Because I can't get enough info to know for sure if the atv motors will bolt up and not have any differences I've decided to have it rebuilt. I was thinking I would possibly go up to a 700. From what I've read on the earlier years you needed to have the cases bored out so that a 700 jug would fit in. Then you would just buy a 700 piston and you're good to go. I don't know if I want to go that route but was thinking I could probably just have my 650 jug bored out and then re-nickled to a 700. Speedwrerx offers a 700 big bore kit for a 650 and thats more than likely what they are doing. I think I read today that the bore was 5mm bigger. If the machine shop doing the work is ok with this would that still leave enough cylinder to run at normal temps or possibly get to hot?