I am trying to sort out the valve clearances on the head of my 91 gs500, which I just had redone after bending a valve at the track. When I got the top end back together there was no clearance on any of the valves. No surprise I figured as everything had been apart and back together while the head was redone, new springs and all that. I ordered the 215 shim (which I think is the thinnest) as a test shim, thinking this would give me a baseline to find the correct shim thicknesses. Guess again. Still no clearance on the left side exhaust valve. WTF is going on? I am completely bemused. I havent checked to see if the thin shim gives me clearance on the other three valves yet as I was too pissed off and the friggin valve shim tool kept slipping (as they do) - figured I'd call it a night and try again when my temper has a longer fuse - not sure the neighbor would appreciate a GS500 sailing over his fence. Anyone have any insight? Is this an issue with the shim needing to bed in before I can get a reliable measurement? The buckets do spin, but then they span when the original shim was in there too (something like a 290), so I am not sure what thats really telling me either. I'm reluctant to start the bike with such little clearance in case of damaging the valves (again) . Any help greatly appreciated.
Quote from: IL_Rider on September 12, 2006, 06:33:37 PM
I am trying to sort out the valve clearances on the head of my 91 gs500, which I just had redone after bending a valve at the track. When I got the top end back together there was no clearance on any of the valves. No surprise I figured as everything had been apart and back together while the head was redone, new springs and all that. I ordered the 215 shim (which I think is the thinnest) as a test shim, thinking this would give me a baseline to find the correct shim thicknesses. Guess again. Still no clearance on the left side exhaust valve. WTF is going on? I am completely bemused. I havent checked to see if the thin shim gives me clearance on the other three valves yet as I was too pissed off and the friggin valve shim tool kept slipping (as they do) - figured I'd call it a night and try again when my temper has a longer fuse - not sure the neighbor would appreciate a GS500 sailing over his fence. Anyone have any insight? Is this an issue with the shim needing to bed in before I can get a reliable measurement? The buckets do spin, but then they span when the original shim was in there too (something like a 290), so I am not sure what thats really telling me either. I'm reluctant to start the bike with such little clearance in case of damaging the valves (again) . Any help greatly appreciated.
Have you watched Kerry's Valve video? Do a search on it. It's a 1 hour video on how to do a full valve inspection. Make sure you are wiping the feeler gauges clean just before you insert the feeler in between the shim and the cam. Also they must be fully seated before taking the clearance. Pull off the generator cover on the right side of the bike and turn the 19mm bolt clockwise to turn the engine. This is the safest way to turn your engine when the bike is off. Turn the engine several times to sit the shim. Then take the clearance.
My manual says that when you replace a shim you're supposed to turn the engine over once before checking the clearance, to push out any oil on the shim. If you have the smallest shim and still have no clearance, you can sand it down untill it works. Just try to keep it flat while sanding, and finish it up with a real fine grit. Hopefully this should work.
:cheers:
Quote from: ducati_nolan on September 12, 2006, 10:15:08 PM
My manual says that when you replace a shim you're supposed to turn the engine over once before checking the clearance, to push out any oil on the shim. If you have the smallest shim and still have no clearance, you can sand it down untill it works. Just try to keep it flat while sanding, and finish it up with a real fine grit. Hopefully this should work.
:cheers:
No way, that's asking for problems unless you have an ultra-precise surface grinder ($10,000 +) and know the proper techniques to avoid weakening the shim.
If the bucket turns freely with the cams installed then you have at least
some clearance. Are you sure you're using the right feeler gauge? Make sure you're testing with the .04 mm (not inch) blade, that it's clean, and that there isn't another blade stuck to it by mistake.
Lets see. Yes, I am 100% sure I'm using the right feeler gauge. I have watched the video on the valve job. I did give the engine a few turns manually to get the valve shim seated, just doesnt get me the clearance. I guess the next step is to use a washer thats even thinner and work out what the actual clearance is. I suppose I could have a set of shims thinned at a machine shop to give me the clearances. Its an odd problem for sure.
Hi there,
I think the valves are trying to tell you that you need a valve job on this cylinder head.
You didn't mention how many miles are on the bike, but it sounds as though the valves have worn deeply into the valve seats, which is why you can't get adequate valve adjustment clearance.
Have you done an accurate compression test on the engine?
If you have been racing the bike, wear is accelerated and such problems can occur.
Don't use washers to try to adjust the valves! That will lead to disaster when they are spit out by the cam lobes and tossed around the inside of your engine.
Evaluate and fix this right and start with looking at the head and at a valve job.
Good luck.
yours,
Todd
http://gstwins.com/gsboard/index.php?topic=30125.msg327539#msg327539
As stated in the orignal post, I have just had the head reworked so that shouldnt be the issue. The point of using the washer was not to use it as a permanent shim but to simply use it to gauge the clearance in order to figure out what hypothetical shim thickness I would need in order to get the correct valve clearance...
Quote from: IL_Rider on September 13, 2006, 08:04:11 AM
As stated in the orignal post, I have just had the head reworked so that shouldnt be the issue. The point of using the washer was not to use it as a permanent shim but to simply use it to gauge the clearance in order to figure out what hypothetical shim thickness I would need in order to get the correct valve clearance...
OK, I used to overhaul auto engines many decades ago and common practice was to grind the valve faces and also to grind the valve seats to restore finish. These processes would considerably reduce valve shim clearance by causing the valve stems to stick up out of the head further.
One possible fix would be grinding down shims to get proper clearance, if done it should be by a machine shop and all the grinding done on one side of the case hardened shims with the ground side inserted down so cam shaft wear is still on a hardened surface. This might not be good for an engine used for racing or frequently run at very high rpm since the possibility of throwing a shim would be greatly increased.
Years ago we adjusted the valves on the old flat head Ford V-8 by grinding off the ends of the valve stems, no screw or shim adjustment was provided. This would require dissassembly of your head to do properly but might be a way to salvage the head and get valves into proper adjustment with standard thickness shims. :dunno_white:
Quote from: IL_Rider on September 12, 2006, 10:42:42 PM
Lets see. Yes, I am 100% sure I'm using the right feeler gauge. I have watched the video on the valve job. I did give the engine a few turns manually to get the valve shim seated, just doesnt get me the clearance. I guess the next step is to use a washer thats even thinner and work out what the actual clearance is. I suppose I could have a set of shims thinned at a machine shop to give me the clearances. Its an odd problem for sure.
Yea, I agree with GSJack in that the shop probably took off too much material when they recut the seats. It's still strange that the bucket rotates freely even with the larger shim; usually if there is zero clearance the force of the cam lobe bearing down on the shim prevents you from easily turning the bucket.
Many talk about getting a min thickness shim for measuring purposes when no clearance is there to measure or maybe using a washer there. A common set of feeler guages on a single pivot pin are about 3/8" or so thick. Why not just remove the shim with the cam lobe pointed away and with a stack of feeler guages chosen till they fit properly between the bottom of the bucket recess and the heel of the cam, check to see where you are at? I've measured large gaps this way many times with an assortment of feeler gage blades stacked together using the thinner more flexible ones.
Many times the gap is too small to measure with standard feeler gauges although there is a bit of gap and the bucket can be rotated with the fingertip. I've let them go this way a few times when I didn't have a new shim handy. Remember the clearance gaps increase rapidly as the engines warms up and there will be plenty of gap on the hot engine if there is any at all with the cold engine.
Thanks for all the help. I guess my main concern/confusion, is that I was able to rotate the bucket with both the 290 and the 215 shims in there and yet I cant measure any clearance with the 215 in place. It seems like the 290 should have been WAY too tight to rotate the bucket if its rotating with a 215 with no clearance. Anyway, this engine has been raced and it sounds like the seats have either been worn down or ground down too far by the guy that did the head work, or most likely a combo of both, which is whats giving me the current clearance issue. The idea of sticking in the stacked feeler gauges is a good one and since I have a micrometer it would be quick to just figure out the right fit and then measure the stack of gauges. My frustration with the bike is much better today, so i'll have another go at it tonight and let you know what comes up (needless to say this is the end of a long line of problems/fixes which have gradually been uncovered while taking the bike apart to fix the bent valve - valve clearances dont normally do this to me!!)
Just a quick update. I checked the clearances on the intake valves and managed to adjust these to spec (one required the 215 shim and the other a 260 to get them sorted). Neither exhaust valve will give a clearance with the 215 shim. I used a quarter, which appears to be roughly 0.60" (of course its not smooth etc etc) to get a rough idea of the actual space between the exhuast valve and the cam lobe. It looks to be roughly 0.605" since i managed to get a 0.005" feeler gauge in there. Thats 1.53mm (plus or minus a small fraction for the indentations on the quarter). Of course I can repeat this more exactly with a smooth washer or whatever, but this seems super tight. That means that something like a 150 shim would be needed to get the clearances right. I guess I'll repeat tomorrow and get an accurate measurement and then head off to the machine shop to get two shims thinned down.
Quote from: IL_Rider on September 13, 2006, 07:17:09 PM
Just a quick update. I checked the clearances on the intake valves and managed to adjust these to spec (one required the 215 shim and the other a 260 to get them sorted). Neither exhaust valve will give a clearance with the 215 shim. I used a quarter, which appears to be roughly 0.60" (of course its not smooth etc etc) to get a rough idea of the actual space between the exhuast valve and the cam lobe. It looks to be roughly 0.605" since i managed to get a 0.005" feeler gauge in there. Thats 1.53mm (plus or minus a small fraction for the indentations on the quarter). Of course I can repeat this more exactly with a smooth washer or whatever, but this seems super tight. That means that something like a 150 shim would be needed to get the clearances right. I guess I'll repeat tomorrow and get an accurate measurement and then head off to the machine shop to get two shims thinned down.
I could be wrong but if you need a 150 shim something is probably wrong. :dunno_white:
beats the heck out of me - its not like there are a bunch of complicated things going on in the head really - i mean, u measure the gap and the clearance u need is what u need. I dont see any way around it. Maybe once the new head beds in the clearances will open up a little, but I'd be kinda surprised...
Did they replace the exhaust valves when you had the head worked on? If so, is it possible they used the wrong ones?
as jack stated
ya gunna have to tip the valves
Quote from: IL_Rider on September 13, 2006, 07:17:09 PM
I used a quarter, which appears to be roughly 0.60" (of course its not smooth etc etc) to get a rough idea of the actual space between the exhuast valve and the cam lobe. It looks to be roughly 0.605" since i managed to get a 0.005" feeler gauge in there. Thats 1.53mm...............................means that something like a 150 shim would be needed to get the clearances right. I guess I'll repeat tomorrow and get an accurate measurement and then head off to the machine shop to get two shims thinned down.
Just typos I'd guess, but I measured a couple quarters and they were .060-.061" thick. If you got a .005" feeler in there with a quarter then there must be approx .065" gap between the cam lobe heel and the bottom of the recess in the bucket. Not between the cam and valve.
.065 x 25.4mm/inch = 1.65 mm gap.
you need .001-.003" clearance so that would be about .063" shim desired for proper clearance or a .063 x 25.4 = 1.6mm shim.
The standard minimum shim is a 215 = 2.15 mm or about .085"
On my well worn 97 GS I was down to a 215 shim on one exhaust valve at 80k miles and was considering a shim ground just a little below the 215 for the next adjustment but the bike was totalled and replaced with my current 02 so I never tried it. I would be a bit concerned about throwing shims at high rpm's with a shim ground to 1.6 mm. :dunno_white: You gotta decide on that one. :)
I'd look into grinding off the valve stems to make it right.
Actually, I guess 0.6" is a bit thick for a quarter! HOw much of a hassle is grinding the valve stems - professional job?
Jack, Kenny?
Hate to dissagre but is tipping a good idea? It would solve the immediate problem agreed but at the same time I think it could be a compromise to overall reliability. My concern would be that the outer case hardened layer would be removed from the end of the valve stem and once thats gone the hammer effect of the cam would dramaticaly shorten the life of the valve. Older valves were chrome plated and you could loose up to about 0.010" without any serious risks, but the hardened layer on valves made from modern steels can be as less as 5 microns and there are about 25 of them per 0.001". The fact that the gap has reduced by such an amount suggests to me that serious valve-seat regression has occured for some reason as suggested earlier by Trw. If reliability is a serious issue to IL Rider it might be better to consider having the seat-inserts bored out and replaced by an engine recon` firm. Surface-grinding shims could have the same effect and remove the case hardening.
Respectfully :thumb:
maybe its cheaper just to buy a 'new' head and transfer all the hardware over.. Anyone happen to know of a place in Los Angeles where I could get new valve seats done? It seems that everyone agrees that this is the underlying issue causing the lack of valve clearance. Also, what does it cost for that kind of work?
Ian,
It's a race engine...therefore it should have a shorter service life...also the valves should be checked every 2-3 race weekends
if it was a street engine....what is the shorter service life...10k....15k..????before the valves mushroom
another option is to get 1-2 mm bigger valves and have a valve job done
and check the valve clearance before you reassemble the engine just reassemble the head with cams
Maybe I'm confused, but since I am short of clearance, dont I actually want smaller valves rather than bigger ones? Or does bigger mean something different to longer? I just spent $200 on having the head reworked and two new exhaust valves installed so I'm kind of surprised at the current situation.
The valve situation arose because I took the bike to the track after buying it without checking the clearances myself. My mistake for trusting other people to do things right, should have checked them myself and then the current situation would have been caught earlier.
bigger valve will require the seats to be cut....wider...therefore the valve should be sticking out a bit further...therefore better clearance
check out kibblewhite...valves.... they make them in SS and could cut them 0.010 or what ever shorter so you have plenty of room for shims
they are pretty cheap...15-20 bucks each i've heard 12.....
They make a GS500 kit.
blackdiamondvalves.com
Cool.
Srinath.
I mentioned before that my old 97 GS had the original intake valve shims in it and adequate clearance at 80k miles. And yes sledge, considerable exhaust valve seat regression does occur on the GS's. At the same 80k miles, one exhaust valve had the min 215 shim and the other was close to it.
IL_Rider, since the intake valves are to spec now I'd leave them alone if they were mine and I would consider grinding the ends off of the exhaust valves. I really wouldn't expect any mushrooming or significant wear at the ends of the ground off exhaust valves, they seem to be as hard as rocks thru and thru. There seems to be a little over a millimeter sticking out of the valve keepers so I'd probably grind off a little more than half of that. Should increase required shim thickness from 1.65 to 2.15 or so. The bucket has a raised pad inside it that contacs the end of the valve.
(http://img.photobucket.com/albums/v443/jcp8832/valve2.jpg)
My 02 GS had a sticking exhaust valve bucket and with approx 21.5k miles on it, I cranked the engine one very cold morning and it stopped with a bang! That exhaust valve stuck open and it's head was broken off. Fortunately it crashed at cranking speed and only broke off the one valve head. That very hard exhaust valve nicked the edge of the intake valve and grooved the piston top a bit but the exhaust valve head itself was not marked, it just broke off like a full hardened thru valve stem would.
(http://img.photobucket.com/albums/v443/jcp8832/valve1.jpg)
I just replaced the broken valve and the tight bucket with parts davipu sent me and also lapped in both valves to make sure the intake valve wasn't bent a bit. Only had to buy the head and cyl base gaskets and she's been running like new for two more seasons with about 42k miles on it now and I expect it to go another 40k like the 97 did. :thumb:
If a reasonable fix couldn't be made, I think buying a used head assy would be less expensive around here than getting someone to replace valve seats.
I don't see why one side of the case hardened shims couldn't be ground off and placed down in the bucket recess with the remaining hard side up to take the cam wear. I was considering doing that on the 97 next time but it was totaled, retired, and replaced with the 02 before further valve adjustment was required.
All valid points Gents.............here is a good site all about valves. Lots of info, the failures section is very good.
http://www.gsvalves.co.uk/surface_treatments1.htm
So if I want to grind the tips on the valves, is this a job for a professional? I guess that surface has to be perfectly flat and perpendicular to the valve stem in order to minimize stresses in the valve stem? Looks like it would be very easy with the right tool, but not one that I have!
calculate your clearance
then calculate the amt to grind off to get you back into the middle of the valve shim range
then go to a machine shop and have the tip ground down
job done, clearance achieved - thanks for all the help! Just waiting on the new shims now. Just for future reference, I had 30 thousandths ground off the tips and that was as close as you would want to go. I think we calculated the original clearance gap at 65 thousandths (1.65mm) or so. I suppose this might help someone figure out how much to grind off their valve tips if they get into the same situation.
Nice, back on the road finally :thumb: ........almost
Good luck :cheers: