Thread: Reshaping/Fitting Gas valves
09-03-2007, 10:36 AM #1
Reshaping/Fitting Gas valves
Guys - How do you reshape the metal for a gas valve ? I bought some that I thought were for a 12r and as it turns out they were cut for non standard pistons. It seems ilogical that if they have been cut they can be reshaped to the correct diamiter.
09-03-2007, 11:45 AM #2
If they were cut for a larger piston then they should be fine for your OEM bore 1200. The reason they cut them is to clear the larger ring diameter. Pull the head while installing them and check the valve to piston ring clearence with the valve all the way down against the seat.
09-03-2007, 12:13 PM #3
The person I bought them from said a smaller piston ? . I can see reshaping it to match the existing valve but I would be missing material and not sealing.
Use a file to reshape it ?
09-03-2007, 01:23 PM #4
To properly shape a valve to a piston, put the valve completely down without having it hooked up to anything. Take a ring and push it down (using a piston so it is straight) to the place where the clearance is the smallest between the ring and the powervalve. Measure with a wire feeler guage. Clearance should be .020" to .030" per Lowell. I use a belt sander to shape the valve. The end where the belt goes around is almost perfect to the bore of the engine.
you can do this on the ski by rotating the crank so the piston is below the exhaust port. Be carefull not to drop anything into the engine. I use wadded up paper towells to cover any openings.
09-03-2007, 05:37 PM #5
if I reshape my valve will be a touch shorter - is that ok ? I will keep in mind the clearence to the rings but the overall length will be shorter since the valve has been shaped already.
09-03-2007, 06:43 PM #6
Maybe just a smidge shorter but better than hitting the piston
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