head gasket leak, 85 yamaha 90 2 stroke

[mcclaine]

i have a 85 yamaha 90hp 2 stroke rebuilt in 89. engine runs fine but was getting an overheat problem even after replaceing the water pump twice. i was told to remove the water jacket and exhaust cover from the left side of the engine and clean out the salt and corrosion. while i was doing this i also removed the head gasket and cleaned the water jackets around the head. i replaced all gaskets with yamaha oem gaskets and torqued bolts as directed. i used a dremel brush to clean mating surfaces. the mating surfaces were normal for an engine of this age, however in retrospect their were some areas with minimum pitting. when installing the gaskets i did not use any gasket sealant as yamaha did not reccomend it. when starting the engine i have a leak at the head gasket on left side. my question is 1) should i use a gasket sealant and try again. 2) can i use a dremel stone or flat file to lightly flatten the mating surfaces or do i need to have this professionally done. if so how do you machine the motor head surface which can not be removed from the engine without disassembly. thanks, mac

[99yam40]

I would use a piece of wet sand paper on a flat piece of glass or other real flat and smooth surface. Use a figure 8 rubbing motion with even pressure, keep water running on it to keep metal washed away,and rotate the piece from time to time to make sure you end up taking off metal evenly from all edges.
The only way to do the head surface is to remove it or try a flat file in place but you may not be able to get to all the surfaces evenly and cause even more problems.
I would not use a drimel or any rotating power tool on the machined surfaces because you remove metal from only a few places and not the whole surface.

[mcclaine]

thanks

thank you for the response. do you have an opinion on the use of a silicone sealant. also when i replaced the head gasket, it was with a new gasket that i had bought 10 years ago. it is cork and the gaskets that i replaced on the water jacket and exhaust were a synthetic neoprene of some sort. are the more recent head gaskets made of the neoprene or cork. should i invest in anew gasket? thanks, mac