Posted by Chuck(G) on April 07, 2002 at 11:22:55:
In Reply to: Lapping Pistons with Lava Soap posted by Ian Easton on April 07, 2002 at 08:19:09:
Lava soap's active abrasive is pumice, so the local product sounds similar. But the trick is to whip up a froth with it and use the froth, not the soap itself, which contains larger particles and could cause your valve to jam.
If your valve requires only a light lapping, you may want to consider two things that I've tried: toothpaste (really!) or an abrasive metal polish such as Brasso. Both have done the trick for me, with toothpaste removing the least metal (i.e. slowest working).
I think someone else may have suggested Bon Ami powder (feldspar being the abrasive).
Regardless, after you're done, rinse out the horn really, really well!