valve clearance increased during break-in?
Posted March 19, 2008 - 04:03 PM
rebuilt my top end last summer, had to take it apart this spring to repair what looks like a bad seal on the coolant race. Anyway, when taking it apart after having broken in the top end rebuild (brand new head, valves, cylinder and piston), i took the cam lobe-valve lifter bucket clearance measurements.
I was surprised to find that they appeared to be WAY out of tolerance, with too much space between cam lobe and bucket. I know i sized the shims correctly when assembling it the first time, and i know over a long time the valves should actually STRETCH, not compress, so if anything, running the engine should make the tolerances smaller, not larger. Even with that, i would not have expected any change at all, much less this large. I've certainly double- and triple- checked that i am using the correct units on the feelers and in the manual. only difference might be that there was a lot more oil on the feelers and in the cam lobe area than when assembling it for the first time, so maybe this made one or the other of the readings less accurate? easier to slide the gauges in with a little oil?
anyway, any thought would be appreciated. i'm going to put her back together and give her a shot this weekend, either way.
Posted March 19, 2008 - 06:38 PM
PS- My shims were from a Hotcams kit, not oem replacements.
Posted March 19, 2008 - 09:23 PM
I had the exact same problem after my last adjustment with the valves being 0.1-0.20mm out of spec.
I too was worried about it and posted a thread on this forum, see this link
http://www.thumperta...=BIG valve gaps
My mechanic (ex Honda Japan) assured me the while valve stretch is the norm it is not uncommon to have to shim for bigger gaps and not to worry about it, just rebuild it and ride.
So thats what I did and after putting it back together glad to report I've had about 700 trouble free km's.
Next valve check coming up soon.
Hope this helps.
Posted March 20, 2008 - 09:00 AM