Honda does not provide a gasket. I have always used, and highly recommend Loctite 574.
I used to be the service manager at a Porsche shop, and this also is what Porsche uses on their split crankcases.
Quote:The Loctite 574 sealant is an orange gooey sealant that cures in the absence of air. When you assemble your case and mate the case halves, you will have some squeeze-out that will collect at the case halves. If you leave this excess sealant exposed to the air, you will find that it will not harden. While this may cause you some head scratching, you shouldn’t be concerned, as the sealant is designed to seal within tight clearances, and between metal surfaces. Despite the fact that it appears that the Loctite 574 is not curing because the squeeze-out has not hardened, it has in fact properly sealed between your two case halves.
Because of these unique properties, Loctite 574 is perfect for motors -- there is no need to worry about the squeeze-out clogging your oil passageways, etc.
It is not cheap, and you will have to special order/mail order it. However, it is the correct sealant for the job. Best of luck assembling your motor!
Peace and grease,
-fang
