Zman
Platinum Level Site Supporter
I am rebuilding a 2001 XC250 engine I bought off the classified section last year. The top end is worn out, looks like insufficient premix oil. I found it had a badly worn 86-96 Honda CR250 Namura piston and the rings had a 6mm gap
. The lower connecting rod bearing was a little sloppy too so I am doing a full rebuild. Ryan Callies http://www.finishlineengines.com/ was able to clean up the cylinder with a his diamond hone and he is rebuilding the crank for me too.
Because of the cylinder wear, we needed to hone it more than normal so it needed a slightly larger piston for the bigger bore. I started looking for another Honda CR250 pistons and while searching on the Wiseco website I found that a 96-97 Suzuki RM250 (Wiseco 681M66040) piston is a cross over for the 86-96 Honda CR250 piston. I found a new RM250 Wiseco forged piston kit on ebay for $50. It measures 66.38mm and should work great with this 66.405 cylinder.
There are some differences in the piston skirt design but I have a similar skirt design in the 76mm ATC250 bigbore piston we used in my XC300 and it works great. I should have it together in a few weeks. The RM piston is slightly heavier than the stock Wiseco but then again so are the Wossners. The photos show the new RM250 piston next to a used EC250 Wiseco piston.
. The lower connecting rod bearing was a little sloppy too so I am doing a full rebuild. Ryan Callies http://www.finishlineengines.com/ was able to clean up the cylinder with a his diamond hone and he is rebuilding the crank for me too. Because of the cylinder wear, we needed to hone it more than normal so it needed a slightly larger piston for the bigger bore. I started looking for another Honda CR250 pistons and while searching on the Wiseco website I found that a 96-97 Suzuki RM250 (Wiseco 681M66040) piston is a cross over for the 86-96 Honda CR250 piston. I found a new RM250 Wiseco forged piston kit on ebay for $50. It measures 66.38mm and should work great with this 66.405 cylinder.
There are some differences in the piston skirt design but I have a similar skirt design in the 76mm ATC250 bigbore piston we used in my XC300 and it works great. I should have it together in a few weeks. The RM piston is slightly heavier than the stock Wiseco but then again so are the Wossners. The photos show the new RM250 piston next to a used EC250 Wiseco piston.
