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power with reliability
piston top Thumper Racing's been building big bore machines for your 4 stroke for many years. We're no stranger to the podium, endurance racing, or just impressing your buddies. Want it done right, call us . . .
do it right with our top end kits
big bore quad on 24 hour endurance race
fmf carbon slipons

We've been around the Big Bore Four Stroke industry for awhile now and have seen them come and go. Our kits and components have all undergone extensive torture test in the real world with real customers, real racing, real endurance riding, and we have fed that back into our kits.

You can experiment yourself on your expensive thumper four stroke, but when you want Big Bore Power that "Just Works" and won't leave you stranded, make your ride impossible to start, or give you power that's unpredictable and "peaky", give us a call.

We are under heavy development for packing more power into smaller motors, like our KTM 250+ big bore kit, which pumps up your motor to a 320cc screamer, but with more power comes the need for more cooling, so we re-designed the cylinder kit to get 15-40% more cooling for a more stable core cylinder temperature. You can read more about our KTM 250+ big bore technology here

 

ktm big bore kit
ktm 250 to 320 big bore kit
Call: 661.424.1800
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