Valve clearance slightly out of spec - Safe to continue riding ? | GTAMotorcycle.com

Valve clearance slightly out of spec - Safe to continue riding ?

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il3dsm

Well-known member
I checked valve clearances today and they are as follows:

Intake - .13mm for both
Exhaust - .18mm one side, .20mm the other
Now the clearances should be .10-.20 for intake and .20-.30mm for exhaust.
This puts me right out of spec for one of the valves.
I've ordered a shim kit,but it will take over a week to get here.
Is it safe to keep riding the bike while I wait for the kit to come in? Or will I somehow cause some irreparable damage if I ride it for one more week slightly out of spec?
 
Yes, it's safe.
 
So you're tight .02mm on one valve. If I'm operating the inch converter properly that comes out to .000787 inches or 79% of a thou give or take. I'd run with it as well.
 
Yup, should be fine.
Valves tighten up, and gotta beware tight ones (not so much loose ones)...
Tight exhaust valves if ignored are trouble!
In theory, if that one valve was tighter - plus it was 40 degrees out, in July - and you went out and ran her real hard, that could be bad.
But this nice, cool spring weather should last us at least another week or so.
Actually if you're going to go in there, you should probably loosen up BOTH those exhaust valves and future-proof yourself somewhat...
 
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Personally, I'd open them all back up closer to the loose end. They will all need adjustment soon anyway, why not do it all at once while the cams/ buckets are out.
 
Anybody know why valves tighten up? Shouldn't they loosen up?
 
RockerGuy said:
Anybody know why valves tighten up? Shouldn't they loosen up?
Click to expand...

The valve clearances tighten as the valve seats "bed in" to the head. The further into the head it recedes, the more the clearances "tighten up".
This occurs faster than any wear on the cam lobe, bucket, shim or valve stem, which could allow the clearance to loosen (theoretically).
 
RockerGuy said:
Anybody know why valves tighten up? Shouldn't they loosen up?
Click to expand...

It's the valves hammering into the valve face. The clearance on the ends of the valves, where they are actuated, might increase a tiny bit as they wear, but much less than it decreases on the other side.
 
There go my brownie points
 
Yeah, from what I've read they can go back and fourth, but more common is tightening.

I've got my shim kit, going to work on it today.
 
Thanks for the response, I think I might need a diagram to see that. Gonna do some googling
 
Iceman said:
The valve clearances tighten as the valve seats "bed in" to the head. The further into the head it recedes, the more the clearances "tighten up".
This occurs faster than any wear on the cam lobe, bucket, shim or valve stem, which could allow the clearance to loosen (theoretically).
Click to expand...
Ok so this makes alot of sense now. I wonder if manufacturers ever thought about forging the seat, so there is minimal movement
 
RockerGuy said:
Ok so this makes alot of sense now. I wonder if manufacturers ever thought about forging the seat, so there is minimal movement
Click to expand...

The valve face kinda has to wear the way it does though, to keep a good seal between it and the valve. I think the only way to go from there are all the super experimental valve replacements (e.g. rotary valves) but none of them seem to gain any traction. It's fairly reliable, at least - since pretty much all cars have hydraulic lifters/other-things-that-aren't-lifters (having a mental brownout) that adjust valve clearance automatically it's more or less a solved problem. A few bikes have them but not many.
 
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