Re: Re: Re: Re: Frozen valves


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Posted by Rick Denney on May 08, 2002 at 10:10:17:

In Reply to: Re: Re: Re: Frozen valves posted by Kenneth Sloan on May 08, 2002 at 00:19:45:

Assuming the valve is not bent or stuck because of some trauma, you might try the Lava soap lapping method that Joe has described. Lather up Lava soap in your hands, and coat the piston with the lather. Insert it into the casing, and move it back and forth for a while. Thoroughly rinse the horn, and see if you made progress. Repeat if necessary, but if twice through this process doesn't fix it, then take it to a technician. Anything stronger than Lava soap's fine pumice should also be left to a technician.

The warnings against spinning the valve in the case is based on putting horizontal scratches in the piston. These could indeed exacerbate a sticking problem, it seems to me, and the scratches probably ought to be buffed out (which is a high-risk operation). But turning while inserting would put a diagonal wear pattern, which should not be a problem. Car engines are honed at a 45-degree angle on purpose. This gives enough tooth to help seal the piston, but not so much that it promotes undue wear. And it does help the piston to establish its characteristic wear pattern most cleanly.

I would also remove the tacquet and piston spring before this exercise to avoid accidental damage and to ensure that the lapping extends to the bottom of the stroke.

Rick "who had to lap his Yamaha valves to get them to break in" Denney


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