This is going to be a silly question as I know motocross engines are designed to behave much differently from our dual sports... buuuttt...

I had the fortune of riding a couple other bikes this weekend:

2003 KDX 220 2 stroke

2005 RM450Z 4 stroke

2013 CRF250R 4 stroke


All these bikes were fun in their own way. The 450 was a ton of work to ride, not fun for a novice like me... scary actually.

The KDX220 had the worst suspension I've ever ridden on, but damn the powerband on that 2 stroke engine was a blast in the trails. Power wheelies in second gear, and 3'rd with some assistance.

The CRF250R was what I wished our engine was. Tons of bark down low and a nice smooth middle to top end such that I wasn't scaring myself like I was on the 450.

So my question is this, for anyone who's ridden these bikes or something similar... Is it possible for our little dual sport to behave in anyway similar to these engines in terms of power?

The cr250R is about 35hp stock and I've heard the 351 BB kit will net you about that, would the performance be similar or is our motor going to be void of that addictive low end snap power that's so fun on the 250r?

I have to say also, after riding all these bikes, I have a whole new respect for the suspension on the KLX250s. Yea it's soft... but it's actually quite good. It doesn't beat the snot out of you like a MX suspension, and the compression / rebound dampening is entirely respectable.

 

Well the answer is "kinda"... There is no data showing a 351 making 35 or more HP. It does look as though 30hp is attainable without resorting to custom port and valve work - but this requires a BB kit, carb, cams, and exhaust - almost $2000.00 - but with a powerband that should feel similar to the CRF .... Subtract the $436.00 cams and you get 28hp with power that tapers off quicker in the upper RPM's than with the cams ...

 

I don't think any amount of money could build a reliable 250s making 35hp. As a general rule; add power, square wear.
What you want is a ktm exc, husqvarna te, beta rr, etc. these are true dirt bikes, street legal from the factory. You can plate dirt bikes in certain areas, so that may be an option.

 

ahah, yea, I don't suppose you've got 13,000 dollars and a shop I can have?

I know what want, but I also know what I have and what I can work with. I was just wondering if an upgraded klx250 with a 351 BB and mikuni is anywhere near the crf250r I rode.

 

It would be a really fun bike, but it won't feel as nimble and snappy as the CRF. Before you start dumping money into your KLX, I would look into getting a quick-throw throttle. Sometimes bikes feel a lot quicker just because when you barely open the throttle they snap quick. Doesn't mean they are any better for trail riding though.

BTW, I have a tagged KTM 250 XCFW. The suspension and top end power is awesome! But I would never trade my old KLX300 for it.