They(F4i) are 599, but equals out to 637cc on the F2. They are exactly the same specs as the wiseco and requires a 2mm big bore to your engine case. Look though my posts and you will find a lot of specs for the 637 big bore build on a budget.

 

so i could basically buy the f4i pistons and rings stock, and bore out the cylinder head.... or just replace the stock rings and re hone the cylinders.... I think stock is cheaper lol

 

Yes, stock is cheaper. I have seen on ebay brand new F4i piston(never used)NOS without rings for $20 and a big bore only costs $150. Now you would have to get the big bore .018 gasket for $82. But over all gain around 15 extra 'Hp'. Look for my 637 post for entire budget cost, I broke it down for everyone. You would have to use the F4i intake cam and use the F2 intake cam for the exhaust and use adjustable cam sprokets to get the nice 15-20hp numbers. Cheaper than going and getting a new bike that may be a little faster

 

Thanks for the info, Underground, I will be bookmarking your 637 build post, and referencing it when it comes time for a rebuild!! Or, when I score a cheap "extra" F2 motor!



And Jank, you are in a perfect situation to toy with this right now, and report back!

 

I just got my mom to help out (broke *** college student) so a shop is honing the cylinders for 15 a pop and the rings are 26 a set

 

im about to order my piston rings and they give you the option of standard .25 .50 and .75 what size would i need? im about to get the cylinders honed as well