250 Motorcycle Engines

[tpotts]

Any comments on what 250cc engines (push rod or overhead cam) have had the greatest success, or the greatest potential for bike records would be appreciated.   Also what are some other sources for such information.  tx tom

[Jonny Hotnuts]

Forget valves

RG 250 Gamma.....

Just about 50 HP stock, and plenty of room, you wont find anything out there making this sort of HP for a 250.
(this would mean that a 1000cc motor would be making 200 HP stock!!). 

If I were to do a 250 this would be it.


.....no push rods or OHCs.

If you were dead set on a 4 stroke the ZX 250 is a good choice.

-JH

[tpotts]

Interesting reply Jonny, I recently obtained a  like new 2006 250 ninja.  Although I have owned a v65 magna and a VFR, this bike has really got me excited about 250cc and how much fun one might have with an engine this size.   From your view I assume that starting with what I have might be a good idea.   I am  also going to research the Suzuki RG250.  Thanks

[Jonny Hotnuts]

Landracings own SSS has the worlds only turbo charged Ninja 250. He alone likely has a bunch of knowledge on making in that bike.

I will say that in the smaller displacement classes I feel you will have a huge disadvantage to 2 strokes of like displacement.

Unfortunately the Europe-only bikes have a host of 250cc displacement machines that are way beyond what we can use here.

One of my choices if Europe bikes were legal would be a 250cc 2 stroke Aprilla.

Too bad, dont even want to think about it!


Good luck.....

Also you will see a lot of yamaha records in the 250 class....they are basically the same as the RG 250 but is known as the RZ 250 Yamaha....(almost the same bike).

[Roadsters.com]

The Suzuki RG250 Gamma was produced from 1983 to 1987.

There may be more of them in Canada than the US.

Here's an article about their history: http://www.suzukicycles.org/RG-series/RG250-Gamma.shtml

Dave
http://www.roadsters.com/

[mj43]

If you are going after a 250 production record I would use the Kawasaki 250 KR-1S (same as in my piccy) as off the shelf it is the best package. I ran a best of 137mph (136.5mph two way average) on mine in 2007and I think it has potential to go over 140mph; I didn't have the correct gearing .
There are a few in the states but of all the two strokes these, in the US, are probably the rarest.
If you can find one the KR-1R is the daddy however not sure they ever made 500 of them.

Of the other two strokes all are held back by the expansions. On the KR-1S Kawasaki did such a good job with the expansion no aftermarket pipe could beat the stock pipe. Not the case with all the other 250 strokers where to get the best out of them you need to fit after market kit.

The Suzuki RGV VJ22 and VJ21 are held back by the design of the expansions and to a lesser extent so is the Aprilia RS250 (same engine as the RGV250).
The Suzuki RGV VJ23 is probably a better bet - Japanese models were restricted to 45hp (as were most 250 and 400cc machines) but a full power version was exported again it is the standard expansions that limit them.
The Yamaha 3XV which is basically a TZ250 is the best of the Yams but again the standard exhausts hold it back.
The Honda NSR250 MC28 or 21 are the best Hondas to go for but again I think the stock expansions limit them.

The four stroke 250's will never match the two strokes, they are down on power, heavier and have a larger frontal area.

Info on the RGVhttp://www.rgv250.co.uk/
Info on the NSRhttp://www.nsr-world.com/

[kiwi]

If you are not going for Production class the 250 GP engines would be good. The older ones being the Yamaha TZ, and Rotax made a tandem twin. The late model Honda GP engine also make lots of power, though more expensive than the older stuff.