding the need to re-torque bolts periodically and thus subject the threads to repeated torque hits.
That's as much info as I know how to get on trying to correct this header bolt corrosion design problem. It seems there is no known highly reliable cure, but we have taken a step in the right direction with either stainless steel bolts, or with stainless steel studs and Loctite 272. In either case we have to check and possibly re-torque either bolts or stud nuts fairly often. We also have to replace bolts when they get significant corrosion. That is presumably what Suzuki was expecting to be done, it was just that their zinc plated bolts probably have to be replaced more often than stainless steel bolts.
Update: See post "Suzuki knew what they were doing after all" for the full story. It is almost certain Suzuki was deliberately using zinc plated header bolts as a "sacrificial anode" to prevent galvanic corrosion of the aluminum threads. Stainless in aluminum will force the aluminum to become sacrificial and corrode. This might be fine for stainless studs, especially if they are well sealed. For stainless bolts that are periodically tightened and sometimes replaced, the aluminum threads are corroding and the time will probably come when they won't hold a new bolt.