Thumper Racing's XR650L 675CC Big Bore Kit Questions.

good work zac keep us up to date

Thanks everyone! I think im gonna have to do something else, it still needs more power. Especially for the new 17's I'll be gettin on there soon. I think oversized valves and a pumper carb is the next step, maybe a higher lifting longer duratin cam too... What else is there to do besides all this? Thanks


I run a Wiesco 10.25:1 piston (standard bore) with a full port job and Hotcams stage 1. The valves are stock with stock springs. I run a Yosh full exhaust and a Edelbrock pumper. Runs fine on 93 gas by the way.

I can tell you that the port job and cam destroyed the low end torque. The engine now loves the mid range and top end. The thing will pull your arms off if you let it rev up. Very similar to the uncorked XR650R my friend has.

The stock carb sucks for the modified engines, I could not tune it for my engine config. The Edelbrock is awsome, much better response and power thru out the rev range. I would say my bike has 50ish Hp, to get much more you need to spend alot of money.


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