CRF250 build - Motor too little?? Thoughts??

[Billy Golightly]

I'm not trying to discourage anyone but from what I've seen at a reliability standpoint these 250fs are SERIOUSLY lacking. The guys that practice a lot and race occasionally down here are getting about 4-5 months out of them before they need about $900 worth of work.

[atctim]

I have seen just the opposite from what Billy is saying. There was a Yammi 250 that was passed around between about 4 of my friends. It must have seriously had about 3000 hours on it before the engine let loose. upon tearing it apart - valves and piston and sleeve were all perfect. Crank bearings needed replaced.

I would not think twice about doing up a 250. But if you are gonna use a Honda powerplant - upgrade the valves. yammi seems to have the 250 motors down perfect!

[Jason Hall]

I put a crf250r engine In a 87 TRX250r frame for my boy, and It friggin RIPPPS. It didn't take much modding to the frame In the trx, but the atc frame would be MUCH mor difficult. The lower frame would have to be modded like Gordon (250Rfan) did on his 450 3 wheeler. It can for sure be done, as 250rfan proved, but would depend on how bad you wanted to do It. The CRF250 engine pulls the quad around great. My engine Is bone stock, the only place I feel like It needs more power Is when you roll on the gas In like 3rd or 4th gear with me on It. With my boy on It, It pull just fine. I have seen on Thumper Talk where they get up to 45HP out of the crf250r & YZ250f. Torque Is where the small engine would suffer compaired to the 450r.

Here's a few pic's of my trx/crf250

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[Jason Hall]

The biggest problem with all the Honda crf engine's Is the valve's. I put Kibble White's In my 450 and had Ron Hamp here In Michigan cut the valve seats. My 450 has been rode VERY hard, and I have yet to re shimm the valve's since I replaced them. I put stock titanium valve's In the crf250 and have adjusted them twice In about 3 hours of ride time. Yamaha has a MUCH better 4 stroke engine hands down, this Is coming from a guy that loves his Hondas. The Yamaha does not eat valve's like the Honda. If you keep the air filter extremely clean & change the oil very often you will save LOTS of money on the new 4 stroke's. My CRF450 still has the origional crank and cylinder, but I did change the piston when I first bought the engine. I beat my 450 at the dune's In Glammis / Gordons Well In California for 4 days straight & was very Impressed with how It held up. We rode for 20 mile's with one stop at full speed riding from Gordons to Glammis on the sand Highway. I did change the oil twice In those 4 days thought LOL.

[SeaBass8]

Service Honda sells new motors w/ electronics

http://www.servicehonda.com/parts/engines.html

How about the crf250 motor in the 2nd gen 200x frame?

[jeddy]

If it were me (and I've really thought of doing this myself, but am currently working on a Tri-Z), I would go with the WR250f (get an '03 or up to get electric start) and drop in a big bore. I've had a YZ250f and a WR250f (and a CRF450), and I can say the YZ really is a lot snappier than the WR, but tends to get hot a lot quicker. You can put the YZ parts on the WR to make it the same, but you might have some cooling issues. Check out http://www.thumperfaq.com/ for some good info about the Yamahas. You should be able to find a decent '03 or newer WR250f for under $2k with some scouring on craigslist. If you can figure out the kicker, you should be able to score a YZ for around $1.5k. The early bikes are good but they did improve them. My advice, if you get an '02 or older, get the newer exhaust cam with the auto decompressor. I'm not shy about kicking a bike (I also ride a KX500), but my '03 WR starts amazingly easier than my '02 YZ due to the cam. I know they sell kits to add a kick starter to the YFZ450 four wheelers, so I wonder if there's any chance you could put that in the 250f to get it to kick forwards? I'd recommend sticking to the 250R frame, but I don't have any experience riding one of the AF trikes. My 600X trike has some really poor geometry though (XR600 frame, terrible rake and really high seating position) and I wish I'd have worked it out on a 350X frame. For my 400ex powered 350x that's coming up (already have a donor 400ex, just looking for a cheap 350X), my main goal is to use the standard 350X frame to keep the good handling characteristics. Good luck, should be a great build.

[Dirtcrasher]

My thoughts were to drop it in an 86 250R chassis and make up some tripples and inverts down the road...

I too haven't heard the best about the Honda but people rave about the Yamaha powerplant.

Of course the 450 motor would be great but I tend to use all the power a motor has and I think I'll get into trouble with a 450. Whereas a 250 with some work I think might be perfect for me. It's a cautious balance between enough and TOO much....

I know I can't compare a dirtbike, but my buds KFX250 seemed to rip real well when I rode it and thats what gave me this idea in the 1st place.....

Thanks for all the opinions guys and Bigbore, I am 206lbs today.... This fluctuates between 190 and 220lbs though I gotta get running again this spring....

[Billy Golightly]

I think the difference between the longevity here and elsewhere maybe is that we are for the most part ALL sand. 99% of the mx tracks are all sand. And that means they have to be wound out constantly to keep moving...so maybe by necessity they are ran a bit harder down here then elsewhere but I've seen it consistently with all of the 250s, mosty the Suzuki's and Kawasaki's but just about equal were the Hondas and Yamahas

[Jason Hall]

That could be Billy, keeping them bouncing off the rev limiter would make for more rapid wear. I'm just a bit Pissed at Honda for not upgrading the Intake valve material. I have read alot about the seat velocity of these engine's, and the Hondas valve's seem to hit the seats harder than the others. Alot of that has to do with the down side of the cam lobe. Stainless Intakes are the answer, but does rob some HP, but In a 3 wheeler I don't think that little bit would matter.

I think the 4 stroke 250 would be sweet In a 3 wheeler. I hope someone does It soon.

[Derrick Adams]

Time for my opinion.
I think the 250 would be a potent machine in the hands of a light rider. At 200lb, I would not even consider a 250 for a trail machine anymore. We originally planned on a 250 for my Tri-Z, but the cost of the 250 is equal to the 450 and you have half the torque. After we went with the 450 I was so glad we did.
We also planned and researched a 250 this year for a small bore quad, however the price still isnt supportive. It will take $1700 minimum to build a rowdy 250 and in the end it will need frequent service.

Furthermore, neither of these engines will fit in a 250R frame without modifying it to the point that its not even a 250R anymore. Only 2 have tried it. One failed and the other is not ridden.

Lastly, if your dead set on a 250, then I would suggest using the 86-87 200X chassis. I believe it will fit better and is proportionally right for that engine. That chassis is well built too. Take a close look and you will see its built better than the 250R. But then again, at 200lb, will you fit comfortable on a 200X?

Just my opinion.

[Kintore]

That all makes great sense to me.

The more I think about it, the more I think that a 450 is the way to go. Not sayin a 250 is bad in ANY way. Just for the same price you can have more power/torque and beat the motor way less to get the same power. Now Im just thinkin a modded 250 will probably beat a stock 450 but at what expense?

I think if I was to do it, it would go in a 250r frame no matter how much screwin around. I think a X frame would be a lil small for me.

All depends what floats your boat I suppose

[300rman]

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

ever ridden a 125? you would understand why....light as a feather, and haul serious ASS.

[NOS_350X]

I dont think you guys give the 250f's enough credit.

I personaly doing think the 2 stroke 250's could hang with it. They have alot of low end power and rev to the moon and then go a bit more. I got 2 01 wr250f's and 1 03 yz150f in my shop right now, none have had any topend rebuilds. I think the weight of the 250 over the 450 would even things out, Its going to be lighter and easyer to thow around.

Stock 250f has mid 30's hp, Stock quads 450 are in the high 30's. 450 bikes are just shy of 50 hp. With work the 250f's can easely be taken into the high 40's some are getting 50 hp. Not too shabby.

[factoryX]

crf250r stock hp is under 30hp. then gets above 30hp with a fmf pipe...lmao.... here are the dyno test's from dirtrider.com. I kow why they did it to, more traction during take off...
http://www.dirtrider.com/141_0406_retraction/index.html

hp with different pipes:
http://www.dirtrider.com/141_0406_re.../photo_14.html

I think it lame that they have to build a 250cc 4 stroke to win a race over a 125cc two stroke, I mean put a CR250cc 2stoke vs. a crf250cc and it would be out matched.... this shows how the nation is influenced by morons that have to build a bike with twice the bore to compete with a 125cc 2 stroke...Or even this, how about a 450cc 2 stroke vs a 450cc 4 stroke???

I bet half the people riding crf250's where hop on a 06 cr250, the would eat it under a min. .

[BigGreenMachine]

That 250RF makes me happy. Wonder when Honda is going to mass produce one with a 250f in it?