Hi,
Previously I have posted about rev surging issues with my 04 gs500f and I have been looking for an exhaust leak in the system. For the past two months, I have been cleaning and learning about carburetors, changing valve shims, and doing as much maintenance as possible since the bike comes with muddy engine oil. I have just put the bike back together yesterday and the rev surging issue is still there.
the bike previously had a rev surging issue. Now that i have clean the carbs, replace the orings, and changed the shims to specs, the bike started sputtering.
(https://i.imgur.com/YPDLD12.jpg)
I rigged up a setup to test for a vacuum leak: I plugged a hose to the vacuum hose to the engine side of the carburetor (as shown in picture above), try to suck air with my mouth from this hose while covering the airbox side of the carburetor. With the intake valve closed, I can feel that both carburetors hold suction, meaning no obvious air leak. However, when I open the intake valves of each cylinder, the left holds suction and the right does not. With the leaky right cylinder, it was able to hold suction again when I cover not only the airbox side of the carburetor but also the exhaust pipe exit. Therefore I suspect a burnt exhaust valve.
Can anyone tell me if this is a valid diagnosis, and how do I check for the exhaust valve? Also, the shim on the left exhaust valve still has a less than 0.03mm gap after I changed the shim from 268 to 255, does that means I have to go with a thinner shim?
Really appreciate all the help.
Quote from: mentalshark on September 09, 2021, 02:41:53 PM
Also, the shim on the left exhaust valve still has a less than 0.03mm gap after I changed the shim from 268 to 255, does that means I have to go with a thinner shim?
Yes, you need to go down at least one more shim size. You say all your valves are in spec but then you say that one is definitely not in spec so I am confused. On the exhaust valves I shoot for the looser end of the Suzuki spec or even looser. Like .08 - .10. Under .03 is not good. You need to get all the valves in spec before you bother diagnosing the other issues.
The fact that you had to jump so many shim sizes and still aren't in spec isn't a good sign for the health of that exhaust valve.
To check for a bent or burned exhaust valve you could try taking the exhaust off and shining a flashlight down the spark plug hole. Then turn the engine over like you are doing a valve check. Take the valve cover off for even more info. Whenever the cam lobe for the exhaust valve isn't depressing the shim/valve that valve should be fully closed and therefore you shouldn't see any light coming through the exhaust port. Like with the test you described in your post above, you have to make sure that the engine is in the correct part of the rotation for each exhaust valve you are testing this way.
A compression test would be another good test. If compression is really bad and doesn't improve by adding oil to that cylinder you probably have a bent or burned valve.
A conclusive test (but lots of work) would be to remove the head, turn it upside down, and let a puddle of WD-40 sit on the valve surface over night. If any has leaked out the next day then you know you need to do the valves. But at that point the top end is off so you might as well rebuild it anyways.
Surging issue is usually a vacuum leak though. Are you doing these tests that cause surging with the stock airbox and filter installed? Just having the airbox off to save a few minutes of reassembly could be causing the surging.
Have you replaced all rubber parts from the airbox to the cylinder head? Even an 04 is getting old enough to possibly need new airbox boots, rubber carb internals, intake boots, and intake boot o-rings. Did you bench sync the carbs after cleaning and then vacuum sync the carbs once installed?
Hi Bluesmudge thank you so much for your detailed reply.
I have placed an order for a compression test kit and a endoscopy camera and hopefully take a look at the valves from the inside through the sparkplug hole (let's hope the camera is small enough). The exhaust pipe got rusty bolts so I am kinda scared to deal with that. If I can't see the valves with the camera I will take it off and check it. Hopefully I can get a clear sense of what is happening without needing to take the head off. Is a valve replacement a job I can do myself? I researched for a bit and realizing it will need a few specialized tools for the job.
The surging problem previously was fixed by dropping the idle, and I have proceed with a lunchbox air filter and rejet. I guess I will change thing back to stock till I have all these fixed first. I have tested all the rubber parts you mentioned and they seemed ok, no big leak was found. Engine was synced with a home made 2 bottle sync tool but then since the left exhaust valve is still out of spec I will have to resync it. Interestingly the engine sputtering started when it's more synced. The bike had a weak response to throttle and as I was syncing it, it respond better by going a higher rpm with a similar throttle twist, however it also started sputtering and rev surge when the sync is complete.
Quote from: mentalshark on September 10, 2021, 01:42:37 PM
The exhaust pipe got rusty bolts so I am kinda scared to deal with that. If I can't see the valves with the camera I will take it off and check it. Hopefully I can get a clear sense of what is happening without needing to take the head off. Is a valve replacement a job I can do myself? I researched for a bit and realizing it will need a few specialized tools for the job.
Rusty header bolts...I know about that life. I just had 2 bolts break off while removing the exhaust on a 1980 GS1000G. Then proceeded to get a hardened extractor stuck in the stuck bolt and had to grind it out with diamond bits on a Dremel and put in Helicoils. NOT FUN.
Unless something is seriously wrong, I doubt you will be able to see the issue with the camera. The compression test will be your best bet I think. If compression is ok get your valves in spec before dealing with the surging issue. If the compression is real bad you will need to rebuild the top end (no sense in doing all the disassembly work for one valve. Once you are there do all new valves, valve seals, cylinder rings, and deglaze the cylinders).
If it comes to that, can you do it yourself? Thats up to you to decide. Personally, earlier in life when I bent the valve on my GS500 and was short on cash I opted to swap a used head off Ebay rather than rebuild because I wasn't sure I could do it. The parts including the used head was around $200 all in. I learned just enough to not screw it up and got the bike running for another 20,000 miles.
20,000 miles later in life the bike was burning oil pretty bad. Since I could now afford it I had a shop rebuild the top end. That was $2000 including carb rebuild, dyno run, and general tune-up stuff. I live in a relatively high cost of living area, so if you are somewhere with more local mechanics/machine shops it might be cheaper. If I didn't love my GS500 to death it wouldn't have made financial much sense to sink $2000 into a $2000 motorycle. But I have a ton of aftermarket parts and everything set up just the way I like it so it made sense for me to know I have a fresh rebuild good for another 40,000 miles.
You will have to make a similar judgement of your mechanical ability and value of your time and value of your bike. The value of giving it a shot and learning along the way may be worth the money and time even if you end up messing it up. You can always buy another head or entire engine off Ebay for not too much. GS500 parts be cheap!
I thought cylinder rings would need to go deeper than the head rebuild.
I think your plan is a good plan and I intended to follow that plan, I just don't want to take the head off without being certain that the valves are the issues. And yes if I am going in there I might as well do as much as I can.
Your story reminded me why I bought this bike. I bought if for 500 bucks thinking it was just some electrical issues. I want to get something carbureted and air cooler so it would be easier for me to work on it myself. I want to something cheap to learn. I am going to try working on it myself. Like you said the worst case scenario I broke something and I can just get a new head or engine for cheap. Summer is almost over here and winter is not really suitable for riding anyways so I will have a lot of time to work on it.
Thank you bluesmudge
Quote from: mentalshark on September 10, 2021, 06:27:06 PM
I thought cylinder rings would need to go deeper than the head rebuild.
If you already have the head off, doing the rings just means pulling the jugs (cylinder). Other than the rings, it just means replacing the base gasket. Thats why its generally part of a full top end rebuild.
In addition to the Haynes and Clymer repair manuals, beergarage.com is a website the really helped me when I was learning how to do this stuff. It has some great step by step tutorials. Unfortunately, it looks like the owner stopped paying for web hosting in 2018 but you can still access it using the wayback machine (thank goodness for internet archives!):
https://web.archive.org/web/20180523015928/http://beergarage.com/GSHeadOff.aspx (https://web.archive.org/web/20180523015928/http://beergarage.com/GSHeadOff.aspx)
Often beergarage would do things for the sake of being cheap, like making gaskets out of cereal boxes. You will probably want to ignore those parts of the tutorials and order OEM parts from a Suzuki parts dealer.
I just finished watching one of the youtube tutorials on top end rebuild (https://www.youtube.com/watch?v=6X0VwcdZq7M&ab_channel=BaltimoreGS) and now I understand what you mean by having the head off will lead to a piston ring change. Mostly because when I think of a top-end, I was only thinking of the head instead of the head and cylinder block.
Love how the Wayback machine helped me multiple times when I am looking for ancient articles in situations like this. I actually have respect for people making gaskets out of cereal boxes, sometimes it's about making use of what is available on hand and gets the job done. I also do understand why I would want to order OEM parts since they are actually designed for it. What is your opinion on gasket materials? ordering parts from the dealer sometimes takes 1-3 weeks I like to have something done right now instead of having an open engine while I can do nothing to it. beergarage's tutorial looks very very detailed, this will come in handy when I do decide to take it apart. I have actually found what looks like a shop manual here (https://www.manualslib.com/manual/793090/Suzuki-Gs500e.html?page=1#manual) that have a very in-depth description of what you should do deep inside the engine. I am using this to cross-reference with a video I have found online about a certain procedure.
I have decided to take the exhaust off to visually inspect the valves, and yes the endoscope couldn't really see anything. However, I am able to hear the exhaust leaking more than the left side. not touching anything till I got the compression tester kit here. In the meantime I did snap an exhaust bolt, should have been more patient with the bolt, and try to heat it up when applying force. Gonna try to soak and tap it for the next 2 days then try to use a screw extraction tool.
how much thread do you have sticking out? Hit me up if you need help, the DPO on my bike buggered this up big time for me. I've got a few nifty tricks.
about 2mm sticking out, and now has a broken extraction tool in there hahhahahhahahhahaha
(https://i.imgur.com/swAOdfP.jpg)
(https://i.imgur.com/yulgdTn.jpg)
also vice grip coming this afternoon, so if you have something please do let me know
I was about to reply that you should not use an extractor under any circumstance, since I just learned my lesson. Looks like I'm too late.
You need to be extremely prescriptive with what you do next because you may only get one more good chance at solving this before the head needs to go to a machine shop to fix those threads (or buying a good used head off ebay that doesn't have broken header bolts).
The extractor is hardened steel, so you can't drill it with normal drill bits. Be careful if you go with carbide drill bits because those are brittle and if that breaks off in there you are really SOL.
What I did was buy a 90 degree adapter for my Dremel, and a series of progressively increasing diamond grinders/bits. They are generally designed for tile/glass but work well here. I worked my way up to 1/8" and then finished the job with a 1/8" carbide bit. Once the extractor was out I purchased a helicoil kit designed to return the threads to their original size/thread. I worked up from the 1/8" size to the recomended drill bit for the helicoil tap using progressively larger fresh drill bits. Then carefully tapped the hole and installed the helicoil. To do this on 2 snapped bolts took me an entire day (not counting acquiring all the parts/tools). It was very stressful, slow, messy. Learn as much as you can before you start the process and be mentally prepared for the implications if you fail.
Right now I am thinking to try a vice grip (arriving today). If that does not work, hire someone weld a nut, or just buy a welder and do it myself. when those failed I will try the diamond drill bits as you described. When that failed I guess machine shop will be my last stop before buying a head...
Best bet is to get someone to weld a nut on the end (weld from the inside of the nut) the heat helps enormously to release the bolt.
However you can dissolve the extractor, and also the bolt if it is not stainless steel. you have to remove the head, mount it so the bolt faces upwards, make a dam around the bolt with blu tack and fill with saturated alum solution. keep the solution warm, i used an old fashioned filament bulb above to keep it warm. I dissolved a broken drill bit completely in about 3 days. Alum is an aluminium sulphate compound and creates a chemical reaction that eats steel but leaved aluminium perfect.
Hint you can find alum in the canning section of big stores. It is used to make pickles crunchy. So it's not too poisonous ;-)
There are more detailed instructions if you google this method.
Dude this sounds like something interesting, I will look into this! thanks, man!
Quote from: herennow on September 13, 2021, 10:54:01 PM
Best bet is to get someone to weld a nut on the end (weld from the inside of the nut) the heat helps enormously to release the bolt.
However you can dissolve the extractor, and also the bolt if it is not stainless steel. you have to remove the head, mount it so the bolt faces upwards, make a dam around the bolt with blu tack and fill with saturated alum solution. keep the solution warm, i used an old fashioned filament bulb above to keep it warm. I dissolved a broken drill bit completely in about 3 days. Alum is an aluminium sulphate compound and creates a chemical reaction that eats steel but leaved aluminium perfect.
Hint you can find alum in the canning section of big stores. It is used to make pickles crunchy. So it's not too poisonous ;-)
There are more detailed instructions if you google this method.
Wow, that is super interesting. I'll keep that strategy in the back of my mind for the next time something like this happens.
I actually plan to just run a test first. I have some rusty exhaust bolts, a broken bolt extractor shaft, and maybe I can just use one of the cooling fins on the engine block to test out the whole scenario with all 3 types of metal that will be contacting with this alum solution.
Alum, no, I would try whiskey.
Now, How does it work.
Get me some whiskey and I'll not worry about it.
Seriously, I have drilled them out - by taking off the whole front end, and sitting in the space wteh front end was and using left hand drills and going slow. Then tapped it to the next size up - a sae 5/16th IIRC.
Cool.
Buddha.
Quote from: The Buddha on September 14, 2021, 02:48:09 PM
Alum, no, I would try whiskey.
Now, How does it work.
Get me some whiskey and I'll not worry about it.
Seriously, I have drilled them out - by taking off the whole front end, and sitting in the space wteh front end was and using left hand drills and going slow. Then tapped it to the next size up - a sae 5/16th IIRC.
Cool.
Buddha.
Haha yea I am also skeptical about this, because in theory if something that works this well would become widely known thanks to the internet. Now, I am not saying this won't work at all, I have been doing some research on this topic for a bit and there have been a few cases where some watchmakers do this to dissolve broken off the crown stem, with the crown being stainless steel and stem being.... copper? it appears to work on ferrous metal or more reactive metal (https://en.wikipedia.org/wiki/Reactivity_series) but not stainless steel. anyway, I thought it'd be interesting to at least give it a shot since alum is not expensive, and there are rusty bolts, broken drill bits and broken hearts laying on my garage floor.
As I said Carbide drill bit gone in three days with warm solution (not boiling), there was a great write up on Practical machinist blog, but its lost when they upgraded the forum.
I did keep drilling after that as the bolt was stainless, eventually was able to pick out the last bits and just put in a stud permanently.
Ill see if I can find any pics, it was some years ago.
Quote from: mentalshark on September 15, 2021, 10:29:34 AM
Quote from: The Buddha on September 14, 2021, 02:48:09 PM
Alum, no, I would try whiskey.
Now, How does it work.
Get me some whiskey and I'll not worry about it.
Seriously, I have drilled them out - by taking off the whole front end, and sitting in the space wteh front end was and using left hand drills and going slow. Then tapped it to the next size up - a sae 5/16th IIRC.
Cool.
Buddha.
Haha yea I am also skeptical about this, because in theory if something that works this well would become widely known thanks to the internet. Now, I am not saying this won't work at all, I have been doing some research on this topic for a bit and there have been a few cases where some watchmakers do this to dissolve broken off the crown stem, with the crown being stainless steel and stem being.... copper? it appears to work on ferrous metal or more reactive metal (https://en.wikipedia.org/wiki/Reactivity_series) but not stainless steel. anyway, I thought it'd be interesting to at least give it a shot since alum is not expensive, and there are rusty bolts, broken drill bits and broken hearts laying on my garage floor.
To me, if I am pulling the head - there's a million ways to get it out. In fact I'd take it to my engine guy who mainly does cars but he also is a biker and has worked on my bike engines in the past.
TBH, you could try getting to the thing from the side with a dremel tool and a cutting disk and cutting a slot in it dead center, and the easy out should come out - just remember to turn it the right way.
Then see if the bolt bit would come out with more drilling etc etc.
BTW one complaint I have about those easy outs is that they tend to spread the thing you're trying to extract.
Cool.
Buddha.
Well, I have decided to drill it out.
but I did run the test if alum works. and here are the results. Saturated Alum solution, 25C 77F temperature. 24 hours. I did put the cup on top of the hot water pipe hoping it will heat it up, but it didn't.
(https://i.imgur.com/EX0rWbW.jpg)
1.15% weight reduction
(https://i.imgur.com/2INgClQ.jpg)
2.41% weight reduction
(https://i.imgur.com/3ZODQ4F.jpg)
2.53% weight reduction
The contact face of the drill bit in the engine is very small, but heating up the solution will speed up the effect. I do think there is a place for this method in some cases. the best thing about this is that you literally just let it sit and you don't have to do anything.