350 big bore kit for all years and models of TTR250 inc. the Raid

Product no.: TTR-0868

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Price incl. VAT,

350 big bore kit for all years and models of TTR250 inc. the Raid.  

Your kit will include piston kit, new barrel with liner fitted already bored and honed for the new piston, and a head and base gasket set.

Please email sales@totallyttrs.com if you are interested in buying a kit. 

  • A genuine 346cc – nearly a 100cc increase! The Thumper Racing 325 kit is actually only 315cc.
  • Newly cast barrel so you can sell your old one to help fund the kit! 
  • The barrel has a thicker wall than the original so that, when bored to take the sleeve, it still has plenty of meat left. No oil weeps through cracks in the barrel as has happened to quite a few owners who have used the Thumper Racing 325 kit.

  • New liner/sleeve with sufficient meat on it to allow for rebores if ever needed in the future.

  • Quality Wossner pistons (made especially for the kit) together with excellent Cometic gaskets are supplied in the kit.

  • The only machining work needed by the customer is to bore the crankcases to take the bigger sleeve. Most engineering workshops can do this and it’s not expensive. Circa £30 to £40 in the UK.

  • No need to modify the cylinder had or other parts although owners are welcome to improve the airflow by modifying the airbox, gas flowing the head, using modified camshafts with different lift and profiles, free-flow exhausts, shorty headers, larger bore flat slide carbs, etc.  Feedback on any such mods will always be appreciated vial the TTR250 forum.


Now only available by email order.




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