Valve clearances and feeler gauges

[DoktoroKiu]

So of the two sets of feeler gauges I have the minimum measure is 0.038 mm.  I believe my valves are tight, but I can't measure how much to get the right shims.   Do they make gauges with .03 and under, or is there just something I'm missing here?  The lowest I've found with a preliminary google search is 0.02 mm.

What would I do in the case where clearance was under the lowest gauge I can get?  Just guess?  I'm thinking about just buying several smaller sized shims and just trying those until I can get a valid measurement.

Also, my Haynes manual says to just trash the little rubber o-rings for the bolts that hold the valve cover on and get new ones.  Is this really necessary?  Mine look in good shape and I'd prefer not to wait on parts  (should have read the fine print before I started the work).

I am VERY glad that my valves are tight, though.  Hopefully my idling issues go away.

[jsyzdek]

I am VERY glad that my valves are tight, though.  Hopefully my idling issues go away.

well, I'm not sure about intake, but you really want to be on the loose side for the exhaust valves. Factory specs say 0.03-0.08, you can go as high as 0.11. If you stay on the tight side, you will keep changing the shims every few thousand miles. If you stay on the loose side, you'll be good (almost) forever. That will allow better cool down for the exhaust valves.
I'm not sure about intake, but my understanding is that you want to be in spec on that side.

Also, my Haynes manual says to just trash the little rubber o-rings for the bolts that hold the valve cover on and get new ones.  Is this really necessary?  Mine look in good shape and I'd prefer not to wait on parts  (should have read the fine print before I started the work).

If they're really in good shape - go ahead and reuse. Even if they're not in perfect shape, but good enough - you can still reuse and ride for a few days while waiting for the new ones. It's not that critical, as long as you don't mind getting dirty with it again to change for the new ones.

[gsJack]

I started checking GS500 valves with an inch size feeler gage set and have done so ever since about 20+ times already I think.  Smallest feeler was a .0015" and that was soon gone and after replacing it once and it was soon gone again (too fragile) I've only used .002" and up feelers.

When I found one less than .002" I checked to see if I could turn the bucket with my fingertip and if I could I recorded it as .001" clearance.  Doesn't really matter though, if that's an intake it's OK and if it's an exhaust it's way too tight.  Discovered on my 97 GS that an exhaust valve left at .001" clearance for many miles would soon require constant shim changes and was down to a 215 minimum shim before 80k miles with no where to go.  When my 02 GS started the same pattern I went to a .003-.005" tolerance for exhaust valves and they then held for tens of thousands of miles as I found intakes do.

I've never touched those O-rings for the cover hold down bolts for over 180k GS miles, originals went all the way, so far.  Found the cover gaskets good for about 30k miles before they started leaking.

Unless they are very tight the valves will not affect your idle after warm up.  The clearances quickly increase as the engine heats and tight valves loosen and the idle smooths out in a minute or two.  Tight exhaust valves do affect valve life greatly though.

http://img.photobucket.com/albums/v443/jcp8832/GSvalvelogs_zps9ef7236a.jpg

[jsyzdek]

So you're saying that as long as the intake valves are in spec, they should be fine?

What's your recommendation on doing the job (checking clearances): should I do it on a cold engine? or should I take it for a few mile ride, let it cool a little and then do the work?

[DoktoroKiu]

Thanks for the input, guys.  I figured the O-ring replacement policy was A$$-covering of some type.  My cover gasket looks to be in good condition, but I haven't removed it from the cover and inspected it thoroughly quite yet.

@jsyzdek:  I intended to imply that I'm glad that I found my valves to be tight, because if they were in spec it means something else is the cause of my idling/dying problems.  I fully intend to put the exhaust valves on the loose side.

@gsJack:   I'm thinking they are very tight.  The bike only had a little over 9k miles when I got it, and the guy I bought it from almost certainly didn't check them.  My guess is that the original owner before him never got around to getting them serviced at the proper interval (I think it says 5-6k miles in my Haynes).

I have only gotten approximately "normal" behavior after maybe an hour of solid riding, so maybe it took them a while to warm up.  According to my readings the tight valves lead to a loss of compression at lower RPMs, which leads to rough idling.  I also have the magical ability to adjust the idle knob significantly without (immediately) affecting the idle speed.  The behavior does change when I adjust it, but I'll be damned if there's a pattern to it.  I've also read that tight exhaust valves make it very difficult to set idle speed.

On the setting I have now the idle varies between 900 and 1300 RPM.  The thing is, it stays rock solid at whatever value it chooses at a given stop.  Sometimes it idles fine, sometimes it wont stay above 1000 without some throttle.  Even with it set to a higher idle it will die when I'm coming to a stop if I roll off the throttle too quickly (at a very normal pace).  I don't believe it is dropping RPMs too quickly, it's just once it gets down to idle speed it keeps dropping and dies.

At any rate I'm probably going to be looking at the carbs after this, but I'm 90% certain the valves are the majority of my problem.

[gsJack]

jsyzdek, I never touched the intakes on my 97 and it had same shims it came new with at 80k miles when it was totaled and replaced by the 02.  Changed an intake shim once on my 02 and changed it back again next time and it too now has the same intake shims at 100k miles that it came with.

Always do valve checks cold, I do mine after they sit overnight.

http://img.photobucket.com/albums/v443/jcp8832/GSvalvelogs_zps9ef7236a.jpg

[jsyzdek]

Thx! 

[gsJack]

Mmmm DoktoroKiu, you'll know soon now how tight or loose your valve clearances are but I doubt they are the cause of your idle problem. Shouldn't take an hour for your GS or any other GS to warm up even when it's below 32F out.  If you have the valve cover off it would only take a couple minutes to check if your 4 buckets can be turned with your finger tip with the cam lob turned away from the bucket/shim indicating some clearance.

I was curious about how much the valve clearances actually do increase as the engine warms so about 25-30 years ago with my CB750K which also had shim over bucket valve adjustment like the GS has I took a ride to warm it and headed home and quickly pulled valve cover and checked some of them.  Found valves that had .002-.005" clearance cold had at least .015" clearance hot.  That .002-.005" Honda shim over bucket valve spec played a part in my decision to set my GS exhaust valves to .003-.005" and is noted as reference at the bottom of my valve check log linked above.

[DoktoroKiu]

Mmmm DoktoroKiu, you'll know soon now how tight or loose your valve clearances are but I doubt they are the cause of your idle problem. Shouldn't take an hour for your GS or any other GS to warm up even when it's below 32F out.  If you have the valve cover off it would only take a couple minutes to check if your 4 buckets can be turned with your finger tip with the cam lob turned away from the bucket/shim indicating some clearance.

I was curious about how much the valve clearances actually do increase as the engine warms so about 25-30 years ago with my CB750K which also had shim over bucket valve adjustment like the GS has I took a ride to warm it and headed home and quickly pulled valve cover and checked some of them.  Found valves that had .002-.005" clearance cold had at least .015" clearance hot.  That .002-.005" Honda shim over bucket valve spec played a part in my decision to set my GS exhaust valves to .003-.005" and is noted as reference at the bottom of my valve check log linked above.

Are the buckets the cylindrical part just under the shims?  So I would remove the shims and attempt to rotate the buckets when the cam lobes are not facing them?  What does this test for?

I'm wondering if my symptoms are due to a bad idle setting as a result of the PO messing with it trying to compensate for the idling issues caused by tight valves.  I suppose an hour to warm up isn't 100% accurate, as it never "warms up" in that it still has trouble idling.  I just meant to say it runs much better after 30-60 minutes of solid riding (maybe it's me that's warmed up...).  It could also very well be carb-related, but I've seen more than one reference to tight exhaust valves causing problematic idling.  Actually, in my original thread here about idling itstartswithken said he suffered from similar issues and it ended up being tight exhaust valves.

Even though heat opens the clearances up I'd be afraid to try and draw any conclusions from these measurements.  I would imagine that these effects would have already been taken into consideration when they made the recommended clearances.  I'm no mechanical engineer, but I'd wager that valve clearance might be used as a tool to indirectly measure something else (kind of like torque is used to indirectly measure the strain on a bolt shank, force on a gasket, etc.).  Perhaps valves that have .03-.08mm clearance cold have the proper clearance when hot, or the proper clearance + timing combination.

My intuition would tell me that if there's ANY clearance at all the valves should always be able to fully seat, but clearly that is not the case if under-spec clearances can still cause valves to fail to seat properly.  And the timing should definitely be affected by more/less gap.

[gsJack]

Yes the buckets are the cylindrical parts just under the shims that hold the shims. You should have clearance between the shim and the heel of the cam lobe with the lobe turned away from the bucket/shim with the shim in place in the bucket (aka tappet).  The clearance is to make sure the valve is closerd tight when it's supposed to be closed and doesn't leak compression losing power.  Clearance is necessary with mechanical arrangements like our GSs have, modern cars and a few bikes have hydraulic adjusters now that eliminate the clearances without holding the valves open when they are supposed to be closed.  If you can't turn the bucket with the lobe away then you have a tight valve or possibly a tight bucket which is another problem.

While some clearance is necessary it's desirable to have a minimum amount so valve lift (amount open) is maximum and also to minimize tappet noise.  At the same time the exhaust valves run very hot and require some cooling and that is provided by heat transfer to the valve seat in the head when the valve is closed.  Too little clearance keeps valves open longer reducing cooling seat time for the exhaust valves. Exhaust valves run at the minimum .001" (.03mm) Suzuki spec for a long time do not give enough seat time for cooling and the too hot running valves begin to recede into the seats requiring constant shim changes to maintain enough clearance for valve seal and even burnt valves in extreme cases.  The increased exhaust valve clearances are working out well for many here including myself.

Get you valves checked and adjusted and then worry about your idle problem if you still have it.  Tight  valves will cause a rough idle when cold but they open up so fast as they heat that it's not a problem when hot unless they are really bad.

[DoktoroKiu]

Yes the buckets are the cylindrical parts just under the shims that hold the shims. You should have clearance between the shim and the heel of the cam lobe with the lobe turned away from the bucket/shim with the shim in place in the bucket (aka tappet).  The clearance is to make sure the valve is closerd tight when it's supposed to be closed and doesn't leak compression losing power.  Clearance is necessary with mechanical arrangements like our GSs have, modern cars and a few bikes have hydraulic adjusters now that eliminate the clearances without holding the valves open when they are supposed to be closed.  If you can't turn the bucket with the lobe away then you have a tight valve or possibly a tight bucket which is another problem.

While some clearance is necessary it's desirable to have a minimum amount so valve lift (amount open) is maximum and also to minimize tappet noise.  At the same time the exhaust valves run very hot and require some cooling and that is provided by heat transfer to the valve seat in the head when the valve is closed.  Too little clearance keeps valves open longer reducing cooling seat time for the exhaust valves. Exhaust valves run at the minimum .001" (.03mm) Suzuki spec for a long time do not give enough seat time for cooling and the too hot running valves begin to recede into the seats requiring constant shim changes to maintain enough clearance for valve seal and even burnt valves in extreme cases.  The increased exhaust valve clearances are working out well for many here including myself.

Get you valves checked and adjusted and then worry about your idle problem if you still have it.  Tight  valves will cause a rough idle when cold but they open up so fast as they heat that it's not a problem when hot unless they are really bad.

Oh, that makes sense.  I'll try that before I take them out tonight.  I think I'm just going to go and grab a much-shorter shim from the local shop so I can get measurable clearances.  I should have taken one out last night and recorded the value, as now I'm basically limited to the turn test for tonight until I can get the shim from the shop.

Might see what else I can cross off the regular maintenance list while I wait.  I also noticed a few issues that need addressing when I was working my way to the valve cover, notably that my battery vent tube is bad and there's some corrosion in that area now.  My right spark plug also has some light corrosion around it, and everything else could use some cleaning.

That's interesting about the hydraulic adjusters, as I've been wondering why I've never heard of valve clearances being a regular part of car maintenance.

I'll definitely shoot for the .03-.05" setting you mentioned, and hopefully that will clear the issue up.  I guess I'll look forward to some more one-on-one wrenching time with her, and then I'll hopefully be pleasantly surprised if I don't need to.

[yamahonkawazuki]

had a set of gauges .001" to .025" ( precision brand)  would offer these but it appears theyd not serve your needs at all.

[yamahonkawazuki]

actually these might work after all
http://www.amazon.com/Precision-Brand-Thickness-Poc-Kit-Assortment/dp/B007IVPCSY

[prmas]

These are the ones I bought and use successfully. They are very cheap but seem to be good quality. 

http://www.ebay.com.au/itm/251259072299?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Macka

[DoktoroKiu]

Thanks for the feeler gauge suggestions, guys.  I will order one next time I'm on a buying spree from Amazon.  I figure I'll set the clearances to the middle of the range on intakes, so I'll be able to use what I have this time.

Turns out I have all factory shims (272 intakes and 278 exhaust), so I was right that they were never changed, and possibly right that they were never checked.  All of them did have some clearance, as I was able to spin the bucket.  Those durn shims are hard as heck to get out of there until you learn the trick (small diameter magnetic extender).  It's amazing that, no matter how many tools you have, you are always missing (or can't find) the one you need on your current project...

None of the shops in town have (or know they have) the 29.5mm diameter shims, so I had to order some.  I got four 270s and two 265s just in case.  I figure I can go all 270 to start with, and if I end up needing a little more on the exhaust the 272s will be good enough.  Priority mail from Indianapolis shouldn't be more than 2 days.

In the meantime I have carbs to clean and I might clean up some rust on the exhaust.  The '09 models have every emissions control device known to man, and some that aren't (at least to me).

[BockinBboy]

Sorry I didn't see this sooner to comment... But to comment toward your issue with 'too large' of feeler gauges for your clearances.  That's really not a bad thing.  I've seen many folks new to measuring clearances (not necessarily GS clearance, but gaps in general) actually force the thinner gauges into spaces that are actually too tight for them to fit.  They are so small and flimsy you can get them to slide into spaces they shouldn't be able to, if that makes sense.  So you end up thinking your gap is larger than it is.  For these cases, its best to get what folks call a 'test shim'. All that means is a shim several sizes smaller than what is in there.  So if yours is a 278 and you can't measure it with your smallest feeler gauge, or seems tight with the feeler gauge in the gap... then you swap the 278 shim with a 250 (or so) and measure your clearance with that, and go from there. 

Always measure each shim you take out, and each shim you put in with calipers to confirm they are the sizes they say they are.. and check clearance before you take out, and after you replace - cross check that with the math you used to figure out the correct sized shim to put in... make sure everything adds up!

- Bboy

[DoktoroKiu]

Sorry I didn't see this sooner to comment... But to comment toward your issue with 'too large' of feeler gauges for your clearances.  That's really not a bad thing.  I've seen many folks new to measuring clearances (not necessarily GS clearance, but gaps in general) actually force the thinner gauges into spaces that are actually too tight for them to fit.  They are so small and flimsy you can get them to slide into spaces they shouldn't be able to, if that makes sense.  So you end up thinking your gap is larger than it is.  For these cases, its best to get what folks call a 'test shim'. All that means is a shim several sizes smaller than what is in there.  So if yours is a 278 and you can't measure it with your smallest feeler gauge, or seems tight with the feeler gauge in the gap... then you swap the 278 shim with a 250 (or so) and measure your clearance with that, and go from there. 

Always measure each shim you take out, and each shim you put in with calipers to confirm they are the sizes they say they are.. and check clearance before you take out, and after you replace - cross check that with the math you used to figure out the correct sized shim to put in... make sure everything adds up!

- Bboy

I did measure the shims with a micrometer, and they checked out.  I figured that with the small gauges if I can't get them in there without forcing them then it's not a fit.  I should have thought about getting a test shim, though.  Maybe next time.

[cWj]

THREAD RESURRECTION!!!!!

Valve job tidbits:

do the number on the shims correspond to metric or imperial?

is the normal course for valves to tighten or loosen?

[gsJack]

The size numbers on oem shims are metric, my opinion on non oem shims is don't touch them.

My shim changes were all to smaller shims on exhaust valves and no changes required on intake shims for 180,000 GS500 miles.

If you're getting shim/cam wear resulting in larger clearances stop using Walmart brand cheapest oil.   

http://img.photobucket.com/albums/v443/jcp8832/GSvalvelogs_zps55f27f5e.jpg

[The_Paragon]

My shim changes were all to smaller shims on exhaust valves and no changes required on intake shims for 180,000 GS500 miles.

I'll second that notion!!!!

If you're getting shim/cam wear resulting in larger clearances stop using Walmart brand cheapest oil.   

On my newer Yamaha 600's (R6, Fz6, FZ6r) Its actually a standard normal for exhaust valve clearance to wide. The valve face and valve seat are of such good quality that they wear very minimally. Leaving other componants to show the wear, like the top of the bucket possibly. And I mean very very little wear! 1st valve check is reccomended at 24,000 miles and most people dont adjust anything untill the 50,000 mile mark.