RichG wrote:Skunkbait,
You need to consider the outer crank seals as well as the centre, namely the flywheel side. My bike's symptoms (starting, getting it off the line) sound very much like yours. Have a read of my experience, hope it is of help.
http://www.nsr250.net/forums/viewtopic.php?t=7023&postdays=0&postorder=asc&start=0

Maybe worth looking for a leak-down test kit, they are useful in diagnosing such problems......http://www.accu-products.com/accu-products/leakdown-test-kit/prod_3019.html

True,

of course in order for a leak down to tell you anything, you need to make sure nothing else is leaking

THis will require you to do a pretty good tear down (removing the generator and right side case cover to get to the outer seals, check the intake, base gaskets, head gaskets, etc..). If nothing else is leaking and you are loosing air from both cylinders, then it's probably the center seal.

I am thinking you could hook up a gauge to each side, set on to say 9 psi and the other to say 5 psi and if they start to equalize then you know you have a bad seal in the middle.

Andy's method will work as well, but not sure if there would be enough pressure to tell you of a seal that is just starting to go bad.
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Charles Gallant