350cc conversion for EXC 250 Racing 4stroke

[trallali13]

Hi,

does anyone have information about the 350cc conversion kit for the 250 EXC racing 4 stroke? what is the normal horsepower for the 250 and what can be achieved with the 350 kit?

Thanks,

Georg

[mcdrz]

There are two different sources:

KTM has a factory 350cc kit. It is basically a 400CC top end to bolt on. I think it is around $800.00 See your dealer.

The second source is HT Racing. The kit is 351cc. Here's the link http://www.ht-racing.com/pages/1/index.htm

Hope this helps.

[OldeDude]

I believe that a stock 250 RFS is about 29 horses. HT Racing says that their 351 kit, with the head mods that they can do, will boost that up to about 42.

[Travis_D-37]

I've rode both the KTM 350 kit and the H-T racing kit and the H-T kit will smoke the stock KTM kit hands down. IF your going to spend the $ to make it a 350 get the better kit. This is the one time KTM parts are not as good as aftermarket.

[VCRider]

Just ordered the 351 kit from HT-Racing for my new (non-current) 2003 250 RFS, they are running a special that includes the cylinder (don't need to ship yours in for re-sleeving..), JE piston, gaskets, seals, and cam chain link - all for $599.00. This really is the only way to go. I don't advise on the KTM kit (topic discussed on KTMTlak site..)

Regards/Brad

[Dave Hopkins]

The HT kit has a piston made for the specific instalation, the KTM kit uses a piston for their parts shelves, (450sx??) The problem there is the piston was made for the head that used on 400-525 models but the head used was made for a 250 and has smaller valves closer together. Thus with the KTM kit the valve pockets are too big and in the wrong place, thus the compresion ratio is way too low. Using the big bike head is not the answer either as it has a bigger combustion chamber, again compresion too low. You need the made to suit piston of the HT-racing.com kit.

Everyone that has riden one came away very impressed. A side benifit is the gear ratios of the 250 are more trail rider friendly than that of the big bikes.