I checked my valve clearances and my exhaust valves (both) won't allow a .03mm feeler gauge to slip in. So I take out the shims and both shims are labeled 2.78 (also measures this exactly with my digital caliper). This is my first time doing a valve adjustment. From everything that I've read, I was expecting a number divisible by 5; i.e 2.80 or 2.75. Additionally by everything else that I've read, I need to go with a shim thinner by .05mm, which means a shim that measures 2.73. I've read they only come in numbers divisible by 5, so I'm confused and not sure what to do.

What size shim do I purchase for this bike? Do I need to do additional work to determine the required shim thickness or do I have enough information to make this decision? I really do appreciate any help you guys can give me.


My bike is a 2001 with 25k miles on it. The valves have never been adjusted. The intake valves measure within spec but the exhaust valves can't get a .03mm gauge in. The bike is extremely hard to start. I have to turn the engine over for several minutes, almost to the point that the battery is dead before it will start. Then it's hard to keep the bike idling. It wants to die. I keep the choke on until the engine warms up. When fully warm, the bike will die at idle. I've adjusted the idle screw but that will only make it idle at higher RPM's. To keep an idle around 1200, the bike will always just die. But I can play with the throttle to keep the engine running and can ride the bike with no other issues except when I came to a stop, I have to give it a little gas to keep it running. Other than this, the bike runs strong. I've taken the carbs off and checked them but they're clean. I had a shop clean them a few thousand miles ago.

I'm really hoping the exhaust valves being too tight are causing this issue. Can I please ask for opinions on this? Do my symptoms match the valve clearance being out of spec?

Yes, those symptoms sound exactly like valves that are too tight. At 25k without a valve check you are lucky the bike still runs at all.

The bikes come from the factory with custom shims. Its actually nice to find some in those odd sizes because they can help with getting the correct clearance. When you buy them new they come in .05mm differences.

Assuming your buckets still turn, lets assume you have .01mm of clearance. Going to a 2.75 will only get you to .03mm, which is too little.
Going to a 2.70 will get you .08mm of clearance (perfect by Suzuki standards). You could also get a 2.65 for .13mm of clearance which is on the wide side of things.

Some people around here like to run their valves with wider than stock clearance with the idea that cooler valves will not wear as fast. Considering that we do not know your exact clearance at the moment, I would be hesitant to put a 2.65 in the bike.

So, to answer your question, you want 2.70 or 2.65mm shims depending on your preference for Suzuki or GStwin specs.

Well Bluesmudge pretty much explained it all...

Just a couple of hints....what size are your intake shims?  It is possible to maybe swap them to the exhausts just to get an accurate measurement, so you know what to order...

Also...I when I first ordered shims, I got a few sizes, anticipating the future...and saving shipping costs.  Plus I didn't want to get "stuck" in case the size I ordered was not correct...then you have to re order and pay shipping again, and wait a few days...

Now the bad news, (possibly)....running 25K without a valve clearance check is a very, very bad thing!  If the bike has been run for a while with the exhaust valves not closing fully, there is a good chance of burnt valves!

I'd first get the shims correct, then do a compression test...to see if the valves are OK...

Hope for the best!

Cookie

Thank you both for your answers. I had a heck of a time finding shims. Both Suzuki shops in my area (Sacramento) did not carry 29.5mm shims. And a call to other non-Suzuki shops provided no relief either.

Long story short, I have installed new 2.70 mm shims. Right exhaust valve now has .09mm clearance, but left exhaust valve does not let a .02mm feeler gauge in.

So I've ordered 3 more shims: 2.65mm, 2.60mm, and 2.55mm. It's frustrating buying a part that doesn't give you what you need, so I figure buying the next 2 sizes of smaller shims will avoid me buying more if the 2.65 is still too tight.

Once I can get the shims to the correct clearance, I'll check engine compression.

Thanks again for your advice.

SUCCESS!!!

I received the new shims and installed them. Funny that the left exhaust valve required so much more adjustment than the right. Both initially had 2.78mm shims. The right took a 2.70mm shim and now has .09mm of clearance, but the left shim, I had to keep going down to a 2.55mm shim and this only provided .04mm of clearance. I really should be purchasing a 2.50mm shim, but I'll wait until the end of the summer to change it.

So after getting proper adjustments out of my exhaust valves, I put the bike back together (with some minor fuel line issues) and attempted to start it up. As soon as the carbs began to receive fuel, the bike started up IMMEDIATELY. It has not done that in a long time (i used to have to crank it for several minutes). I didn't let it warm up. I stopped the bike and attempted to cold start it again, and it again started up immediately. Oh this is such a good feeling to fix my own bike rather than take it to a shop! I won't be able to test ride it until I get new fuel hoses because I had some issues, but I have a positive outlook that it'll ride great.

Should I still check engine compression even if the bike rides great?

Thanks to everyone on this board for being so knowledgeable.

If the bike rides great, I see no reason to check the compression. Although it will tell you if you are within spec. That one exhaust valve must have had ~0 clearance. I'm surprised your didn't mess up your valves.

Glad to hear everything is working out. Congrats on sticking with it and learning along the way. A GS with correct valve clearances always seems much happier.
Don't wait too long to throw the 2.50 shim in there. The exhaust valves will go much longer between shim changes at .09 clearance.