CRF250 build - Motor too little?? Thoughts?? [Archive]

Dirtcrasher

08-26-2008, 08:27 PM

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 :D 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

08-26-2008, 08:45 PM

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

08-26-2008, 08:48 PM

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

08-28-2008, 09:40 PM

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

08-28-2008, 10:08 PM

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

08-28-2008, 10:24 PM

Whats the WR250F like compared to the CRF250R

tecat-z

08-28-2008, 11:51 PM

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

300rman

08-29-2008, 12:27 AM

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

08-29-2008, 09:31 AM

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

08-29-2008, 09:42 AM

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. :w00t:

maggiesboy

08-29-2008, 08:51 PM

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

WaimakRydah

08-29-2008, 09:46 PM

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

cr480r

08-31-2008, 04:48 PM

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

08-31-2008, 09:49 PM

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

01-15-2009, 09:40 AM

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?

Billy Golightly

01-15-2009, 10:04 AM

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

01-15-2009, 02:56 PM

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

01-15-2009, 03:22 PM

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

http://http://i237.photobucket.com/albums/ff42/Jasons450r/crf250done005.jpg

http://http://i237.photobucket.com/albums/ff42/Jasons450r/crf250done002.jpg

http://http://i237.photobucket.com/albums/ff42/Jasons450r/trx250f3.jpg

http://http://i237.photobucket.com/albums/ff42/Jasons450r/trx250f5.jpg

http://http://i237.photobucket.com/albums/ff42/Jasons450r/trx250f.jpg

Jason Hall

01-15-2009, 03:37 PM

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

01-15-2009, 05:16 PM

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

01-15-2009, 10:07 PM

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

01-16-2009, 01:05 PM

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 :lol: I gotta get running again this spring....

Billy Golightly

01-16-2009, 08:01 PM

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

01-18-2009, 04:36 PM

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

01-18-2009, 05:57 PM

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

01-19-2009, 09:32 AM

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

01-26-2009, 11:55 AM

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

02-08-2009, 12:45 PM

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

02-09-2009, 03:54 AM

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_retraction/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

02-17-2009, 12:26 AM

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

Kintore

04-21-2009, 08:53 AM

Anymore intake on this guys?

This might just be my winter project.....

but so far what ive read on forums/forums here the yami 250 is the ticket,
Is it wrong to have a yami 250 in a 250r?

Or build it off the bike frame?

atctim

04-21-2009, 08:56 AM

slap that yammi motor right in that honda chassis you slappy wag!

Best of both worlds pal. No screwing around with bike conversions!

Dirtcrasher

04-21-2009, 10:33 PM

I can't attempt it any time soon :( but I'll get there someday.

We have to update our old crap sooner or later......

I just tore down a Kawi 250F for a friend in need of a top end and that thing is chicken. I thought it would be something special, but there is nothing to be afraid of with these simple motors.....

But, until I hear good stuff about Honda, I won't be using one and that REALLY makes me ANGRY!!!!!!!!

Kintore

04-22-2009, 07:33 PM

Same here DC, dont seem right to shove a yami motor in a honda does it?

sshhhh ill grind them polish out the sidecases if I gotta!

Kintore

04-26-2009, 12:21 PM

Honda motors NEW with carb and elec are gettin CHEAP!
http://cgi.ebay.com/ebaymotors/05-CRF250R-ENGINE-05-250R-ENGINE-05-CR250F-ENGINE_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1171Q7c66Q 3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a0Q7c29 3Q3a2Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZi tem120410296175QQitemZ120410296175QQptZMotorcycles Q5fPartsQ5fAccessories

SeaBass8

04-26-2009, 12:30 PM

Is that Service Hondas Ebay store?

Billy Golightly

04-26-2009, 12:57 PM

Wow, relatively speaking, THAT IS cheap. If I had the extra dough laying around right now I'd buy one and do it.

Kintore

04-26-2009, 02:27 PM

think a stock motor will have the guts?

really thinking about selling the pv duncan motor for this.........

SeaBass8

04-26-2009, 05:27 PM

This is Service Honda engine page

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

factoryX

04-27-2009, 03:27 AM

think a stock motor will have the guts?

really thinking about selling the pv duncan motor for this.........

I would never do that..lol hp for hp is a complete joke...

Kintore

04-27-2009, 07:31 AM

Torque there bud, torque is the key.

Plus no one else has it, I would be the first!

Yamada

04-27-2009, 12:33 PM

Torque there bud, torque is the key.

Plus no one else has it, I would be the first!

Try to find some one with a 250F bike or go to your Honda dealer for a test ride. It would be a good way to see how fast they are.

factoryX

04-27-2009, 04:18 PM

lol torqe? that is why those motors go boom. The 250r motor will wipe the boards of the crf250 motor...lmao and last longer to...

Dirtcrasher

04-27-2009, 04:43 PM

^ I've got a fresh KAWI 250F here now and it pulls all the way thru every gear. From bottom end to top, it's all there. From dead nuts there are gobs of torque....

That is why I was interested in these motors in the 1st place, there is no "light switch" power there.

Kintore is allot younger than me and most likely very comfortable with a well built 2 stroke.

Myself, I want manageable power that won't get me in trouble and thats what happens when I ride a 2 stroke. I get in the meat of the power, crack 4 gears and I'm in the woods or on my back.

The 250F does not hit like that but revs to the moon like a 2 stroke when you want it to.....

Is the 250R motor awesome? YES; Do the last forever if built correctly or factory? YES. But, thats not the power I'm looking for......

Kintore

04-27-2009, 08:57 PM

lol torqe? that is why those motors go boom. The 250r motor will wipe the boards of the crf250 motor...lmao and last longer to...

The 250 will have more torque than the 250R motor. Even if it does go "boom".

Just because something is fast does not mean its ridable power. Im lookin for a small bore motor I can huck around in a R frame.

Thanks for the wonderfully helpful insight into this conversion :rolleyes:

outtaline

04-27-2009, 09:07 PM

Dirtcrasher

04-27-2009, 09:32 PM

^Junk, useless, going backwards, underpowered and outdated for a heavier trike etc etc etc.

BUT, to each there own :D

outtaline

04-27-2009, 09:38 PM

runs great picked up anyways even tho I don't like 2 wheelers I tend to hurt myself guess I'll sell it only paid 50 bucks

cr480r

04-27-2009, 09:54 PM

Not to get off track but how would a cr125 work in a 200x has anbody tried I can get one cheap I could pay for it selling parts Ive been gathering only downfall I can see is 2 stroke I like the crf250r idea

I think the CR125 in a 200x would be a great project for a lightweight rider that has a limited budget to work with...

lol torqe? that is why those motors go boom. The 250r motor will wipe the boards of the crf250 motor...lmao and last longer to...

true story... I think building a trike around a 250f engine could make a nice machine for certain people.. But why anyone would want to pull a functional 250R engine an replace it with anything less than a 450 is beyond me... There are cheaper ways to reduce HP and wheelspin than doin a complete engine swap...

outtaline

04-27-2009, 10:46 PM

I just might try this I only weigh 150

Bryan Raffa

05-02-2009, 10:22 PM

Dirtcrasher

05-05-2009, 05:42 PM

I'm in the process of dealing with a KXF250 and the motor is a POS.... I've heard NOTHING good about them. Bad tranny, improper and under cooling, valves in constant need of adjustment, bad cranks destroying cases, cam cap torquing seizing the cam etc etc.

The kid waits until I have it honed and install a new piston to tell me "the water pump wasn't working when I lost compression" :rolleyes: I had sent him off to the local Kawi dealer with the head and cylinder to be looked at and tested and they didn't find anything wrong but we have very little compression so there is obviously a problem. Now that I've been talking with people, I hear all bad stuff about the 04/05 KXF250.

He had initially asked me to replace the topend and adjust the valves just to "keep it fresh"

Everyone raves about the Yamaha's so when I build one it's gonna have a YZF powerplant :D and it's going in an 86 200X square frame.......

I won't be using a Honda motor unless I hear allot of good stuff about the later models......

torker

05-05-2009, 08:52 PM

I'm in the process of dealing with a KXF250 and the motor is a POS.... I've heard NOTHING good about them. Bad tranny, improper and under cooling, valves in constant need of adjustment, bad cranks destroying cases, cam cap torquing seizing the cam etc etc.

The kid waits until I have it honed and install a new piston to tell me "the water pump wasn't working when I lost compression" :rolleyes: I had sent him off to the local Kawi dealer with the head and cylinder to be looked at and tested and they didn't find anything wrong but we have very little compression so there is obviously a problem. Now that I've been talking with people, I hear all bad stuff about the 04/05 KXF250.

Everyone raves about the Yamaha's so when I build one it's gonna have a YZF powerplant :D and it's going in an 86 200X square frame.......

I won't be using a Honda motor unless I hear allot of good stuff about the later models......

That sounds sane. But a good suspension will help keep you out of touble to.
I don't think the 200X suspension can be compared to the R's. Can it?
Don't have a lot of feedback on the later 200X's.
TORKER.

Dirtcrasher

05-05-2009, 10:10 PM

^ Hey bud, no I won't be anywhere close to stock suspension. It's the boxed frame that would be the general skeleton but a 250R front end to start with and something with a linkage in the rear would be the least I'd run with.

Of course as I said before, it won't happen this year with my situation so it's thrown out there for you guys :D

Doesn't matter who or how it's done, as long as we head in that direction..........

willrideanythin

05-06-2009, 01:23 PM

My .02 is this. I have seen a CRF250 go very good with a little work. Just as fast as my Arctic Cat DVX434. Not to mention spanking people with a 250 4 stroke is fun when they run larger engines. You will still be lighter then a quad, and beating quads with trikes is what is all about. 250 4 stroke all the way.

devilman

10-17-2009, 07:08 PM

after reading this thread so i try it or not?

i have an 05 crf250r that i really don't care to ride. should i spend money to convert it? i have a rear end from 06 trx450r that i was going to put on my 85 R, that i could try to put on the bike. would the trans hold up?

someone offered to trade a 350x for the bike but i haven't received pics or any other word about it from them. scammer i bet

atcmanic350x

10-18-2009, 07:50 AM

this guy

10-23-2009, 01:44 AM

Good god what the hell is wrong with everyone. A Honda 250F?!?! For a while I was very involved at pala raceway(trike friendly) and I watched so many stupid 4 croaks explode everyday it was sickening. The only ones that stayed together were the newer single overhead cam KTMs(they are no mas, but easy to find used) and the Yamahas. The honda 450 is the only engine that I have seen a piston turn sideways in and launch trough the top of the head. Being a huge Zuki fan I hate saying it but the RMZ450s ran awesome till they completely come apart and that they do in spectacular fassion!! I don't have a whole lot of experience with the newest quad engines, but bikes I'm up to date on. Use a Yamaha(any motor YZF,YFZ, WR,250,400,426,450 they are all good) or the Can am 450 motor(nothing wrong with rotax).