Hey guys

back with another issue. i've put my bike back together with a new top end, and she runs well now. Only problem is after running for a minute or two coolant starts coming up around the cylinder base bolt/nut below the power valve on the top cylinder. I hadn't done it up tight enough initially ( ) but it's now tightened up as much as i can wil the limited space i have. i can't get my torque wrench/socket on that nut thanks to the valve assembly.

any ideas why its still leaking? Could there be coolant getting into the crank??

I had this very same problem with the MC21F3. Turned out to be the base gasket. I took the cyclinder off, looked at the old gasket (which was new) and couldn't fault it. Replaced it and the leak stopped.
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If I have to take the carbs off once more...

hello again

Thanks for the advice, i'm going to have a look at replacing the base gasket

Started to take it apart, and noticed that the nut on the leaking bolt has a groved bottom. Could that have cause the problem? I think i must have put the wrong one on when doing it up

the one on the left is the one that was on the leaking bolt, the one on the right is what was on the other 3 bolts

no mate it will be the base gasket

That left nut is a crude locking device, designed to prevent the nut loosening. Trouble is, on soft alloy it just tends to chew the metal up each time you remove it.
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bj wrote:Started to take it apart, and noticed that the nut on the leaking bolt has a groved bottom. Could that have cause the problem?

Well, it's not helping that's for sure, Honda used smooth bottomed nuts for a reason and no matter how you "torque" it up (wheather it's with a torque wrench or the more usual torque wrist) it'll end up different to the rest, add to that once they've leaked gaskets don't like sealing.
It's not like it's the world biggest job anyway so just change it, use a proper nut and double check the cylinder and crankcase faces are clean.
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