CRF250 build - Motor too little?? Thoughts??

[Dirtcrasher]

Hey guys, I really want to put something together here shortly.

I've ridden both a 250 and 450 four stroke and although in time I'd probably settle in just fine with the 450, I think the 250 would be my choice of a powerplant.

Although it will have 2 wheels to spin and more weight, does anyone feel I would be completely unhappy with this size engine swap? I'm pretty happy with my 350X's power, I'd love more... But basically I'm looking for some better hill climbing ability (wheelspin ) and I certainly need to shave a bit of weight of while improving the suspension allot also..... Although I can dump 1000$ into a 350X motor and gain tons of torque, I'd still be limited to the 350X chassis and the heavy air cooled engine.

It seems the 250F motors have tons more useable power than the 350X and of course are lighter and can be stuffed into a better chassis.

I'm thinking about buying a complete CRF250 (04-06) and part it out keeping the electronics, motor and anything else I may need... People seem to want 1500$ plus just for a motor and with the economy the way it is, I think I can grab a complete machine for under 2500$ and lower that engine cost down a bit.

This would go into a 86 250R chassis with a 450R rear end and the front suspension would stay stock for a bit until I built some triples to accept some better forks.

I'm getting OLD but I do still ride HARD, but I don't think I ride hard enough for a 450 powerplant...... Remember, I'm not interested in a 250R motor, that "lightswitch" power is just not my style. I want controllable, useable power that can compliment a fresh and well built chassis.

I'd appreciate some thoughts from you all, esp the few of you that have completed some awesome conversions

[Kintore]

Hey, this has been thrown around the OTC guys for awhile now. Using a 250r frame (beefed), inverted front suspension, elka/axis/fox rear shock on a 450r alum swinger with a +4 axle.

Ideas are still up in the air, but my idea would be a modded out 250f motor would haul some ass for sure, but why not roll to a crf450 motor and use it? Your there might as well go big or go home right? Im still debating which I would build/buy to be honest. The 250f hasnt been done to my knowledge, the 450 has but might as well use the bigger displacment if its available. Although the 250f motor is cheaper.

[sandpuppi101]

I personaly think that a crf 250 conversion would be a nice build.I mite suggest that instead of you using an existing 250R frame and modding it that you get a bit more innovative and use the crf frame as a canvas for the build.Just remember if you want it bad enough it'll happen..Good luck with your project..

[WaimakRydah]

Ive heard that doing the pistons on a CRF250R costs like $900(NZ$ dont know what that would be in USA$) including mechanical labour as theres all the valves to deal with which you dont have on a 2 stroke. Ive ridden an 08 YZF250 and its got pretty much a perfect amount of power and a nice powerband but at $900 I couldnt afford it at the moment. Especially considering its more then what my whole trike is worth.

[tecat-z]

WR 250f powerplant. Lots of pulling power, wider ratio trans will allow deeper gearing for acceleration due to added weight, but still retain top end snap. Plus the magic E-start button. No messin around tryin' to get the kick start to fit. And no hot start issues. I think a 250 r based chassis would prolly be best for this as well. Would be a sweet trike no doubt! And a real terror on a MX track.

[WaimakRydah]

Whats the WR250F like compared to the CRF250R

[tecat-z]

You would have to compare it to a crf250x. Fast, high revving, and e-start. Both good choices.

[300rman]

i would go with the 450. they seem to hold together better, and if you rode the 250 and 450 the same, the 250 would be working harder than the 450 under the same conditions.

[OZQUAD44]

I can't comment on the power, but the size would be good.

Light weight and you should be able to fit it where the 250 two stroke used to fit without mauling the frame too badly.

A lot of these 450 conversions seem to take a lot of work to fit in there. The 250 four strokes seem to be more compact.

Plus if power was a drama, I know they do 300 kits

[zmpolaristech]

I think I would have to say that the 250F engine would be KILLER in a trike chassis of some sort. They make GOBS of power, they're lighter than a 450, and MUCH easier to cool (450's run VERY hot). the stock 250r rads would probably be more than sufficient. And i am sure it would outrun even a built 350x. If it were me building it, i think I would utilize the ALUMINUM crf frame w/some different triples and a custom swinger.

[maggiesboy]

I think a 250F powerplant of any make would be a killer trike. GO FOR IT!

[WaimakRydah]

People say the CRF250R/CR125 can out run a 400cc trail bike

[cr480r]

does anyone feel I would be completely unhappy with this size engine swap?

I know I would be unhappy with it... But I also weigh 200lbs and like all the grunt I can get.. I will say that I think it would be a cool swap and very fun to ride in the right situations.. How much do you weigh dirtcrasher? what kind of riding do you mostly do?

WR 250f powerplant. Lots of pulling power, wider ratio trans will allow deeper gearing for acceleration due to added weight, but still retain top end snap. Plus the magic E-start button. No messin around tryin' to get the kick start to fit. And no hot start issues. I think a 250 r based chassis would prolly be best for this as well. Would be a sweet trike no doubt! And a real terror on a MX track.

the WR250f that I rode was not impressive.. the huge gap between 2nd and 3rd gear would be garbage on a mx track.. especially in a trike

[fabiodriven]

I'd personally prefer the 450, but if you did the 250, that would still be cool either way. I'd have to figure the 250 would probly be in the ballpark of your 350X, except for the different manners of the more modern thumper.

[Kintore]

Bringin this back up, any more ideas/thoughts towards this?

Honestly contemplatin gettin rid of the 265 Duncan PV setup in favour for a nicly built 05+ crf250 setup, like piston, cam, exhaust...

what kinda numbers these push out stock and modded?