Replace rear cam chain guide?

[HPP8140]

Hi,

95GS500E 74K miles

Symptoms:
bike has had initial throttle hesitation below 4k rpm since 40k miles
noticed bike running rough below 3k rpm
noticed bike lacking power during memorial day weekend
parked the bike after 400 mile ride where I noticed fuel starvation and power loss
went to start bike for morning commute and heard clacking...parts hitting
removed the valve cover, turned the engine over by had as I usually do for valve adjustments, found the cam-chain slacking and timing marks mis-aligned

Please help diagnose, looks like it's not worth fixing though.



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[89500inPA]

I would guess your cam chain tensioner has failed and the chain slipped a couple teeth. Probably not broken. It is probably worth fixing if you can, but I never have so let others weigh in first. There is a method for measuring the cam chain for stretch but i think the tension would need to be sorted first. I would also recheck valve clearances to be sure nothing is sticking or too tight. 

[bombsquad83]

It's likely that your valves impacted your pistons, but that's not necessarily game over as long as it didn't wreck too much havoc.  Your bottom end is probably fine.  You need to pull the head to verify the condition of the valves, pistons, and cylinders.  It might not be worth it to you at 74k miles to replace valves, cam chain, and cam chain tensioner.  It depends how confident you are in the engine otherwise.  Does it consume a lot of oil, how was the compression before the cam chain issue, what shim sizes were you down to on the valves, etc...

[HPP8140]

YEAH it consumed oil haha...was topping off after every gas fill up.

Shims were good, no where near the 220 small size.

Need to find a used engine or sell whole bike as parts for cheap

I'm baffled how it ran like this until I parked and the engine cooled.

[yamahonkawazuki]

It's likely that your valves impacted your pistons, but that's not necessarily game over as long as it didn't wreck too much havoc.  Your bottom end is probably fine.  You need to pull the head to verify the condition of the valves, pistons, and cylinders.  It might not be worth it to you at 74k miles to replace valves, cam chain, and cam chain tensioner.  It depends how confident you are in the engine otherwise.  Does it consume a lot of oil, how was the compression before the cam chain issue, what shim sizes were you down to on the valves, etc...

if it were me if digging into top end, what about rings as well, if rest is ok?

[bombsquad83]

If you were dedicated to really fixing this engine, then yes, rings as well.  Might help oil consumption issues.

[MarkB]

YEAH it consumed oil haha...was topping off after every gas fill up.

Shims were good, no where near the 220 small size.

Need to find a used engine or sell whole bike as parts for cheap

I'm baffled how it ran like this until I parked and the engine cooled.

I had the cam chain tensioner fail on my GS500E a few years back resulting in bent valves.  Like you I noticed funny rattling noises while it was running, but the chain didn't skip with the ensuing damage until the next time I tried to start the motor.  Happily, that meant the engine wasn't spinning very fast when things went bad so I was able to just replace the valves (exhaust only as I recall), oil seals, and cam chain tensioner to get it back on the road.  My motor had a lot fewer miles on it at the time, so it was definitely worth saving, but I don't believe the parts were horrendously expensive.

[HPP8140]

YEAH it consumed oil haha...was topping off after every gas fill up.

Shims were good, no where near the 220 small size.

Need to find a used engine or sell whole bike as parts for cheap

I'm baffled how it ran like this until I parked and the engine cooled.

I had the cam chain tensioner fail on my GS500E a few years back resulting in bent valves.  Like you I noticed funny rattling noises while it was running, but the chain didn't skip with the ensuing damage until the next time I tried to start the motor.  Happily, that meant the engine wasn't spinning very fast when things went bad so I was able to just replace the valves (exhaust only as I recall), oil seals, and cam chain tensioner to get it back on the road.  My motor had a lot fewer miles on it at the time, so it was definitely worth saving, but I don't believe the parts were horrendously expensive.

Yeah...as I was turning the engine over by hand I felt resistance of valves probably hitting piston. I'm sure it would run if I just reset timing and cam chain, but probably not worth it and I don't have the know how or desire.

It's good to know these engines will last. Probably could have avoided this if I checked the cam-chain like I religiously maintained the valves.

Yeah, guess I'm lucky, can't count the number of times I started the engine on my 400mile trip the day before I parked the bike safely in the garage and this happened.

How do the Ex valves look? One of them is darker than the other.

[MarkB]

In my case just retiming it wouldn't have done it. The bent valve stem didn't slide properly so the valve didn't close. It probably wouldn't have aligned well enough to seal on the valve seats even if it did go down.

I'm guessing your darker valve is on the cylinder with oil control problems.

[HPP8140]

Well, turns out the sound I heard was not the valves hitting the piston. The timing was only off by 1 tooth.

The cam chain tensioner is also working ok.

The issue is the rear cam chain guide #8 http://images.cmsnl.com/img/partslists/suzuki-gs500-1990-el-cam-chain_bigsue0048fig-11_5815.gif broke in half, so the tensioner had nothing to push up against the chain.


I pulled the broken piece out, but could not pull the entire guide out. Does replacing the rear guide involve splitting the case?

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[Big Rich]

I'm pretty sure you don't need to split the cases for that. Going from memory (but just got off midnight shift......), once you pull the cylinders off you should be able to reach the broken section with some long pliers or a set of forceps. I could be very wrong though.

[HPP8140]

Noooooooooooooo...I don't want to go as far as pulling cylinders. I can reach it with the valve cover and intake camshaft removed.

Guess it's time to look for another GS500.

Any other input?

[HPP8140]

bump

[burning1]

I'm pretty sure you don't need to split the cases for that. Going from memory (but just got off midnight shift......), once you pull the cylinders off you should be able to reach the broken section with some long pliers or a set of forceps. I could be very wrong though.

Pivot for the rear cam-chain gude (CCT side) is on a pivot that fits between the case halves. You don't need to remove the cylinders to replace it, but you do have to flip the engine and split the cases.

[rexpepper651]

sell it to me your gs for 50 bucks and ill fix it lol

[dinkydonuts]

If you live near Oklahoma, I'll be selling my GS later this fall. 04 F model with 11k miles.

[rexpepper651]

dang sucks to hear
im a little too far north lol.

[HPP8140]

Split case? as in remove oilpan?

@dinkydonuts - only interested in pre F models

@rexpepper651 - it will be for sale when I find a replacement minus tank, carbs, bodywork

Funny thing I have a 06 gsxr, but miss the GS

[The Buddha]

Rear guide you have to split the cases to get it out and back in. Its not in the bottom of the cyls, its between the cases about 1" down  ... worthless design ... good thing it only happens very very rarely.
Cool.
Buddha.

[HPP8140]

Just picked up a 2002 GS, now to figure out what to do with the broken 95.