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General Category => Maintenance => Topic started by: grannyknot on July 15, 2011, 06:02:01 PM

Title: Valve clearance confusion
Post by: grannyknot on July 15, 2011, 06:02:01 PM
1984 FJ1100
Yamaha service manual says to find top dead centre to measure valve clearance but how is that possible when at TDC both the exhaust and intake cam lobes are pointing at 90 degrees from the shim and are in contact with it?
I have always measured valve clearance with the lobes pointing straight up,180 degrees away from the shim
and have never had a problem, I just measured the fj this way and found 4 shims need to be traded for one size thicker. What am I missing here?
Thanks,
Chris
Title: Re: Valve clearance confusion
Post by: SlowOldGuy on July 15, 2011, 08:01:36 PM
Cam lobe should be 180 degrees pointing away from the shim.  BTW, that is NOT straight up since the valves are not vertical.

DavidR.
Title: Re: Valve clearance confusion
Post by: movenon on July 15, 2011, 10:10:05 PM
Maybe I am confused but "one size thicker" ? Generally the valve sucks in and you have to go thinner ? I can get confused so forgive me if I am off. :)
Title: Re: Valve clearance confusion
Post by: FJ111200 on July 16, 2011, 03:26:45 AM
As long as the base circle area of the cam is somewhere off the face of the shim, and not the flat side and/or the lobe end of the cam about to come into contact with the shim, then you will get a reading or measurement.
Title: Re: Valve clearance confusion
Post by: grannyknot on July 16, 2011, 05:39:42 AM
Thanks for the confirmation.
Title: Re: Valve clearance confusion
Post by: grannyknot on July 16, 2011, 12:50:53 PM
Quote from: movenon on July 15, 2011, 10:10:05 PM
Maybe I am confused but "one size thicker" ? Generally the valve sucks in and you have to go thinner ? I can get confused so forgive me if I am off. :)
thinner was what I meant, somewhere between the garage and the keyboard...  breathing in too much carb cleaner I think.