Already have a 103 kit, ported heads, cut .05, se251 cams. 106hp / 122tq. Wanting to upgrade to either 107 10.25.1 comp. pistons, 58mm se throttle body, bigger valves. Question is a 107 bore to big for the oem cylinders? And should i stay with the 103 and just go with more compression and the 58mm throttle body and what size vales should i go with?

 

Son, it's sounds like you have a problem....LOL

Welcome to the forum and the addiction.

 

Might check out site sponsor Fuel Moto and his new 107 kit. Welcome and Good Luck!

 

I can't believe I'm saying this BUT -- if the bike is running good leave it alone; the gains from a 106/107 are not going to be that significant over what you have now.

To answer your question of 107 bore to big for the oem cylinders? NO--I have logged more that 20k miles on a 107 not one problem--if you want an increase in power that you can feel may have to go 113/114/116/117 or my favorite 124

 

At 106/122, you're at about the max you should run with a stock bottom end. If you really want more performance than that, you need to pull the motor and build it up starting with the crank. Then you can bore the cases and go to a 117 or larger.

 

I would leave it alone

 

exactly what I mean --

 

I'm convinced. I'll keep the 103 but still will go to more compression and the 58mm se throttle body. Question is what size valves. 1.9Int / 1.615Exh or 2.1 int / 1.625 exh.?
Definetly don't want to stay with stock size valves. And to respond to first thread, 'You can never have enough power' not ready to go bigger where i have to bore cases. Would rather buy a big motor instead.