ATC250R Motor ...

[Jeb]

Allot of you guys drop the CR500R motor into the 85/86 ATC250R chassis.

Any thoughts on dropping a CR250R motor into an 85 ATC250R chassis? You gain a power-valve and lose the counter-balancer. Pick up some more horse power and more vibration. But so what. It shouldn't vibrate any worse than a KXT.

Aside from the Internet sales or ebay, A man could shake the local trees and find a steal of deal on a mid or late 80's, maybe even early 90's CR250R that runs good, especially compared to the on-line prices of 250R ATV engines.

[86waterpumper]

One problem I see is that you gain not only the cr250's powervalve, but also it's tranny gearing. This could be overcome probably with regearing, but it's something to think about. Plus like on any bike you would have to deal with the kicker going backwards, but with some sidecase work, this could probably be gotten around. Red rider put the powervavle on his bike, and has a nice write up about it on his webpage.

[kdagenais]

I thought it would be interesting to see a 95 or later CR250 motor in a 250R chassis. Think of the gains you would have with a new genreation engine in a R.

[Jeb]

There I am thinking KXT! :oops: Too many years around them. They kick rearward so I wasn't even thinking about the forward kick of the ATC250R motor.

anybody make an electric start kit for a CR250R???? :D :D :D

[86waterpumper]

it still would be a cool project. The late model cr250 motors put out much more hp than the atc ones ever did. If I was going to fool with all the modifications, I would want to put a 95 or newer as kdagenais said. I guess noone around here has gotten a cr motor cheap enough yet to do one up.

[kdagenais]

Yea it would be a bit expensive and your best bet would be by a complete bike. You can find a 1995 to 1998 around $1500.00 which would be the way to go since you are going to need all the electronics etc. Then you still have to figure out how to handle the rear kick starter. Still would be interesting to see how the R would handle with the new engines. Its only a small matter of money, time & ingenuity.

[Dirtcrasher]

It's a great idea - my 94 CR250 had a nice smooth power delivery and lots of low end torque. My 85 ATC 250R is a lightswitch powerband and until I get some more miles on it - it is useless on my MX track. One mistake of that thumb throttle and I'm heading for a tree after overjumping something by 20 feet. In stock form for me it is not "friendly" maybe a pipe or something would help but it's really only hair raising fun on straight aways and difficult to time the leaps. However I do have very little time on this ATC and I'm sure it will get better.

I've seen people do the conversion and hinge the left rear fender so they can flip it up and kick it backwards. Hell of alot cheaper than a new idler gear and machining or an electric start,

[ChrisD]

How about the ESR330 motor. I just bought one. It is a complete bolt on kit with a new head, spacer plate, cylinder, gaskets and piston for $1000. You will need a long rod for your motor, but I already have one. You can also get the ESR310 kit for a little cheaper and don't need the long rod. Huge power gain with the counterbalancer, without rigging a pipe, without rigging the kickstarter etc. Not a bad deal.

JohnR bought an ESR330 last year and it was fast. On the ice, with 18" tires, he topped out at 95 MPH. He had me by about 10 mph. I don't know how fast they are on dirt or pavement, but 95 on the ice is awsome. The bike had tremendous power. I was very impressed. I can't wait to put it in.

The KXT is a good bike to transplant motors to. Another friend put an ATC250 motor into one just fine. Some motor mounts and he was all set. He's running a 300 kit on it.

[Aaron2003]

the way i figure it if i'm going to spend 100 to 1500 on a eng. i'm putting in a cr500 eng, in it which i'm in the process of doing as soon as i find a roller...

[Red Rider]

The way I figured it, there were 6 drawbacks to transplanting a CR250R engine into the ATC's chassis:
1. When you can find them, CR engines tend to be a little bit pricey.
2. Kickstarts backwards. Didn't want to kick through a tunnel or have to remove rear fenders to start.
3. Non-counterbalanced. After having a smooth engine, I couldn't handle that Tecate buzz.
4. No lighting coil. I sometimes get the urge to ride at night, and I like to see where I'm going.
5. CR250's are only 5 speeds.
6. Possible future transmission problems. The CR's trans might not handle the extra drag/traction of the second rear wheel.

[CartmanKXT250]

or...you can buy a CR250 and convert it to a 3 wheeler....vibration isnt bad at all, Brad Tyson of Tyson Racing or Metal Tech out in California will make a swingarm to pickup the xtra wheel...bolt on ATC250R triple clamps, forks, front wheel and rear axle assembly and your all set

[Dirtcrasher]

Agreed - not sure what the deal was with 80'S motors but my 1994CR250 had zero vibration and for that matter was the quietest most unbelievable power plant I have ever ridden.

I also like 5 gears versus 6 as there's longer ranges and less shifting to deal with.

[Tri-Z Pilot]

Motorcycles dont need counter balancers because of the way the vibration travels through the frame, put it in a trike, and the vibration gets worse, even far worse in a quad. ESR makes some good bolt on parts like bolt on powervalved cylinders, and a cr ignition bolt on kit, (cant run headlights though), I hear they have pretty good pipes and carb kits too!

[Dirtcrasher]

Motorcycles dont need counter balancers because of the way the vibration travels through the frame, put it in a trike, and the vibration gets worse, even far worse in a quad. ESR makes some good bolt on parts like bolt on powervalved cylinders, and a cr ignition bolt on kit, (cant run headlights though), I hear they have pretty good pipes and carb kits too!


No offense - but that sure sounds odd - what the heck does the number of tires have to do with anything?? Maybe I'm missing something? Motor vibration transferred to a frame to me is any frame - not just one with either A arms or a long rear axle???

[HemiChallenger71]

There's a reason why that bike has 5 speeds and less shifting, because it's made to run on a MX track only. The ATC 250R has 6 speeds for a reason, drag racing and top end speed. And the powerband on a stock ATC 250R is not that light switch, it's a bit harsh but not lightswitch, a 1970's anything 2 stroke is lightswitch. Go ride one of those and then complain. And as far as vibration, if your riding a high performance machine and even noticing normal engine vibrations maybe u should get a nice smooth riding 4X4 to put-put around on.

As far as the transmissions in the CR250R I would bet a ot of moeny it's a lot stronger. First the engine makes more power, and to get around the track, those riders pull the clutch in around a turn, and then rev it as far as it will go and dump the clutch to get out of that turn. And all the power is sent to one very skinny wheel that digs right into the dirt. Now tell me what's harder on a transmission? I've actually herd of ATC 250R transmissions being weak to an extent, and that they break if you put on meaty mudding tires or anything else like that.

[Dirtcrasher]

There's a reason why that bike has 5 speeds and less shifting, because it's made to run on a MX track only. The ATC 250R has 6 speeds for a reason, drag racing and top end speed. And the powerband on a stock ATC 250R is not that light switch, it's a bit harsh but not lightswitch, a 1970's anything 2 stroke is lightswitch. Go ride one of those and then complain. And as far as vibration, if your riding a high performance machine and even noticing normal engine vibrations maybe u should get a nice smooth riding 4X4 to put-put around on.

As far as the transmissions in the CR250R I would bet a ot of moeny it's a lot stronger. First the engine makes more power, and to get around the track, those riders pull the clutch in around a turn, and then rev it as far as it will go and dump the clutch to get out of that turn. And all the power is sent to one very skinny wheel that digs right into the dirt. Now tell me what's harder on a transmission? I've actually herd of ATC 250R transmissions being weak to an extent, and that they break if you put on meaty mudding tires or anything else like that.


Well, I must admit my comparison is to that of a 94CR250. I have heard from numerous people that the ATC 250R is all or nothing aka a ("lightswitch") and unless something is wrong with my 250R - this is what it has shown me thus far. Either hair raising top end or little low end. There is very little low end torque to drive it upon the face of a jump - it suddenly "jets" off the top somewhere past midrange and just about all top end. On my MX track with short stretches and tight turns it needs more low end like that of the 94CR250 I had which I believe would be a better motor in the ATC.

[ChrisD]

First off, sorry to vent, but I don't know what you guys are complaining about.

The new CR motors are superior. Of course. They're pushing out 58 hp stock. Welcome to technology and years of R&D. I, personally, bought a 4 stroke YZ because it has a very smooth constant powerband and wild low end power. Oh, and the 58 hp motor too. However, I don't put down the ATC motors because of their power delivery. If you want smoother power delivery, better low end and lower "lightswitch" power, then buy a flywheel weight. That will solve the problem.

If you want to engineer the motor into the ATC, then great. Most people go for the CR500 motor, but that's up to you. It's the same amount of work. Someone posted the best option already. Keep the CR and hack up your threewheeler. Take the front end and put it on the CR. It will bolt right on. and have your swingarm cut up to fit the CR. You will have a wild bike, but you have to work for it.

If you like your threewheeler (LIKE I DO), but want the CR top end on your wheeler, FTZ makes a conversion kit to put the new generation CR motor top end on the ATC bottom end.

As far as strength of the transmission goes,....whatever.....both bottom ends are great. They are a dog gear, crash box design, like a boat lower unit. They can withstand direct shifting without a clutch if necessary. The only thing the clutch does is prevent you from stalling it when you put it in gear. I've crashed my bike in the woods before and rode it out without a clutch before and the only difficult part was getting started.

One thing though....there is a difference between a 5 inch tire ripping into the dirt and two 10-12 inch wide tires digging into the dirt. Try pushing a dirtbike and an ATC. The ATC has way more drag and more weight. I don't know if the two are an accurate comparison if you are considering the "strength" of the transmissions. I race on the ice and in the woods and I have NEVER broken a gear. I have to admit that I don't know how a CR transmission would hold up either if you hooked up a set of 25", six ply tires that weigh 40 pounds each, so I don't think that arguement holds water with me.

Just my opinions of course. Sorry if I offended anyone.

[Tri-Z Pilot]

Dirtcrasher, it's true. I read about it some where, and a quad is the worse because of something to do with the a-arm suspension. On trikes it's not as bad, because of some way the vibration travels down the front forks to one tire it has less vibration than a quad. It happens a lot less on dirtbikes, because you have the the front forks and one tire (as stated above), and there is something about not having an axle and two tires that cuts down the vibration on a dirtbike, I'll try to find the article, I think it was in one of my dirtwheels.

[HemiChallenger71]

Hey good opinions, anyone ridden the new TRX250R from service Hodna yet? I'd like to see one of those...

[Tri-Z Pilot]

You mean the 400ex chassis with the cr 250 mill stuffed in it? I would love to have one of those.

[Dirtcrasher]

If you want smoother power delivery, better low end and lower "lightswitch" power, then buy a flywheel weight. That will solve the problem.

Hey, now thats a great suggestion! I've asked that question before and had little response.

Is there a heavier flywheel and maybe a pipe and jetting combonation that will give me some more low end?? I would love to hear any suggestions.

[Red Rider]

Rather than converting a 2 wheeled motocrosser into a 3 wheeler, I'd rather just transplant the dirtbike's engine into the the 3 wheeler's frame & deal with the resulting problems/drawbacks that I mentioned earlier. At least that way you'd have a frame that was designed to handle the stresses that a 3 wheeler imposes on it, plus it would have the proper frame geometry, so it would still handle properly.