RM250 powered 400ex Build

[711streetfighter]

Version 3 of the pipe much much better.. Got it straight this time took forever with the little time I have had for it. Anyways it splits in the middle so you can fit on to the quad and remove it. I have it all tacked together and still have to add the mounts for the pipe and the springs to hold it together. I know it's ugly right now but I'll sand blast it and grind it all smooth then give it a nice fresh coat of paint.

[beaverclever02]

That thing is def gonna throw peopple for a loop when they hear and see it roll up.. Not to get off topic but how do you go about checking chain alignment? To you square off a line beside the quad and go off that? It seems lke squaring the motor in the frame would be a pain, I mean and 1/8th" could be a problem, right?

[711streetfighter]

Here's how I did it, yes in the quad would really suck. I removed the swingarm from the quad and left the bearing carrier, axle, rear sprocket, and wheels on it. Then I took a piece 4 ft piece of angled aluminum stock I had and clamped it to the outside of the rear sprocket. You have to use and angled piece to ensure it is straight. I suppose a level would work also but that's what I had laying around. Then I slid the swingarm pivot bolt in with the motor between the swingarm. Then I simply used a depth gauge to measure how far left or right I needed to adjust after measuring to the outside of the countershaft sprocket. Then I simply cut out what I needed out of the swingarm and made bushings to take up the slack on the other side. To make the bushing I used the 400ex long swingarm bearing insert from the right side and cut it down with a 1/16th inch washer. You have to be less then 1/16" off as I understand so that's what I aimed for. I was really really close to perfect but some guys get it close and then shim out the rear sprocket.
After the alignment was set then I put it back into the frame with the motor and used a jack to get the engine height where I wanted and fabbed up the front motor mounts. Once those were bolted in I did the top mount then set it up on the grab bar and did the bottom.

[timgoob]

looks like your doing great job. thats going to be bas a$$. cant wait for the final ride review. good luck the rest of the way.

[decentZ89]

thats awesome but please paint the blue frame lol

[CFM-Z440]

This is a really cool project. Might have even inspired me to find a rolling chasis for my yz 250 engine

[711streetfighter]

Originally Posted by decentZ89

thats awesome but please paint the blue frame lol

It'll stay blue for a while. I'm not gonna dump money in it until I've got the bugs worked out and it performs the way I hope it will.

CFM you should do it, you won't believe how light these things are. Cruise craigslist and you'll find something. Think about it you'll be loosing around 75lbs off it. The z might be a easier swap with less fab since it already has a radiator and a 17mm swingarm pivot bolt (I think it is anyways) where the ex has a 15mm depending on what size the yz's is. I really wanted to do a kx500 swap but they're hard to come by and cr500's are just way to expensive. Anyways what year is your yz? you might be able to swap in a old wr250 transmission to make it wide ratio.

[711streetfighter]

Finished the pipe and silencer mounts as well as extended the kickstart to clear the frame. I cut the kickstart shaft right before it goes into the cases and welded a stanley 14mm 3/8dr socket back in between them. I used the socket because it was almost the same diameter as the shaft just .20mm smaller so I could fit the clutch cover over it.



Shaft with the socket welded in and filed down. It added about 1" length.


a video of the extension installed.

[suzuki-al]

badass build! very nice!

[711streetfighter]

Here it is, fired up for the first time. I still have to take it all apart and paint the frame and do the little nik-nack stuff but it's a runner.

You Tube

You Tube

[sd1]

nice job....that pipe will keep your leg warm in the winter he he ...

[stunmai]

Originally Posted by 711streetfighter

Here it is, fired up for the first time. I still have to take it all apart and paint the frame and do the little nik-nack stuff but it's a runner.

You gonna throw a pillow on the frame and take it out for a down and dirty test ride first right?

[711streetfighter]

Originally Posted by sd1

nice job....that pipe will keep your leg warm in the winter he he ...

Actually that pipe isn't that close. The pics are deceiving, it's low about shin high and pretty far forward.

Originally Posted by stunmai

You gonna throw a pillow on the frame and take it out for a down and dirty test ride first right?

Na Ill throw the seat on and take it out tomorrow maybe.

[CFM-Z440]

Originally Posted by 711streetfighter

It'll stay blue for a while. I'm not gonna dump money in it until I've got the bugs worked out and it performs the way I hope it will.

CFM you should do it, you won't believe how light these things are. Cruise craigslist and you'll find something. Think about it you'll be loosing around 75lbs off it. The z might be a easier swap with less fab since it already has a radiator and a 17mm swingarm pivot bolt (I think it is anyways) where the ex has a 15mm depending on what size the yz's is. I really wanted to do a kx500 swap but they're hard to come by and cr500's are just way to expensive. Anyways what year is your yz? you might be able to swap in a old wr250 transmission to make it wide ratio.

My YZ250 is a 92. The bike is getting a little clapped out, but the engine is still really strong. Even as old as it is, it's completely competitive with the 450 crowd. I have a Procircut pipe for it also that I could chop up and make work. It is for the wrong year bike, but it's pretty much the same engine.

RRGUY had a Gas Gas that was a KX500 hybrid. That thing was a BEAST!

I'm liking this idea, because my Z is getting a little ridiculous for motocross. I'm starting to see the need for more use specific quads. The Z can become my duner and dragster, and freak of nature guinnea pig, and I can still have the YZ hybrid for mx. It would be great to have such a light mx quad.

Not only that, but my girlfriend likes to ride, and she likes my Z which means I end up on the YZ more than I care for. I'd way rather ride around on a hybrid. I think a hybrid EX would be sweet! That's a good chassis, and so much stuff is interchangeable between it and the Z.

[711streetfighter]

That yz should make a sweet donor. The main reason I'm doing this is because I just like to be different. If it works great more fun for me, if not well at least I learned a ton of new things doing it.

I'll say the pipe is the hardest part by far, you're an intelligent guy so I'm sure you're capable. Probably much more then I was when I started. Anyways when I started I kept cutting it and tacking it back together trying to make it work but it was never right. So I completely cut the first foot out (where it snakes back and forth after the exhaust port) and made my own trying to stay as close to the diameter/length of the rm pipe as possible just in a straight line. Then I just cut away at the rest where I needed to and tacking it back together. Took me a month spending every friday night from about 9pm to 4am then whatever spare time I had the rest of the weekend messing with it to get it right. Everything else was pretty straight forward except for some minor mistakes on my part. One example, I made the top engine mount/cross member to close to the fuel petcock so I had to cut off the on off petcock and thread in a straight 1/4" nipple for the tank to sit right.

The engine mounts were pretty straight forward just 3/4" tube with 1/8" flat stock. The bottom radiator mounts were just 1/8" flat stock welded onto the downtube. The upper ones I used 1/2" round stock drilled and threaded for m6x1.0 bolts welded to the upper frame rail. Then used some more 1/8" flat stock to bolt onto those then to the top of the radiator (which is rubber mounted). Everything on it is solid mounted except for the radiator. I think alot of guys have problems with cracked frames because they don't realize that the engine is a stressed member of the frame. The frame needs the engine there to resist bending and twisting. So when they go rubber mounting everything which really adds a lot of stress to the frame. That's just my opinion on it.

BTW my fabrication/welding skills were pretty basic before beginning this project. You might or probably have more experience then me. I had o/a welded in high school 20 years ago and used a mig welder a few times before this. I understood the theory and basics of it but had little hands on knowledge. Now I can tig, mig, and stick weld. Sure they're not as good looking welds as a professional but they're solid and my confidence level is way up. I probably could of saved some time/money and got a trx250r pipe and went from there but where's the fun in that.