One cylinder wont fire!

[Paulcet]

No "test shim" by name. It is just a shim that is known to be too small.

[junk301]

I could just buy one shim to test both right..replace, measure than replace the other exhaust valve the same way, measure, than buy the 2 new ones....Question. Does anyone know what shims come stock in the gs500 engine. I doubt a valve adjustment has ever been done on my bike before.

[adidasguy]

There is no stock shim size. There are ranges of sizes that are most common. I would guess that's 260 and 265 since I have so many of them. The slightest difference in machining will cause a different shim size.

[gsJack]

Close to what adidas said, my 02 came with two 265 and two 258 shims.  My 97 had a 265 and a 262 on the exhaust valves, never had the intake shims out to check them since they went 80k miles without a change.

http://www.gs500.net/gallery/data/500/GSvalvelogs.jpg

[junk301]

Update. Alright so its been a long time since my last update but here it is.  To remove the old shims i tried loosening the cam journals to a clearance of 0.03. I could get the shims to rotate but not the buckets...I can only think that something is wrong with the buckets. Whats my next move.  Taking off the cam shaft??

[patchesroy]

My bike had issues where only one cylinder was firing, then i found that one of the magnets on the signal generator was complete abliterated. so i replaced it and it worked

[Destiny2191]

My 94 engine that I've just replaced was firing on one cylinder for a day, whole bottom end then blew shortly afterwards!

People above seem to have suggested good things to check for, so for now I'll leave my oar inside the boat!

[junk301]

thanks for the responses..But does anyone know if i need to take off the camshaft? I cant find any info on this. helps appreciated

[gsJack]

Update. Alright so its been a long time since my last update but here it is.  To remove the old shims i tried loosening the cam journals to a clearance of 0.03. I could get the shims to rotate but not the buckets...I can only think that something is wrong with the buckets. Whats my next move.  Taking off the cam shaft??

Next move depends on what you want to do.  Tight buckets are not good, very tight ones are even worse.  I had a very tight one on my 02 GS, so tight it held an exhaust valve open when cold and there was no compression pop checking it with the thumb over the hole and cranking.  I put a screwdriver in the bucket notch and hit it with a hammer trying to turn it and it wouldn't budge.  Aluminum expands more and faster than steel when heated.  Starting the bike it would run a bit rough at first but then smooth out in less than a minute and run like new the rest of the day.  I decided to let it go until next check to see if it would wear in and loosen up but about 10k miles later I cranked it one freezing cold morning and bang.  Valve stuck wide open and was broken off while cranking.  I pulled the head to repair it with new valve and bucket and it's gone another 75k trouble free miles since.

That bucket was so tight I had to drive it out from inside with a long punch and heavy hammer.  Your buckets must not be that tight since they don't stick open but are closed down to little or no clearance when cold.  At this point I think I'd go ahead and change shims to get proper clearance first to see how it is, if you have a burnt valve it will be necessary to pull the head to replace it anyway.  If compression is restored you might be OK as is.  Your bike, your choice.  Getting those tight buckets out to change them can be very difficult.  You should be able to get the shims out by compressing the bucket with your tool.  I just pick them out with tweezers at the notch but some here lift them out with a magnet, they are not tight.

[gsJack]

junk301, your first consideration in your first post above might turn out being the best approach.  Tight buckets are a pain in the butt!  But if you have the test shim suggested in the following posts it might be worthwhile putting it in the right exhaust valve  to recheck compression to see if valve is burnt before going ahead.

Bike has very little power (120km/h high speed on highway).I compression tested both cylinders.  The left reaches 150 while the right stops at a measly 35ppi.  I have never had a valve adjustment.  Is a valve adjustment my first step or is there a quicker way to figure out the root of the problem? I'm considering simply replacing the top end(I have no garage and tinkering with the bike on the sidewalk may prove to be messy and bothersome).

Any input is appreciated.

P.S. plugs are fine, and both sides generate a spark..so I'm assuming the coils and electrical's are all fine.

Cheers!

[junk301]

junk301, your first consideration in your first post above might turn out being the best approach.  Tight buckets are a pain in the butt!  But if you have the test shim suggested in the following posts it might be worthwhile putting it in the right exhaust valve  to recheck compression to see if valve is burnt before going ahead.

Bike has very little power (120km/h high speed on highway).I compression tested both cylinders.  The left reaches 150 while the right stops at a measly 35ppi.  I have never had a valve adjustment.  Is a valve adjustment my first step or is there a quicker way to figure out the root of the problem? I'm considering simply replacing the top end(I have no garage and tinkering with the bike on the sidewalk may prove to be messy and bothersome).

Any input is appreciated.

P.S. plugs are fine, and both sides generate a spark..so I'm assuming the coils and electrical's are all fine.

Cheers!

Thank you so much for your post and very sorry for the late reply.  Here is my question. Since I am working on the engine inside the frame I cannot get to the shim notch with a screwdriver.  To take out the shim, would removing the camshaft be necessary? I dont mind doing this if it does not prove to be very time consuming.  Like I mentioned earlier both exhaust buckets are tight in this way. For your info, I have garage space for the next month so I don't mind tinkering with the top end myself.

[gsJack]

Mentioned above somewhere that I picked shims out with a tweezers at the notch but others just lift them out with a magnet in which case it wouldn't be necessary to turn the bucket to get at the notch.  Need to compress the bucket enough to get the shim out with the valve tool or with a couple of screwdrivers.

I'd snug the cam caps back down and put in the smaller test shim and then if you have clearance recheck the compression before deciding whether or not to pull head.  Make sure you stuff a rag in the cam chain slot in the center of the head so the shim doesn't end up in the sump when you pop it out.