Rebuilding Motor

[freebyrd24]

I have a 1977 Suzuki RM250 motor and a 1980 rm250 head. Now I'm trying to reinstall the piston in the head and am having some serious problems. are there any tricks, techniques, or special tools for this? I had my friend over who rebuilt his 2 stroke many times without problems. and we just struggled today. from the bottom i can get the piston started but after about an inch it doesnt wanna continue, and the cylinder walls r clean. any ideas?

[2002shee]

Once the rings clear the sleeve it should be smooth sailing. Sounds like the cylinder may be tapered. Try measuring using an inside micrometer or dial indicator. Are you trying to put it together with the head bolted on in which case compression will get in the way.

[holtzer1]

take the piston off the rod, see if you can install the piston by hand all the way into the cylinder...its easier to do this way beings your already having problems. it does sound like the cylinders tapered....is it a fresh bore/piston?

[MX86]

take the rings off and see if the piston catches...

[Kane]

Right, remove the rings and then try. If it doesnt have any problems then, you need to chamfer the ports a hair as the rings are likely catching on a sharp port edge.

[freebyrd24]

i took the rings off and tried it and it still caught. ive been trying with the piston disconnected from the rod. its an old piston and bore. yes i had the head attached still. could compression really be that good tho? ill try it without the head on, but any other suggestions if that wont slide on?

[freebyrd24]

thinkin on the drive to work, the plug was not in the head. wouldnt this allow for very little compression?

[yamahamotocrosser40]

you would still be having a hard time getting the piston on i would take off the head has the cylinder been rebored because if it has no i would agree with the other guys that it has a taper in the cylinder or is catching a port and if you tried it with out the rings then i would try to take off the head and try it and if that does not work than you probrably have a tapered cylinder

[freebyrd24]

cylinder has not been rebored to my knowledge. ill try to take the head off, if that doesnt work ill probably have it bored

[freebyrd24]

just to let everyone know, the 1980 head will NOT bolt up to the 77 block, completey different. the 77-78 are alike i believe, and so are the 79-80. also the piston was 20 over.