Hello to all!

I just bought an MC18 R5, I new in this forum and I just want to get facts and opinions. The bike looks godd and it starts after one kick, it has a lot of power and it runs fine but when I open the cylinder head and decarbonize the head and the top of the piston, I notice that there is a gap in betweent the piston and the cylinder. more like a clearance or play. when I tried to shake the piston using my fingers, it moved, not to big but a slight movement, more like a play? is this normal or my bike is messed up. I know that 4 stroke has a very small clearance, the piston is so tight inside the cylinder but I dont know about two strokes.

thanks to all.

can anybody give me some opinion, like when they clean their cylinder heads and touch their pistons? come on guys pls.

Both two and 4 stroke pistons can be moved. Std clearance is around 0.035~0.04mm on the NSR's, I'm sure the service limit is somewhere on site but I can't find it, I'd guess around 0.05mm, I've seen Matt advise 0.045 clearance on racebikes to avoid nipping up on long straights.

I never clean my cylinder heads or "touch" my pistons if I can avoid it

If it runs fine and the top of the piston looks like the perfect one here http://www.apexleisure.co.uk/pistondiagnosis.htm I'd just run it and enjoy it.
Re ring it every couple of years by all means as ringwear is high on all two strokes and clean the powervalves etc. but if the jetting is right they're no less reliable than anything else.

All of us idiots only seize them up so much as we keep jetting them too lean.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

There needs to be some play to allow for piston and cylinder expansion at running temp. Two strokes are no different to four in that respect, but they do generate more heat since they fire every stroke!

Do a compression check on the engine, and so long as both barrels read about 120psi then they're fine.
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