Atc250r 4 stroke swap

[fordnut79@hotma]

Wondering if anyone has ever put a 4 stroke motor into their atc250r. I was thinking it would make for a nice plush, mild mannered woods bike. Kind of like the ultimate 200x or something. Don't hate on me, just wondering, lol.

[Jmoozy27]

It just kind of seems pointless with the 200x motor. Now a 300ex or 400ex would be the ticket. Maybe even the xr600.. That would be a bucking bronco. Not sure what the stock 250r frame is capable of.

[jb2wheels]

... was thinking it would make for a nice plush, mild mannered woods bike. Kind of like the ultimate 200x or something ...

Sounds like you want a 350X to me.

Or a project.

[oscarmayer]

^ exactly!! 350x fits that bill


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[Jmoozy27]

That would fit although some machine like the 350x are pretty hard to find in decent shape. And when you do, they are always priced to damn high. I have seen a few 300 or 400 quads In my area selling for about $1500 running. I can get a 250r frame for pretty cheap. $100-$150 bucks let's say. And keep in mind he may want something no one else has. I am definitely guilty of wanting a 1 of a kind machine. But you have to be ready to sacrifice time and money.

[fordnut79@hotma]

Like a mild mannered 250r that could crawl like a big red but still soak up the bumps good when it had too. Yes, like a 350x, but not as heavy or hard to find,and I love the look of the R. Cant believe nobody has done it yet considering how many broken 250r motors there are

[bkvette3]

Sorry - but that is just wrong. Save the hassle and just find a decent 350X and get out there and enjoy.

[RIDE-RED 250r]

I would say the lions share of weight difference between the 350x and 250r is the difference in weight of the engines. Put a thumper of larger displacement (350cc and up) in an R, and I bet you are right up there in weight, comparable to the 350x.

350x claimed dry weight is what, 315lbs?? Not a big difference really.

There is a member here from across the pond that shoe-horned a 450r engine into a 250r. It is an EXTREMELY nice build with the utmost attention to every detail to make it right. It was a very involved conversion. I do not recall the member's name...

From what I can see just looking quick without measuring, you would have some issues to overcome due the taller thumper engine compared to the shorter R engine.

IMHO, the X's, even the 200x (particularly the 2nd gen) fit the bill of what you are looking to do quite nicely. Rather than go to all of the work and expense of making another size/type of engine work in an R, I would spend the money on a nice X.

[Red Rider]

There is a member here from across the pond that shoe-horned a 450r engine into a 250r. It is an EXTREMELY nice build with the utmost attention to every detail to make it right. It was a very involved conversion. I do not recall the member's name...http://www.3wheelerworld.com/showthread.php/74595-Honda-HRC-450RR

[Jmoozy27]

Or a Super X :D

[onformula1]

Or a Super X :D

Are you thinking about what I am thinking??? :lol:

Rhymes with 6-5-0 :lol:

[Mr. Clean]

The perfect conversion has been done, well at least in my mind. Thanks to Ol Deuce!!!! With a little help from his friends. Of course not with a 250r frame, but yeah its SWEET. I could do way more with this than a 250sx :cool:

http://www.3wheelerworld.com/showthread.php/168757-86-200x-Conversion-E-START-REVERSE-AUTO-CLUTCH

[Racer-X]

I think a 250r as a 4 stroke would be like a crotch rocket as a V-twin or a corvette with a diesel motor.... its like........ "but why"? Especially with all the modifications that would have to be done. Its not worth it to me. I agree with everyone saying that you probably want a 350x. If you did have an R, I would leave the 250r as is and change the sprockets for more torque if you want it to be better in the woods. Add a few teeth to the rear sprocket or drop 2 teeth on the front sprocket. You won't be crying about torque or no low end power anymore. You'll be looking for lead to keep the front wheel down Lol.

[atc300r]

It would take a lot to put a big 650 4 stroke or even a 350x in a 85-86 250r frame.The 85-86 atc 250r has a small engine cradle. I started this project last fall. My plan is to put a 200x motor in the liquid r frame to see how it does at MX. Nothing wrong with a 200x frame but they do lack a lot in suspension for MX. I was going to wait to start a build thread till I was further along with it. But I saw this thread and figured why not post some teaser pics. Do worry this frame was headed for the scrap pile .The motor is for mock up. Im going to buy a 200x motor later on. I don't want to use my 84 200x motor yet.215733 215734 215735

[Jmoozy27]

Are you thinking about what I am thinking??? :lol:

Rhymes with 6-5-0 :lol:

I was looking at the xr frame. it doesn't look like it would take much. That may stay on 2 wheels until I get tired of it though

[RIDE-RED 250r]

I think a 250r as a 4 stroke would be like a crotch rocket as a V-twin or a corvette with a diesel motor.... its like........ "but why"? Especially with all the modifications that would have to be done. Its not worth it to me. I agree with everyone saying that you probably want a 350x. If you did have an R, I would leave the 250r as is and change the sprockets for more torque if you want it to be better in the woods. Add a few teeth to the rear sprocket or drop 2 teeth on the front sprocket. You won't be crying about torque or no low end power anymore. You'll be looking for lead to keep the front wheel down Lol.

Or increase displacement significantly... :naughty:

[YamaBoss]

I think you guys are missing his idea here. He wants nice mild motor machine. Something like a big red with the suspension of a 250r. The last thing he wants is a 350, 400, or 600 motor.

[fordnut79@hotma]

Exactly Yamaboss.

[atc007]

Everyone is different.. You can see the west coast guys,liking a 200x or 650. Where us woods guys want almost exactly the opposite. It all depends on where you ride,what you ride. We're ALL different. Hence, Kawasaki actually sold Tecates, Yamaha actually sold Tri 'Z's. After the 250R had been dominating off road racing for years. We're all different. If you want a 4 poke R, I say make it happen!

[Jmoozy27]

I still say it sounds like a super x. Performance meets comfort and simplicity. Not a very hard build once you find the motor. A lot of options once you do.

[Bilster]

I've floated around the exact same idea. My 250R was a handful in tight, soft tracks. My 200X was so much smoother. I didn't work nearly as hard to go fast. I have a 86 200X frame and when I inquire on how to make it the ultimate handler, it basically ends up being a 250R chassis. Why not just start there? Keep us posted. I will eventually try it myself but I'm up to my elbows with my 86 200X motor into a 1991 CR125 chassis.

[RubberSalt]

I'd look into increasing compression, add a reed spacer, and clean the ports up. Don't raise them, just clean them up. In same cases, epoxy them. in.

Your port size is going to be relative to your target RPM range, displacement, and compression. More compression requires bigger ports. By raising compression, you are technically lowering the rpm that achieves peak hp... By raising compression, you are adding power all around.

Now if you have no motor and are looking for a 4 stroke, then there are tons of options. I'd recommend a CB350 engine. Light weight, reliable, and plenty of power. And yes, I'm talking about the old stuff. http://en.wikipedia.org/wiki/Honda_CB350