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Old 12-31-2012, 05:54 PM   #1
RayAlazzurra OP
Stuck in the Eighties
Joined: Sep 2006
Location: St. Louis, Mo, USA
Oddometer: 241
2-stroke copper base gaskets--ke100?

A copper base gasket is probably a terrible idea for a 2 stroke. It would transfer more heat to the crankcase costing power, and it may not seal very well.

Even so I am considering having a custom copper base gasket made for my KE100. Base gaskets on this little bike only last a thousand miles or so before they are squished all to hell and fail to seal. The ring seal is still good at this point, so I am forced to renew the top end more often than otherwise due to gasket failure. My local Kawasaki shop mechanic is also a KE 100 rider, and he has replaced his base gasket about 5 times. The problem seems to be thermal cycles. Every time the little engine gets hot the cylinder expands and crushes the base gasket. The gasket deforms plastically, and the head nuts start to get loose. Re-torque the head, and the problem slowly gets worse with each thermal cycle.

We have tried making sure that the mating surfaces are perfectly flat. The shop guy has even removed the studs and lapped the cylinder to the case to assure a perfect fit. 1000 miles later the base gasket is starting to squish out from under the cylinder.

The KE100 uses an annealed copper head gasket and it seals pretty well. The head gasket also has a lot more surface to seal between the combustion pressure and the outside. The base gasket is only a few millimeters wide in places. The copper head gasket is used without any type of sealant. I wonder if pre-coating a copper base gasket might make it seal for a while? Btw. I checked with Cometic and they do not make an improved KE100 base gasket.

If anyone has any experience with this issue on any 2 stroke bike--not just the KE--please advise.

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