Valve Clearance question?

[desmodoktor]

i was going over the Haynes book and i dont understand something abt the valve clearance.
whats different btw Checking Clearances and Assembly Clearances ?
is it when the clip of the rocker arm is on and off? im guessing since the measurements are different when the clip is on and when its off. please let me know thank you!

[Speeddog]

My understanding:

Assembly clearances are what you go for when you're building the motor.
Checking clearances are what is acceptable when doing the valve clearance check.
If they're found to be outside of those checking clearance ranges, then they should be re-set to the assembly clearances.

FWIW....
I don't agree that those checking clearances are reasonable.
2-valve bikes that come in with closer clearances ~0.20mm generally run crappy.

I check and set the clearances with the clips out.

[desmodoktor]

My understanding:

Assembly clearances are what you go for when you're building the motor.
Checking clearances are what is acceptable when doing the valve clearance check.
If they're found to be outside of those checking clearance ranges, then they should be re-set to the assembly clearances.

FWIW....
I don't agree that those checking clearances are reasonable.
2-valve bikes that come in with closer clearances ~0.20mm generally run crappy.

I check and set the clearances with the clips out.

sounds good. i ll do that!  thank you !

[Lieutenant Dan]

FWIW....
I don't agree that those checking clearances are reasonable.
2-valve bikes that come in with closer clearances ~0.20mm generally run crappy.

Are you saying the clearances should be looser than what is listed? If so, why would tight clearances make a bike run crappy?

Thanks,
Dan

[Raux]

correct me if I'm wrong

but IIRC

openers should be towards the upper end of their range.
closers should be closer to the low end of their range.

[Dirty Duc]

Are you saying the clearances should be looser than what is listed? If so, why would tight clearances make a bike run crappy?

Thanks,
Dan

Nope, Speeddog is saying that closers should be on the tight end of the allowable spectrum.  Once they get out somewhere in the vicinity of the loosest spec they don't hold the valves quite as closed as makes the engine happy.

correct me if I'm wrong

but IIRC

openers should be towards the upper end of their range.
closers should be closer to the low end of their range.

That's how I do mine.  Openers tighten over time, closers loosen over time.  I think.  My brain could be addled by too much work.

[Speeddog]

Nope, Speeddog is saying that closers should be on the tight end of the allowable spectrum.  Once they get out somewhere in the vicinity of the loosest spec they don't hold the valves quite as closed as makes the engine happy.

Yes, that's what I was meaning.

That's how I do mine.  Openers tighten over time, closers loosen over time.  I think.  My brain could be addled by too much work.

Yes, that's the case.

A customer recently had a an '05 M620 with ~21k miles on it, trucked in because it wouldn't run.

Exhaust closers were at .009" and .013", and exhaust openers were zero, actually they were holding the exhaust valves open...
It wouldn't start because it didn't have enough compression.