Shims

[bluevector1]

I picked up a 2005 kx250f that doesn't run. The first thing I did was check valve clearances. 3 of them are good and the right intake is tight couldn't get feeler gauge in. I can't read the shim so I will get micrometer tomorrow. What I'm wondering is what is the smallest shim you can use before you need new valves?

[joshgardener]

I didn't measure the shim size. I just made it so all the intake and exhaust clearances are running in at .17 which made my bike start better but also reduced the backfiring and gave it abit more response

[William1]

Shimming and valve replacement is not based on the smallest shim. It is based on how worn the valves are.

 

Say you have anew bike. You run it 100 hours, it needs a re-shimiming, just a single size. Fine to do. Reshim. Next time the valves are too tight, time to do a real valve job.

Or

If you need to go several sizes down in shim to get enough clearence, time for a valve job.

 

 

There is no such thing as a 'Stock Shim Size' .Shims are an adjusment based on manufacturing variations, a shim is selected, Future shim thickness is based off of that particular bikes requirments.

[bluevector1]

Thanks for the replys. I think the other owner didn't have another shim when he put it back together. He had the timing off too. I tore engine down to the piston and am measuring everything to spec as manual states.

[William1]

A nine year old bike, used from a questionable owner.

New valves, springs, retainers, cam chain, tensioner, piston, rings, other parts if needed/out of spec.

[250Kawi]

I agree with william1 your going to want to go through and replace anything that questionable.