So I Checked My Valves Today...

Intake: All are at .008 or so

Exhaust : Range from .016 to .018

All have 186 shims in them, one has a 189 (an intake I think). Im away from home and dont have my manual with me, so I dont know anything about these shims.

Would I be able to shim these again, or has the tough exterior coating of Ti been worn off my valves? How much does a head rebuild typically cost?

I probably shouldnt ride it like this, should I?

Thanks guys.

You have given your readings formatted as if they were in inches, and if that is true, you need to double check them because they are all exceptionally loose.

If you meant .08 and .16, .18, that's different. In that case, you need to reshim them to the right range and then recheck them in after each of the next 3 rides to see if they are holding at the new settings. If the hard coat on the valves is gone, they will quickly tighten up more. If it was just the seats wearing a bit, they'll stay stable.

Sorry your right, .08, .16, etc.

So, if Im doing this right, if my intake is at .08, and it has a 186 shim, I will need a 182, to make it .12, right?

Sorry your right, .08, .16, etc.

So, if Im doing this right, if my intake is at .08, and it has a 186 shim, I will need a 182, to make it .12, right?

That's correct, but unless you have a collection of factory installed shims, or use one from a Honda , or find a 182 in another part of your engine, you won't be able to get a 182. (Yamaha uses shims in .01 increments at the factory, but sells service shim only in increments of .05. Honda sells them in .025mm slices)

Your choice is between a 180 and a 185. The clearance is too small, so the shim must be thinner to get the right clearance. Your clearance is -.02 of spec. Your current 186 minus 185 creates only .01 more clearance; not enough. 186 minus 180 yields .06 more. .08 + .06 = .14, which is in the specified range, and therefore good.

You can, if you find them in your engine, use shims ranging from 179 ~ 184 to get the clearance between .10~.15mm.

Awesome, thanks alot Gray.

I have just 2 remaining questions:

1) If Yamaha only sells them in .05 increments, and I have assorted sizes like 186, and 189, than these are the original shims that came from the factory, which means that the guy before me never adjusted the valves. He said he never opened up the engine- but I would have thought that he would have checked valves. So its due for that valve adjustment after you ride it a few times when new, right?

2) How do you find time to sit here and post all this stuff? :p

Awesome, thanks alot Gray.

I have just 2 remaining questions:

1) If Yamaha only sells them in .05 increments, and I have assorted sizes like 186, and 189, than these are the original shims that came from the factory, which means that the guy before me never adjusted the valves. He said he never opened up the engine- but I would have thought that he would have checked valves. So its due for that valve adjustment after you ride it a few times when new, right?

2) How do you find time to sit here and post all this stuff? :p

1) It doesn't mean he never adjusted them, but the odds of that are good. I owned an '03 that never had a valve adjustment up to at least January '08, and it had hundreds of hours on it. He could have just shuffled the shims around a little, and/or used some used ones from a tech's collection, too. The fact is that an awful lot of the Gen1 YZ450's just never needed an adjustment until now. Ever.

2) I'm actually a team of 5 people.

Haha, thanks alot Gray. Your knowledge of these bikes is just incredible.

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