CR250 YSR

[YSR89]

Hey, I have a 2000 CR250 motor, and was thinking of doing a motor swap sometime in the future. I have seen it done twice, once with a YSR frame, and once with a pretty trick chromoly frame, but I havent seen any detail pics. I just got done with my DT175 swap, So sometime over the summer I'll need a roller, if anyone has one sitting around. I'd rather get a full YSR, with a seized/no motor. Has anyone else seen a YSR 250 , or have pics?

[cdiaz3]

If you really want to put a 250 2 stroke in ysr...

Make sure you get one that is BALANCED. You can get a Kawasaki Tecate4 250, a Suzuki LT250r, or a Honda TRX250r. All these motors have a counter balancer, a 12v lighting coil, and they all have enough power to kill you on a ysr if you are not careful. You might also want to call Team Calamari and get yourself an aluminum swing arm with a 3 inch stretch with the better wheel adjusters on it. I have a blaster in a YSR and I already broke one of the wheel adjusters off and my wheel moved towards the right and my chain came off. Luckily I was only in first gear. Also, good luck getting someone to make you a pipe that works. And don't forget to brace and box the frame.

[Manimal]

CR250.......

with that kind of motor, the YSR chassis needs to be boxed in and braced, well. That's a beast of a motor and can only imagine the vibration it will produce. If it's any thing like an 80cc motor, your limbs and butt will go numb within 500 feet of your ride :cry :cry

[cdiaz3]

CR250.......

with that kind of motor, the YSR chassis needs to be boxed in and braced, well. That's a beast of a motor and can only imagine the vibration it will produce. If it's any thing like an 80cc motor, your limbs and butt will go numb within 500 feet of your ride :cry :cry

Manimal is right. That's why you have to make sure that the motor at least has a counter balancer. CR, YZ, KX, etc... dont have balancers in them which is why you get the vibes. I am not saying that you wont get vibes with a balanced motor, but it will be a lot less.

OR... You can go with a 250 four stroke and you wont have to fab an expansion chamber. You wont have to mix fuel and oil. And you can go longer periods of time without a rebuild. And it will be more streetable. You can grab a YZ250F, WR250F, CRF230, TT-R230, or XR200 or any motor that you think might fit in there with a little welding. Just stay away from the Ninja 250 idea, that motor only makes like 3 HP more than a YZ250F and it will be hell to wedge it into the YSR frame cuz it has two cylinders, plus then you would have to be synchronizing carbs and shit.

[YSR89]

Hey, Carlos! I got the DT175 running real nice. I still don't trust fedex. :laughing You should send me some pics of the blaster, I have the midway done photos, but non of the finished bike. The reason I'm doing the CR250 is because I already have the donor bike. I've got the DT YSR, so I already have a relatively good street motor. Rough rides and vibration has never really bothered me. This is strictly bike I'm building for the "Holy shit, what a ride!" Factor

[cdiaz3]

Wuz up Matt,
I haven't taken any pics of the conversion, but when I am done I plan to do a post listing EVERY single little detail that I can remember so that any fellow barfers can duplicate it easily without having to take wild guesses. Things like...

Exact wiring instructions including the use of a battery
What gearing and where to get the sprockets
what throttle and clutch cable
What PIPE to use since Tommy Crawford isnt fabbing up pipes anymore
etc, etc...

I am already riding her around the block trying to get the jetting dialed in. She runs great at wide open throttle and at 0 to 1/4 throttle, just trying to get her to run smoother in the mid throttle area (jet needle adjustment). Once the carb tuning is done all I have to do is put the fairings back on and she's ready to go.


About doing the CR250... Can you weld? If you can, weld the hell out of that frame, make it as sturdy as you can. And pay close attention to engine mounts, chances are that with the combination of power and vibes you will be breaking them often. And don't forget an extended, braced swingarm with stronger chain adjusters.

[YSR89]

Cool! A guide would be awesome for those who are looking into doing the Blaster swap Carlos. From my DT Experience, photos of mounts and the such are very helpful. If you've seen that Japanese site about the TZR125 YSR swap, that guide is set up very well. As for the CR, I can weld somewhat, but I talked to my cousin about the project. He's a Union sheetmetal worker, and can weld pretty well. I've already planned to brace the hell out of the frame, and make duplicate mounts (for when they implode from the vibration :laughing ) Even if it doesn't entirely work out, It'll be an interesting project at the least! I won't actually be able to start the project until sometime in the summer, but I'm trying to gather all the info I can. (And there's 4 ft of snow on the ground, and my garage is around 18 degrees :| )


If any of you guys come across a cheap roller, let me know. I'm trying to et it as cheap as possible, because it's an "experimental" YSR from Hell :teeth



It's kind of funny, I just finished the DT Swap before the winter, and now I want a 250. Come to think of it, if a CR250 will fit, a CR500 will fit too, right :laughing

[cdiaz3]

Come to think of it, if a CR250 will fit, a CR500 will fit too, right :laughing

Screw it, lets stuff a small block chevy in a ysr and head out to the salt flats!!:loco

Ok, back to sanity...
I've seen a crap load of rollers on ebay lately. From just frames to complete bikes minus motor.


Here's one right now, Item number: 330211193428. Complete roller.

[YSR89]

Hey, It seems I have reached an impass with the pipe for this bike. I have an FMF Gnarly pipe from the CR,but it's not going to work. Do any of you know if the older 250 pipes will work? Would a pipe from a '73-'73 CR250 fit the exhaust port? I've seen a YSR/CR80 where they used the stock pipe, the up and around the cylinder design you see on bikes like an '85 CR250.

[cdiaz3]

Believe it or not, the pipe will be one of your biggest hurdles in a two stroke swap. The pipe controls a LOT of the aspects of a two stroke, how hot the motor runs, peak torque and hp and where in the RPM band they are made (powerband). If you put the wrong pipe on there it will run like shit no matter what you do with the rest of the setup.

If you can't find someone to fab you a pipe then your other alternative is to cut the stock pipe in half and measure the different INNER diameters, tapers, and lengths of the cones and try to make one yourself. Which will take some welding skill, time, and luck.

OR you can find a motor that has similar (close as possible) parameters. Things like bore, stroke, exhaust port diameter and length, port timing, etc...

At the end of the day, I don't think it's worth going through all that trouble. I would just stuff a four stroke in there and not have to make or find a pipe.

[YSR89]

Yeah, I talked to Lee at On the pipe racing, he knows where I can get a 73-74 CR pipe. I'm not really interested in getting the most I can out of it, just a fun project since I have the parts laying around. I might end up selling it if all goes to plan and it works. Just gonna have fun with it:thumbup

[PainterDude]

If you need detailed pics of a YZ250F four stroke in a YSR I can help you out.... Bike is very fast, & very rideable unlike a 2 stroke....If you want more get a 450, block is same, just longer stroke so motor is a bit taller, but everything else is same, so I have done all R&D....

I personally want a street legal NSR so I can put a CR250f motor in it & have a Rossi - Hayden dual on mini's....

[YSR89]

Hey Painterdude, Your YSR is the Rossi Replica right? That's my favorite YSR I've seen so far! Yeah, pics would be awesome. I was actually planning on doing a 4 stroke YSR for my next Swap, right when I got done with my DT175 YSR. The only reason I wanted a CR250 engine is I have an extra one right now. Then again, I could probably sell the motor to fund a 250F...

[cdiaz3]

Matt, how fast have you been able to go with the dt175? If it's anything like the blaster motor I would say it's more than fast enough for a YSR chassis. you should be able to accelerate like a raped ape and you should have a top speed of about 80 to 85 mph.

What's you gear ratio? How many teeth in the front and rear sprockets?

[YSR89]

Hey Carlos, I don't really know how fast I can get on it. I only had it done for a short time before winter (Started in November, still going strong now with about 5 feet of snow on the ground) I never got it to any good sized open spaces. Compared to the Blaster, the DT has a slightly higher top speed, but can't match the acceleration, but it all really depends on the gearing. As for the gear ratio, Whatever the front was when I got it (I'll check sometime) And the rear is 37 tooth. It's geared a little short, but it accelerates unbelievably quick. If your not leaning forward on the bike when you get on the gas, the more you roll on the throttle, the higher the front wheel comes up :thumbup I'm very happy with it, but I'd love a little 4 stroke YSR for cruising around. I always take performance over comfort, just my syle. That's why I am entertaining the idea of a CR250 YSR.

[YSR89]

Hey painterdude, do you have pics?

[PainterDude]

Sorry,

Been too busy for internet lately...I will getsome together for you....

[YSR89]

Thanks painterdude! Don't worry about posting them quick, no rush. That's still gotta be the sickest YSR Ive ever seen.