Head gasket question

[DougErickson]

My 73 HD Sprint 350 has no head gasket, the earlier 250s used a copper ring but the 350s have nothing. I have an official shop manual and it shows nothing, I have a scoured the internet and there is nothing.I have two unused gasket kits and there is nothing. so figuring the Italians know what they are doing that's how I put It together. I started it last night to test my ignition conversion and it ran great except I was hearing the dreaded pffft sound of leaking compression, slight but it was leaking at the cylinder/head joint. I checked the head bolts and they are torqued right. So any ideas? Is there an appropriate glue? Cut a ring of copper/brass/ lead? Look for an asbestos gasket I can cut down (maybe I could find an outboard with the same bore)? I don't want to give up a lot of compression to a thick gasket if I don't have to. I am open to ideas, Thanks Doug

[John H]

Hey Doug,
One of my Harley parts books shows a thin copper head gasket ring in there. If that doesn't stop the leak the head needs
to be lapped onto the cylinder. Ron's Goldstar had a similar issue. I refaced both the cylinder and head to correct the problem.
You are welcome to use my lathe and mill if that helps.

[DougErickson]

Thanks John, Does your book specifically show the ring for the late model 350 or just the earlier 250s? It sure seems like it should have some sort of gasket but my book shows nothing in the exploded diagrams and there is no mention in the text either. I like the lapping idea, Thanks, Doug

[John H]

Doug,
Looks like the thin copper head gasket is for the 125, 175 and 250. I would just do a lap job if the top of the cylinder is
in good condition.

[DougErickson]

I called the sprint people at Lancaster Sprint and it is true that the 350 does not use a head gasket so I pulled the head off and it was obvious it had been leaking near the pushrod tube area. I pulled the gasket for the pushrod tube off and reassembled things. Then I mic'd the gap for the gasket and got .032 but the gasket is .080 so it was keeping the head from seating fully onto the cylinder and thus the leak. I lapped the joint and put it all together and it started right up, though now it seems too rich, but that is a whole new problem! Compression tested at 190 psi- yippee!

[John H]

Glad you got it sorted out Doug.
So, you have to put the head on then measure the gap for the pushrod tube and find a gasket that will seal without distorting
the head? Kinda like the Goldstar head where you put the head on then measure the gap between the head and the cylinder muff. What ever that dimension is, the head gasket must be .003 thinner. This is to eliminate any distortion. Crazy.