Well I took the beast on it's first small test ride today, bloody aftermarket gaskets, blew the left head gasket within 1k, so made my own this time, will test that tomorrow.
Hi again Chris- On my '66 G12CSR, I blew out two composition head gaskets, one in the first 1K, the second (same side) at about 2K. This was despite careful re-torquing and repeated warm up/cool down cycles on the new engine. Evidently, aftermarket composition gaskets often have this problem. AMC used a composition gasket with embedded wire mesh, but no one makes these any longer.
So I made my own solid copper head gaskets, about 0.040" thick, I think. LOTS of work! Made four of them. Have since found a local source for them (in Arizona, USA- Copper Gaskets Unlimited, available online). I annealed my handmade ones properly, and they haven't given me compression blowout problems since, with another 800 miles on the bike. Solid copper head gaskets for twins are now also available from the AJSMOC Jampot Spares scheme in the UK, and can be ordered online by members or non-members.
I did recently develop another head gasket problem with my solid copper gaskets- an oil leak between head and barrel on one cylinder. Reading over the years in the Jampot newsletters, this is evidently the shortcoming of solid copper gaskets. I pulled that one head off, and drilled out the oil feed hole in the copper gasket at the top end oil gallery on that side, to accept a viton "o" ring that was about 0.010" thicker in chord than the head gasket. There isn't much meat left in the copper gasket at tight spots, but if carefully located, it can be done.
I re-annealed that modified but original gasket, and re-installed it. So far, so good. I won't do the same fix on the other cylinder until/if a leak develops there. It's possible that the Jampot Spares copper gaskets can be ordered with "o" rings already installed.
Oh, another note- I sprayed the solid copper gasket with a high-temp copper silicone sealer this last time- that might also help well with possible oil leaks.
Thanks for the info on attaching photos. I will try that soon, but this posting has gone on too long again. Regards- Paul
Yes we did the same O-ring method too, so far so good, I'll take the bike for a decent run in the near future to really test it. Will also do a small video and upload it here.
Thanks for the lead on the copper gaskets, they have a ebay store too which makes for easy purchase.
