1985 ATC 500 Build

[dzolalaw]

I am looking for information on building a CR 500 powered atc 250r. I am looking for information regarding exhaust choices, sprocket sizes/gearing.

I have almost everything I need, in process of putting it all together.

Any help would be greatly appreciated.

[plevib]

ok no one has bitten yet so i'll chime in. Why? for the price of a cr500 motor you can make a 85r really powerful.
Not trying to be insulting, I like a good project too. I just think for you money and time you'd put in you could get just as much performance out of the 250r motor.

I recently sold my 250r that i put a 310 kit in it, gave it tons of power. The ESR kit was on sale for 500 bucks. I was very happy with the motor.

https://www.youtube.com/watch?v=d56PXFOmx48

Just some thoughts. Best of luck!

[atc300r]

I traded my 230 quadsport and a few bucks for my motor.I hadent done anything with the quad in 20 years.It just sat in my garage.

[Baba Yaga]

There's no replacement, for displacement!

[Red Rider]

There's no replacement, for displacement!Unless you misplace your replacement, that had more displacement, then what are you supposed to do?

[Baba Yaga]

Don't be complacent!

[Red Rider]

Spoken by a man who knows. Good idea, I'll start searching the basement, or somewhere adjacent.

[Billy Golightly]

I am looking for information on building a CR 500 powered atc 250r. I am looking for information regarding exhaust choices, sprocket sizes/gearing.

I have almost everything I need, in process of putting it all together.

Any help would be greatly appreciated.


There has been a bundle of builds here over the years if you spend some time searching you will probably find several to work off of.

For a pipe it depends on if you want to keep an inframe pipe or if you're going out frame you can get shearer or ftz or whoever to build one you.

Going in frame is tough. The volume required for a pipe makes snaking it around in frame pretty hairy. The FMF pipes for the 89+ CR500s are the easiest to modify. You can cut them in 3 places and just turn the pipes and get something that will fit decntly on the frame and around the gas tank. That is the absolute shittiest pipe to use on a CR500 though unless you want nothing but a 4 stroke like grunt bike. In which case it's perfect.

The 89+ Procircuit Platinum pipe is a more higher RPM better pipe in my opinion but it has some unique challenges to making fit.

That's about the only 2 I ever had any relative amount of luck adapting off the shelf CR500 pipes to use in conversion. you might get some like LED to make you a custom from scratch one but you're gonna shell out a grand by the time it's over and everyone seems to hang and position their motors in the frames a little differently so it still may not fit just right either.

Don't try and use and adapt a pipe off another bike. And make sure your stinger tubing leaving the expansion chamber to the muffler is at least 1.1250 in diameter. I used 1.125 stinger tube on one of my builds and cooked the top end. was witholding too much exhaust gas.

[Billy Golightly]

Andy gearing is not significantly different. run whatever front sprocket you would have on a 250r and whatever you want on the rear. There isn't a huge or even discernible difference from the bike usage to the threewheeler. I think I was using like 15/40 on mine mostly just to make it where you could lug and use the torque more. Gear lower if you're going to drag race...