Modern Vespa

I checked squish on my Malossi 166 and it's over 2mm, so I need to lap/plane it down almost a mm or so, but am concerned that if I do so, it will not leave a deep enough groove for the head gasket.

Anyone know the limit to how much you can lap down a gasketed head?

you're talking about the groove for the o-ring?

edit: did you do a 4 corners test w/ solder when measuring the squish?

Yes, that's what I meant.

I'm used to my crappy non-o-ring'ed DR's and don't know all the correct terms for my fancy Malossi.

I was just making sure we were talking about the same thing.. my terminology may not be correct either.


IIWY, I'd either send the head to Al, have hi take off .5-1mm off the head, put a new groove in.

OR.. you could lap the head .5mm or so... use some Permatex Ultracopper and go w/ that. Fill what's left of the groove w/ the Copper, omit the o-ring, then do a light smear aroud the head and go from there.

OR.. OR.. you could send the barrel to Al and have him take it off the top of the barrel..

I considered sending it to Al. I'd have to throw a different top end on there to do that, though, since it's currently my daily rider until I get around to finishing up replacing the bent fork on my VBB. If I did that, I'd probably spring for the BGM 177 and be done with it.

My LML cases are a tiny bit too long, I think, because I've had to lap down every kit I've ever had on them to get proper squish. I've considered going to a 60mm crank to help fix that gap, too.

If you take 1mm off, I wonder if the compression may be too high?
If it was me, I'd do what V says and ditch the o-ring and use the copper stuff instead.

Squish is 2.6mm right now, so I'm not too worried about compression. I used the copper stuff on my DR's for years and while it wasn't perfect, it was good enough.

This head is hosed anyway--I cross-threaded a spark plug and had to put a helicoil in it, so a little experimentation on it can't hurt too much. And if I decide I like the results, I'll get a new head and send that one off to HRA to be done correctly.