Problem - exhaust valve rapid recede into head

[HPP8140]

So my right exhaust valve is rapidly receding into the head compared to the other valves. There is slight resistance when turning the bucket, even if there is clearance. The other buckets turn freely. At 30K, I changed to a 240 shim to give me .07mm clearance. Now at 35K, there is no clearance with a 235 shim. I'm going to pick up a 230 shim today to see if I have clearance. What are some ways to slow down this receding process? At this rate, I probably only have 5k left in this engine, but it runs great, only this 2nd exhaust valve wear is the problem.

Thanks in advance.

[The Buddha]

Replace the valve and re do all the seats. I'd venture to guess its a manufacturing defect.
Ry_guy lost a chunk of exhaust valve ... look for his post and check out the pic.
Cool.
Buddha.

[ojstinson]

Keeping the RPMs below 6k, would probably slow the progress somewhat. Some say lead substitutes work----guess it couldn't hurt.


http://www.thumpertalk.com/forum/archive/index.php/t-73319.html



Buddha probably has the best solution---perhaps the only.

[HPP8140]

I think that may be beyond my expertise. Maybe cheaper and easier to look for a new engine?

[ojstinson]

You should try to wring all the milage you can out of it-----just run it till it's shot, what have you got to lose---it might just surprise you.

[The Buddha]

Actually would it be bad really to run pre mix in the gasoline on a GS. Yea motor will smoke ... but it will solve a 1000 problems ... tank rust ... valve and ring/cylinder wear etc etc ...
Cool.
Buddha.

[ojstinson]

That's true, at this point he has nothing to lose-----I've even heard mechanics who swear by Marvel Mystery oil.

[Pigeonroost]

Running a light 2 cycle mix probably won't do any harm, but not sure it would do much good either.  Like Buddha was 'splaining, the most likely cause was a lousy valve to seat seal to begin with and the oil in max might cool the jetting down a bit, but the valve will slill errode.  I vote with having the valve seat re-cut and matching in/lapping a new valve to seal properly.

prs

[Pigeonroost]

That's true, at this point he has nothing to lose-----I've even heard mechanics who swear by Marvel Mystery oil.

Yeah, but carrying around a bottle/can of MMO would be a PIA.  How about the little tear top plastic pacs of air cooled 2 cycle oil sold for weedeaters and such-- could carry a few in a tank bag or such.

prs

[joshr08]

i vote for removing the head and fixing the problem before you blow the motor. do a search and see just how many people are parting out bike because they cant find a GOOD CHEAP or even a GOOD motor at all.  Depending on your riding style and miles you put on the bike in a yr you could wait until the end of the riding season(if there is one in your area) or do it now.  I personaly wouldnt risk ruining a perfectly fine motor because i didnt want to fix a valve problem that i know to exist. just my .02 just remember its alot cheaper and easyier to fix a small problem that it is to fix a big one.

[gsJack]

Increased exhaust valve clearance allowing the valve more cooling time on the seat seems to be very effective in extending GS valve life.  I had one exhaust valve on my 97 GS down to a 215 minimum shim at 76k miles.  It started it's fast regression at about 40k miles after running at a minimum clearance for over 30k miles before that.

My 02 GS had an exhaust valve starting to receed at 30k miles after running at minumum clearance for many miles.  I increased the clearance to .005" (.012 mm approx) at about 40k miles and it still had .004" clearance at about 60k miles and now at almost 70k miles it stills idles smooth cold indicating it still has clearance 30k miles later.  It's time for my annual valve check so I'll be measuring this soon.

http://img.photobucket.com/albums/v443/jcp8832/valveclearances.jpg

I've been setting exhaust valves at .004-.005" now on the 02 GS when changing shims and limiting revs to 9-9.5k rpms.  Seems to work for me.  I got my .002-.005" range idea from my 82 CB750 specs which had a 9500 rpm redline and didn't have this exhaust valve regression problem.  I think Suzuki is using too tight valve clearance specs on the GS to get the 11k rpm  redline which is totally unneccesary on an engine that peaks at 8500 rpm.

If you want to redline the GS engine after appropriate carb jet, intake, and exhaust changes to increase the power peak then check valves more often and change shims to keep exhaust valves in a narrow  .002-.003" range.

I've been thinking in inches for 76 years now so I don't intend to start thinking in mm.  You can convert where necessary.   

Pull the head and fix after you get down to a minimum shim.

[HPP8140]

gsjack, where did you find a 215 shim? I was worried because I thought the smallest was 230?

[gsJack]

Local dealer had full range of shims down to 215.  Some aftermarket shims only go down to 230 min.

[HPP8140]

Actually, let me start another thread.

Anyone looking for a project/parts bike haha.

95 GS500E 35K $500

[HPP8140]

Or anyone want to do the work for me for some cash. I'm in Northern VA.

[The Buddha]

I know of a good shop who'd do the head for 100 (and you have to supply them a valve ...) I am sorry I dont have swappers, I sold the last head I had, to Ineedanap.
Dgyver has been able to pull the head with the motor in the frame (if I recall).
Now let me also post this question ...
Is he likely to break off a chunk or the head of the valve with it burning up like it is ?

If so, fix it now.

Cool.
Buddha.

[intergalactic]

I am with gsJack. Add some more valve clearance. If your measurement method results in things on the tight side, then at .002-.003" there is little margin left. Limit the revs. Jet a little rich to reduce available oxygen in the exhaust, in doing so, you are less likely to erode the seat. Don't add oil to the gas. That lowers the octane equivalence rating. You might start pinging. A "instead of lead" additive is a possibility.



Then in the winter pull the head and put a new valve in it. Or have it done.

Edit:  Or drive it up here and I'll buy it for $500 plus train fare home on the Amtrak Acela.

Increased exhaust valve clearance allowing the valve more cooling time on the seat seems to be very effective in extending GS valve life.  I had one exhaust valve on my 97 GS down to a 215 minimum shim at 76k miles.  It started it's fast regression at about 40k miles after running at a minimum clearance for over 30k miles before that.

My 02 GS had an exhaust valve starting to receed at 30k miles after running at minumum clearance for many miles.  I increased the clearance to .005" (.012 mm approx) at about 40k miles and it still had .004" clearance at about 60k miles and now at almost 70k miles it stills idles smooth cold indicating it still has clearance 30k miles later.  It's time for my annual valve check so I'll be measuring this soon.

http://img.photobucket.com/albums/v443/jcp8832/valveclearances.jpg

I've been setting exhaust valves at .004-.005" now on the 02 GS when changing shims and limiting revs to 9-9.5k rpms.  Seems to work for me.  I got my .002-.005" range idea from my 82 CB750 specs which had a 9500 rpm redline and didn't have this exhaust valve regression problem.  I think Suzuki is using too tight valve clearance specs on the GS to get the 11k rpm  redline which is totally unneccesary on an engine that peaks at 8500 rpm.

If you want to redline the GS engine after appropriate carb jet, intake, and exhaust changes to increase the power peak then check valves more often and change shims to keep exhaust valves in a narrow  .002-.003" range.

I've been thinking in inches for 76 years now so I don't intend to start thinking in mm.  You can convert where necessary.   

Pull the head and fix after you get down to a minimum shim.

[Ry_Guy]

Dgyver has been able to pull the head with the motor in the frame (if I recall).

I've done it too. It's tedious work, but do-able. Probably a lot easier than putting a heavy new engine in as well. Your pistons and everything else is probably fine.

[HPP8140]

Well, I put in a 225 shim and am running it on the loose end with .09mm clearance. It's such a shame for 1 valve to crash the party because the engine runs strong. I know when that valve is getting tight because it takes longer to warm up until it idles without choke, otherwise, when it warms up it's fine. I also picked up 220 and 215 shims. If I take it easy I could get 10k miles or maybe 15, but what fun is that haha. It's used everyday to commute to work 26mi one way @ 80mph 7k on the tach. Guess I'll be looking to see how much a dealership will give me for it, so I can buy another one or keep my eyes open on an engine.

[HPP8140]

Are you serious on that offer? I rode it to Indy last year for MotoGp...Boston is closer 

I am with gsJack. Add some more valve clearance. If your measurement method results in things on the tight side, then at .002-.003" there is little margin left. Limit the revs. Jet a little rich to reduce available oxygen in the exhaust, in doing so, you are less likely to erode the seat. Don't add oil to the gas. That lowers the octane equivalence rating. You might start pinging. A "instead of lead" additive is a possibility.



Then in the winter pull the head and put a new valve in it. Or have it done.

Edit:  Or drive it up here and I'll buy it for $500 plus train fare home on the Amtrak Acela.