exhaust valves tightening prematurely?

[termlifed]

When I got my bike I was having trouble stalling when decelerating to a stop and trouble starting back up afterward. After ruling out carb issues I checked my valves. My exhaust valves had little to no clearance as the buckets wouldn't turn. I dropped the shim size .10mm from 2.70mm to 2.60mm on both exhaust valves and the bike ran like a champ. 2000 miles later I'm experiencing the same symptoms I had before with tight valves. I have been running the bike fairly hard with shifts at 10k or so but 2k miles is only half of the suggested valve check period and seems like a really short time for the valves to tighten up again. I changed spark plugs yesterday and will check the valves tomorrow. I'm not sure if I need to give even more clearance than I gave last time or if something more is wrong beyond valve clearance. Any ideas? Thanks

[Funderb]

are you checking the valves dead cold, as recommended?

and by "fairly hard... shifting at 10k" are you thrashing it everywhere at WOT? You'll definitely wear things out faster that way, but pretty much every bike will vary depending on how its taken care of.

BTW
if your mix is hot, or the engine is running hot or low oil, your valves, especially the exhaust will stretch more quickly.
Running it hard all the time on the stock jetting may be a problem, but burning1 never seemed to have a problem with it... hmm

[Juan1]

What was your exhaust valve clearance with 2.60s?  The wise GS Jack noted that the exhaust valve clearance will reduce more quickly if you initially set them to the tighter side of spec.  He personally set his to .08-.13mm and had a long engine life on his second GS. Others here have gone to that exhaust valve spec without any problems.

I just checked my new-to-me GS500 clearances and found the exhaust valves to need 250 and 255 shims in order to achieve .08-.13 clearances.  Could it be the case that the 260 shims were still on the tight side?

[termlifed]

are you checking the valves dead cold, as recommended?

and by "fairly hard... shifting at 10k" are you thrashing it everywhere at WOT? You'll definitely wear things out faster that way, but pretty much every bike will vary depending on how its taken care of.

BTW
if your mix is hot, or the engine is running hot or low oil, your valves, especially the exhaust will stretch more quickly.
Running it hard all the time on the stock jetting may be a problem, but burning1 never seemed to have a problem with it... hmm

Yup, I checked multiple times from dead cold using the timing marks as I waited for my shims to come in. I do tend to ride at WOT regularly mixed with some stop and go traffic so maybe it was running a bit hot.I keep track of oil level regularly and I did notice some oil burning. I just switched from the regular 10w-40 motorcycle oil to 15w-40 Rotella T, which I hope will keep running temps down and keep oil from burning up. 

What was your exhaust valve clearance with 2.60s?  The wise GS Jack noted that the exhaust valve clearance will reduce more quickly if you initially set them to the tighter side of spec.  He personally set his to .08-.13mm and had a long engine life on his second GS. Others here have gone to that exhaust valve spec without any problems.

I just checked my new-to-me GS500 clearances and found the exhaust valves to need 250 and 255 shims in order to achieve .08-.13 clearances.  Could it be the case that the 260 shims were still on the tight side?

At  260mm my feeler gauge was showing limited clearance(cant remember exact clearance) but I chalked it up to the way it was sitting in the oil or something. But going down from 2.70mm to 2.60mm would put me at .10mm clearance at the minimum by way of basic math. Maybe I have to give her more than that, like .13-.15mm. I was worried that the wider clearances in addition to riding in the upper rpm range would cause valve shim float(correct terminology?). I'll open her up and see where the clearances are at today as in 2kmiles they should have settled into accurately readable position.

[gsJack]

Time for a cold compression test before changing any more shims.  If you don't have a guage available at least give it a simple thumb over the hole and crank type test that will tell you if you have any cold compression, no pop is a bad, a loud pop is good.

You mentioned tight buckets in your first post above but it's not clear whether you meant too tight of a fit of the buckets in the head or just too tight from lack of any valve clearance.  If you have tight exhaust valves again after your .10 mm shim change last time resulted in it "running like a champ" then 2k is too few miles for tight valves again, should go at least 5-10k miles between valve checks and shim changes.  I've found that with the increased .08-.13 mm exhaust valves clearances my 02 GS is going tens of thousands of miles between shim changes. 

I've had a too tight valve as well as a tight bucket on my 97 and 02 GSs and in both cases when it started up on one cylinder running rough it smoothed out in a minute as the engine heated and the 2nd cylinder came in a minute after starting.  Tight buckets loosen and valve clearance increases as the engine heats up.

[bombsquad83]

I thought clearances decreased as the engine warms up?  Makes sense that the tight bucket would loosen though.  What do you do about a tight bucket?

Also to the OP.  Did you measure the clearance after you went to the 2.60mm? 

[gsJack]

I thought clearances decreased as the engine warms up?  Makes sense that the tight bucket would loosen though.  What do you do about a tight bucket?

Also to the OP.  Did you measure the clearance after you went to the 2.60mm?

Valve clearances increase on overhead cam engines with aluminum heads.  Aluminum expands faster with heat than steel and the expanding head lifts the camshaft away from the slower expanding steel valves.

Since my tight bucket loosened in a minute or less after starting and was good for the day after that I decided to let it go for a while to see if it would wear in and loosen up in time. Bought bike used and discovered the tight bucket at first valve check at about 10k miles and one very cold morning morning at 21k miles it stopped with a bang while cranking to start and engine was locked up with a broken exhaust valve.  I then pulled the head and fixed it like I should have when first discovered.  There have been quite a few reporting tight buckets here since then and the only way to fix it right is to pull the head and replace the bucket with a smaller one unless you can manage to get the bucket out by only pulling the camshaft out of the way.  My bucket was so tight that when I managed to get a screwdriver into the notch and hit it hard with a hammer it wouldn't budge.  After I pulled the head I drove the valve shaft and bucket up and out with a long punch from the inside and it drove hard all the way.  It's surprising how fast they heat and loosen when the engine is started up.

[noiseguy]

Generous clearances are better.

One thing on your bike. If the valves were tight to begin with, it's a good idea to recheck a few hundred miles after to see how they're doing. Sometimes carbon has developed under the exhaust valve and gets bashed off the valve/seat immediately after the shim change. Then you're back to tight again... sounds like it's time to re-adjust.

[termlifed]

Time for a cold compression test before changing any more shims.  If you don't have a guage available at least give it a simple thumb over the hole and crank type test that will tell you if you have any cold compression, no pop is a bad, a loud pop is good.

You mentioned tight buckets in your first post above but it's not clear whether you meant too tight of a fit of the buckets in the head or just too tight from lack of any valve clearance.  If you have tight exhaust valves again after your .10 mm shim change last time resulted in it "running like a champ" then 2k is too few miles for tight valves again, should go at least 5-10k miles between valve checks and shim changes.  I've found that with the increased .08-.13 mm exhaust valves clearances my 02 GS is going tens of thousands of miles between shim changes. 

I've had a too tight valve as well as a tight bucket on my 97 and 02 GSs and in both cases when it started up on one cylinder running rough it smoothed out in a minute as the engine heated and the 2nd cylinder came in a minute after starting.  Tight buckets loosen and valve clearance increases as the engine heats up.

The last time I did the valves the bucket would spin without the shims in but was stuck with them installed. Today I had to ride the bike so I havent gotten around checking the valves as of yet. I did however check the compression and it was fine on both sides. I also found out that I was getting no spark on the right hand plug.  Since the plugs are brand new I assume that it's either the coil or the signal generator causing the lack of spark.  Could this cause of the idle issues or am I chasing an unrelated issue. Thanks

[gsJack]

Good the buckets will spin free without the shims but if they are tight after shims are put back in and with the cam lobes turned away from the shims then they are still too tight needing yet smaller shims.  If they were tight with original shims but had some clearance with your .10 mm smaller exhaust shims put in last time they must have been about right then.  If you had cold compression you had some clearance and bike should run ok for now but too little clearance will shorten exhaust valve life over the long run, over many miles.

It's very rare but one member put in new plugs recently and one of them turned out to be bad, think it was adidas.  Switching plugs could show that or if the same side still isn't firing it could be a pickup or coil problem but be sure it's not just a loose coil wire first, I had/have one on the 02.  The plug wires are tight in the coils and can't be turned, if one is free to turn it could be missfiring and causing idle issues as well as running issues.  The plug wires screw into the coils and are bonded in place there so if you have a loose one just tighten it up and see if that helps, it's a right hand thread.  I just snip a bit off the wire and put a big dab of dielectric grease on the wire and screw it in tight and it's good for another year, best fix would be new coil and wire assembly. 

[burning1]

I ran stock jetting on my race bike. I did notice a little glazing on the spark plugs, but never had an issue with it. I didn't have any engine mods.

I recommend opening the clearance on the intake and exhaust by 1 shim size larger than the stock recommendation. IIRC, stock clearance is .03mm-.08mm on the exhaust... I followed the advance I'd seen on the forum, and went to .12, .09 or so. Clearance was still good after 30 days of race use. Never had an issue, even running the bike at red-line.

The GS500 burns oil. Running a low volatility oil, such as Amsoil MCV will help a lot. Running a thicker oil (20w50) will also help, though I wouldn't recommend it unless you live in a warm area. Generally, Group IV synthetics (PAO base stocks, such Amsoil) are really stable. Group II conventional oils are volatile. Group V ester oils are highly volitile (Motul 300V, Silkoline)

Check your oil regularly. When oil levels get low, you tend to spin the left big-end rod bearing. If you keep running the engine, you ruin the crank, cases, etc.

[termlifed]

Ok, so I opened her up today and the exhaust valves had less than .04mm clearance (my smallest gauge). The right exhaust bucket, even with the shim removed, was extremely tight . It would only spin if I put an excessive amount of force into it. The left exhaust bucket was not as tight but would not spin freely like the intakes. Given the situation should I drop them down another .10mm or am I looking at something more involved. I'm thinking that something is not right if I'm having this problem only 2k miles after the last adjustment.

I also checked over my spark plugs,coils,etc and it turns out I  do have spark on both sides, so im pretty sure its just my valves giving me trouble

[termlifed]

Threw in a 2.55 and still cant get my smallest gauge to register. I'm going to order a couple of 2.4 and 2.35mm shims and go see how that works out. If that doesn't do it then.....

[gsJack]

My tight exhaust bucket was really tight, I could put a screwdriver in the notch and hit it hard with a light hammer and it would not budge the bucket.  Could not turn it at all with a cold engine yet when I started it up and the head began to heat that bucket would free up in a minute and the engine would smooth out as that cylinder came in and it would run "like a champ" the rest of the day.  Came from the factory that way and ran good for 21k miles before I cranked it one very cold morning and it stuck even tighter and broke the valve.  If you can turn the buckets even though a bit tight you should be running good as new as soon as the engine begins to heat if you have any clearance at all cold and nothing else is wrong.  Running the valves on the tight side as long as they have some minimum cold clearance will shortened the valve life over the long run but have no immediate effect beyond startup.

Good you ordered those smaller shims, put a couple in and measure the clearance and go from there to figure shim size needed.  Make sure you turn the engine over clockwise with the 19 mm hex on the right end of the crank and turn it a few complete turns to squeeze out any oil trapped under the shim that might give a false reading before measuring gap after changing shims.

As long as you have cold compression and you don't have a really excessively large amount of valve clearace engine should run good unless something else is wrong.  Just don't ride it with your heavy throttle hand with way too much clearance or you risk throwing a shim.  Burning 1 seems to be doing OK at track speeds with the .08-.13mm valve clearance settings, hope you're not exceeding track speeds on the street.   

[termlifed]

Hey guys quick question, I finally have clearance on my exhaust valves with the 2.40mm shims. . Here's the catch, the left exhaust is between .13-.15 with the right being  between .15-.17. I know its ok to run them a little high but is this too high or can I run this without problems. Also my engine was only down for about 4-5 hours so I'm not sure how much that skewed my readings. Thanks

[Bluesmudge]

.15 - .17 is too much clearance. I think you should go up one shim size.

[bombsquad83]

I've read that you should let it cool all overnight.  If its room temperature to the touch I would think it would be ok though.

[twinrat]

you are only a couple of thou up .it will only be a little more rattly and probably wont even notice it ..If you had clearance greater than say half the depth of the rim of the seat where the shim sits i would then be worried about the shim jumping out .Ihave never seen or know of any one who has had this happen. As you say your clearance keeps reducing  over a short period this will allow you to sort your problem ,which could be valve elongation from over reving or valve seat pocketing .use it dont be put off .

[gsJack]

If you wind it up to rpm's where the valves actually float you can possibly have a nice big gap in there for a shim to slip out but ridden reasonably your current gaps of approx .15 mm would not be likely to cause any problem beyond noisy tappets.  I started suggesting to others the setting of exhaust valves on the GSs a bit wider than spec after seeing one of mine that was run on the tight side of the Suzi spec get down to a minimum 215 shim before 80k miles and the other exhaust valve that had the max Suzi spec hold the same mostly for the life of the engine like intake valves do.

I suggested setting them at .08-.13 mm, to the max spec and up a bit.  That was all that was needed to give a nice long life to the GS exhaust valves so no need to go further.  But I did notice it took a of couple shim changes for the tighter exhaust valve on my 2nd GS to settle down and then go tens of thousands of miles without further changes, see my log.

If that was my bike termlifed, I'd run it as is for a few thousand miles to see where those approx .15 mm gaps go, could be they'll close up a bit before settling down.  BUT, I'd limit it to a 9-9.5k rpm redline until the next valve check.  If you can't remember that at all times stick a piece of masking tape on your tach at 9.5 as a reminder.   

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