R engine in ex frame??

[la400ex]

Im sure this question has been asked a million times but how would that work? I searched it and didnt find very much info. I really dont want another ex motor. I cant afford a crf or yzf. Is it worth doing? Im sure the best thing to do is to buy an R frame. I dont have the money to do that. Thanks, Ant.

it's been done. i think it would be a easier conversion than the crf yzf swap. i wanna do it to if i don't do a service honda cr250. the ex chasis rides better and the r motors faster.

[la400ex]

Yea, that service honda bike sounds bad but how bad is it gonna vibrate? I was thinking that putting the R motor would be easier than a yz or crf. I just love 2 strokes and the modern 4 strokes. I will probably just end up putting another ex engine in it but man i dont want to. Im thinking about stripping it down to the frame and letting pappy powdercoat it. Then just building it up slowly. Im gonna be getting a check for around 1000 a semester from my scholarship. I figure that could go on the project after i buy books and the college that im goin to has books to rent instead of buy. It would be my luck that just after i get done with it, honda would come out with a new 450. Oh well. Later, Ant.

yeah but a r motor in a ex frame is just cool

[ieatglue]

the R engine in the ex frame would be a really easy swap as long as the pipe will fit in the frame. if you would make a rear motor mount and bottom motor mount on the frame then i think you could get a 88 style R swing arm to fit or put a spacer in the ex swingarm where the back of the engine sets. i think the ex rear shock and linkage would even work with the R swingarm. you would also have to make mounts for a radiator. there are probably be a few more small things but it would be pretty easy. it would be like putting a 350X motor in a R frame but backwards. i would try to get a R motor and stay away from the dirtbike motors since they don't have a counterbalancer.

what about the atv rear motor mount. i know if floated on the swing-arms bolt. it might have on the 86-87 r also. then you could keep with the ex swinger

[ieatglue]

the 86 and 87 did but i don't know how wide it was. chances are they are not the same width. if they are though then that would be to go. the 86-87 rear floating motor mount is 3 15/16 inches wide. just shy of 4 inches. if the gap in your ex swingarm is close to that you may be able to run it.

[la400ex]

So I would have to make mounts for the motor and radiator. How hard would doing this be? My neighbor is putting a chevy V8 in a lawn mower so im sure i could get some help. I know thats hard to believe but they do lawn mower pulls. They have some pretty crazy lawn mowers around here. I also have an uncle with a honda goldwing engine one. Hes a welder so he could probably help me make the mounts. Anybody selling an R motor? If i find one, i would be selling my stock carb, R-4 slip on, oil cooler, oil tank, and maybe my swing arm if it would work with that motor. Has anybody done this? If so, can you give me some pointers? Thanks, Anthony

the gap on the rear mount for the 400ex is just shy of 3 1/4". can the 250 rear mount be trimmed down any.

[ieatglue]

the motor mount wiould not be able to be trimmed down. your best bet would be go with a 86-87 style swinger with the rear motor mount in it or go with a 88 style swinger and weld a motor mount on the frame just below the swinger.

i wonder if the atc mounts are any different

[Teufel]

i hope you realize how much fabrication work it would require. Personally I would put the 400 engine in and sell it. :confused:

actually..i'll be right back

i forgot the swing arm has a spacer in it to space the motor. the actual swing arm gap is 4 1/4"



it's got my brain thinking hard :devil

[ieatglue]

the atc rear mounts are the same. i have a 85 atc also, its like riding a live bull.:D

i may have to find a r motor.. i wonder how much i can get a r motor and everything for.

[ieatglue]

Originally posted by MX#132
i forgot the swing arm has a spacer in it to space the motor. the actual swing arm gap is 4 1/4"



it's got my brain thinking hard :devil



well then you could probably make spacers and use the stock swinger. if thats the case you would only have to weld on bottom motor mounts, make some front ones and throw a pipe on it and you will have a honda running the way its supposed to.

if that rear mount would work that would eliminate alot of fab. i wanna do i but i also have blown a few r motor so i dunno.

[la400ex]

I know its gonna take a lot of fabrication but I think it would be cool to have. I want to do it but i dont know if i am yet. It really just depends on if i find a motor. I really want to have something different. Im not in any hurry. I dont race yet so i dont have any time to get it done. I figure that I can just take my time and build the quad that I want. Who knows, i might sell it and try to find an R. I dont know yet but right now, im seriously considering putting in the R motor. Thanks, Ant.

do it. i am thinking about it now

[la400ex]

I think i am. Im gonna talk it over with my dad first. Im already thinking about what mods i want to do to the motor. Later

[la400ex]

I talked to my dad and he said its ok and he would help me out. Hes pretty good with a welding machine. I also have a friend from school thats gonna help me. Looks like im gonna have me a 250r/ex. Thanks, Ant.

[ieatglue]

good luck. don't forget to post some pics while you are working on it.

[la400ex]

Thanks, i will keep yall updated. Me and my dad have been talkin about it. Hes got some doubts but I think with some help, we can do it. Just gotta find a nice R motor. Ant.

cool. can't wait to see how it comes out. take your time and do it right the first time. good luck:)

[stocktires]

Ant,
Personally I wouldnt do it, I would just build an R.
But if you do go through with it, you can come look at my R anytime you want to check any of the mounting ect.
After you do the swap, your 250R/EX probably wont be worth a whole lot as far as re-sale value :(
I say sell the ex (after buying a cheap replacement stock motor) and build an R, ground up (thats the only way to do it right).
Goodluck on ya decision! :)