Does valve clearance get tighter or looser?

Just checked break-in valve clearance after ~12 hours.

Clearances look tight. Exhaust .007 guage fits easy. .008 guage a tight fit (should be .0079 to .0098). Intake can't get .005 to fit, don't have .004 (should be .0039 to .0058).

Do valve clearances usually get tighter or looser after break-in?

It usually gets tighter from the valves beating into the seats more and more. I have almost 500 hours w/o needing a valve adjustment and that includes one trip to sandmountain and one long trip to pismo. She still fires quickly too.

It usually gets tighter from the valves beating into the seats more and more. I have almost 500 hours w/o needing a valve adjustment and that includes one trip to sandmountain and one long trip to pismo. She still fires quickly too.

What were your clearances after break-in and how much have they changed in 500 hours?

Valves almost always get tighter. :crazy:

Is it unusual for the valves to start out tight?

Do the shims come from the factory all the same thickness or does it vary from bike to bike (and valve to valve on the same bike)?

Is it unusual for the valves to start out tight?

Do the shims come from the factory all the same thickness or does it vary from bike to bike (and valve to valve on the same bike)?

The valves are shimmed at the factory, and usually on the loose side. It would be rare to see a tight valve from the factory. The size of the shim depends on each valve for each bike.

The valves are shimmed at the factory, and usually on the loose side. It would be rare to see a tight valve from the factory. The size of the shim depends on each valve for each bike.

Sucks to be me... Wonder why mine are tight? I will buy a better feeler guage set and check again. Tool suggestions? :crazy:

Hi,

Just a normal feeler gauge which are used in cars. Should be found from a local automotive shop. When they assemble engine at the factory they use shims with different thikness. Mine has atleast 3 different thikness. My engine has 150 hours on it now and still no change on valve clearance.

Timo Mc

Sucks to be me... Wonder why mine are tight? I will buy a better feeler guage set and check again. Tool suggestions? :ride:

Dont worry about it, I checked mine after breakin ( after a couple of hours) and they were on the tighter side of the middle of the range {similar readings to yours] - I felt the manufacturers would have set them up with a bit more space as well :ride: , but its a production line remember!

So, if they are in the range then OK. The important thing is to see how they change...I will probably check mine again after another 1500km just for mental insurance. If little or no change then OK (which I suspect will be the case!)

:crazy:

on the plus side, your motor makes more power the tighter the clearances get.

on the plus side, your motor makes more power the tighter the clearances get.

Thanks for that Matty, you learn something every day! More valve lift I guess?

:crazy:

yeah, mee too, i'ts totally oposite compared to car engines who''s valve tolerances wear looser and have to be tightened up over time.

Hi,

Just a normal feeler gauge which are used in cars. Should be found from a local automotive shop.

Timo Mc

That's what I have now - with blades about 10 mm wide. I cut them length-wise to 5 mm wide and deburred the edges. .005 inch is my thinnest, so I may take the cut-off piece and try to grind it to .004. I think I saw some Pro Motion tappet feelers on the TT store that were thinner.

Just fishing for what tools others like...

That's what I have now - with blades about 10 mm wide. I cut them length-wise to 5 mm wide and deburred the edges. .005 inch is my thinnest, so I may take the cut-off piece and try to grind it to .004. I think I saw some Pro Motion tappet feelers on the TT store that were thinner.

Just fishing for what tools others like...

Just go buy a cheap set down at car quest or napa... :crazy:

Ground the leftover .005 piece to .004 (love that dremmel tool!) and will recheck the intakes. I hope it fits, don't want to reshim already...

does anyone have a pic of what the shims look like? these thumper bikes are all new to me, I was a 2stroke guy all my life.

Ground the leftover .005 piece to .004 (love that dremmel tool!) and will recheck the intakes. I hope it fits, don't want to reshim already...

I custom trimmed my feeler guages to fit between the cam caps. Keep us updated.

Bummer - I had to grind closer to .003 to get it to fit under 2 of the intake valves.

Correct me if I am wrong, but tighter means that the valve edge has just seated a little more deeply into the head, so there is no actual risk of engine damage by a valve hitting a piston since the cam is pushing the valve the same inward distance it did when it left the factory?

Thanks for that Matty, you learn something every day! More valve lift I guess?

:crazy:

Exactly! :ride:

Bummer - I had to grind closer to .003 to get it to fit under 2 of the intake valves.

Correct me if I am wrong, but tighter means that the valve edge has just seated a little more deeply into the head, so there is no actual risk of engine damage by a valve hitting a piston since the cam is pushing the valve the same inward distance it did when it left the factory?

Some relevant discussion on valve clearance:

http://www.thumpertalk.com/forum/showthread.php?p=3328332&posted=1#post3328332

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