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Rm 250 top end rebuild

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Hi I'm new to rebuilding bikes in general but I've just removed the cylinder head to get to my piston as my bike had really low compression and I found that it's not in the best condition an seems to be filled with water inside. I assume this obviously isn't normal I'll post some pictures as soon as possible thank you.

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The cylinder base gasket looks to be homemade from a cereal packet or similar. The water / coolant you are seeing in the crankcase does not appear to have been in there long as there is little sign of corrosion. Most likely it got in there as the cylinder was removed from the crankcase.

 

That piston certainly appears to be well passed it's best. Better have a good inspection and measure of the cylinder bore to check it's condition, and if it is usable select the correct grade of piston. Pistons often come in various grade sizes to ensure they fit with the appropriate clearance in a cylinder as it wears through it's life.

Also check the powervalve components too.

 

Installing a new top end on an unknown bottom end is a gamble and is not be a wise move. If there is any debris in the crankcase or wear in the crankshaft and bearings they could fail and damage the newly installed top end.

 

In the meantime it would be a good idea to flush out the bottom end a few times as soon as possible with something like diesel to get rid of the moisture before it starts to cause corrosion.

Edited by rmxdan

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