how much valve lapping is enough?

[p_s]

I get a smooth even matte surface on the valve and seat. I clean it up, put it together, pour acetone down the port, and it leaks very very very very slowly. It takes at least a minute for a drop to drip from the head to my worktable. Is it good enough? It doesn't take much lapping to get it to this point, but it seems like more lapping doesn't help at all.

I'm using Permatex grinding paste, which only comes in one granularity. Good enough?

[Suzuki mad]

You should have a nice even circle around the valve and valve seat of about 1.1 to 1.3mm (0.04 - 0.05in) in size with no pit marks what so ever and have a velvety finish. If its larger than 1.3mm then its over the service limit.

The valve seat can be recut but I've never done.

As for leaking, I've never tried that either.

Suzuki mad

[rapidray]

You are good to go! Stop lapping & start cleaning & assembling! Ray.

[p_s]

Thanks, y'all. I measured the circle at 1-1.1 mm--that's the spec for the tiny GS550ES valves. I still have 9 or 10 valves to go--although the intake valves look just about perfect already.

(The big 8 valve heads must be a breeze to rebuild.)

[Old Colt]

It is tough to use acetone as a leak check since it is a very strong penetrant.
If your valves are even slowing down acetone you got them right.
Mineral spirits and Stoddard solvents are used more often and being a heavier body they are held back easier.
So if yours are holding acetone, you have a very good finish on them.
Make sure you get oil soaked back into the guides since the acetone will dry them severely.