half moons

[DeanR]

Trying to seal up a leaky half moon plug. I have a new one to put in and I have black RTV and Yamalube 4. Is one any better than the other and any tips on getting this sealed up right the first time? I've had good luck putting no sealer at all on the valve cover gasket. The only problem has been at that darn half moon. Thanks.

[John]

YamaLube or YamaBond? There is a big difference. YamaBond 4 will work good, probably better than 'Sillycone'. It works great sealing up the crankcase joints..

[DeanR]

sorry, mispoke, I did mean Yamabond.

[pathfinder]

Yamabond # 4 works the best. IMHO

[Winterhawk]

According to Bob Jones He says that the half moons should be installed on a clean dry surface with absolutely no sealer of any kind. I've done it this way and it works great.

[prometheus578]

Maybe with new ones. But with old, brittle ones, I'd clean the surfaces with Brakleen and then use your sealant of choice.

[DeanR]

Haven't yet closed it up. I did notice that the new half moon when inserted sits very slightly higher than the rim. Has anyone noticed this? Maybe as you tighten down the valve cover, it depresses the half moon enough for it to fit flush?

[prometheus578]

Yes, it will then fit flush, and "pressure seal" the lower area. My concern with old ones is that they might have hardened and will not "pressure conform" to the half-moon shape of the head.

[DeanR]

No sealant at all with the new one?

[prometheus578]

I seal everything!

That way, if it leaks, I can't yell at myself... "You idiot... why didn't you use sealant?"
(Of course, if something leaks with sealant, then I just yell, "You idiot!)

[Winterhawk]

You just have to trust me. No sealer on the new ones.