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Tuning of an RD 250 / 350 two-stroke engine '73-'86

Last changes

9. Dez. 2016

Tuning RD 350 YPVS

19. Nov. 2016

15% Boost by the modification of the piston RD350 Air


18. Nov. 2016

Strong cooling effect by a small hole in in the piston  of the  RD350 Air

Hello fans of the air-cooled Yamaha RD 250/350. This homepage intends to find out how much a RD250/350 engines may perform. 
Any measures presented has been tested.


The website is still growing as I continue in my experience. I reflect everything as exactly as possible. But be aware that on this home page we try to touch technical limits of the RD engine. When reconstructing the tips you can easily go too far and ruined the engine, for what I am not responsible, of course. 

I run this site to find a few like-minded people. I do not sell anything and have no business interests with this website. Contact me via email, use the form or discuss with me on . I look forward to suggestions and will reply.


Do not start to widen the intake and exhaust port at first. Of all the measures I have tried, these have shown the smallest effect (+ 5%).
This is the list of successful modifications:

  • + 8%: Change of the combustion chamber shape in the cylinder head
  • + 10%: Change of the air filter with correct adjustment of the carburetor
  • + 15%: Changes to piston and cylinder foot
  • + 20%: Racing exhaust (Only recommended for water-cooled models. For the air coolers, the lead weights will  flying out.

If that is not enough

  • Larger outlet channel <5%
  • VForce membrane <5%
  • Digital ignition <5%

Please take into account that the so modified engine is thought for classic racing on the racetracks. Each bears the responsibility for themselves, in which chassis he inserts the resulting racing engine. However, should anyone come up with the idea to make one of the described modifications to a vehicle that is to be moved on public roads, so check, if you need a technical acceptance of the modification by an authorized authority.