CR85 in 250R

[marsrace2]

anyone here done a 250R wih a CR85 Motor? I am getting ready to put one together for my son and just looking for ideas and tips from someone who has done it before. Biggest question at this point is what to do for exhaust?

[ZSNOW]

250Rbadboy did a 85 hybrid. PM him.

[deathman53]

Jason Hall did one with a atc frame.

[marsrace2]

we are doing an 87 TRX 250R chassis. Any pics from anyone that has done one would be appreciated.

[250rbadboy]

heres some pic for you. this is for sale.I also have a extra head pipe read to go ill sell you.<a href="http://s91.photobucket.com/albums/k292/stevensred8/?action=view&current=dadspics002.jpg" target="_blank"><img src="http://i91.photobucket.com/albums/k292/stevensred8/dadspics002.jpg" border="0" alt="Photobucket"></a> <a href="http://s91.photobucket.com/albums/k292/stevensred8/?action=view&current=dadspics001.jpg" target="_blank"><img src="http://i91.photobucket.com/albums/k292/stevensred8/dadspics001.jpg" border="0" alt="Photobucket"></a>

[ZSNOW]

that frame that 250rbadboy has is sweet. i saw it at english town

250rbadboy did a A+ Job on that bike..

[Jason Hall]

How do you plan on running the chain over the swingarm? Are you going to move the swingarm pivot bolt location up some?

[marsrace2]

250R Bad Boy, I cant use your engine since I think your post said it was a 101, I need to be at 90 or less. I could however use your mounts and pipe if you were selling seperate.

[marsrace2]

havent gotten far enough yet to know anything about the swing arm, not sure what I will run into yet, that is why I am asking questions before I start.

[250rbadboy]

i like to sell the motor and frame together.I have a stock cr85 ill put together for it. ill let it go for $750 and shipping.the extra head pipe was off the first 1 we built.$60 and shipping. if your interested pm me. or just ask what you need to know to build your mod. ill help out with any thing you need to know.

[AJMorrison]

From what i understand lengthening the pipe can really effect the power of the motor. I guess its all about sound waves. I have built a couple mods out of blaster frames and i allways cut and bend the pipe. Some of the guys that we race with put extensions on the pipe to get around the frame and the things never really ran right. Of course I am no expert just tryin to help.

[mini]

on ares i just cut and twisted the pipe did not add or shortin the pipe ,adding to the head pipe will change the tuning, son now has a cr125 and i did the same .

[marsrace2]

could one of you that has done it post some close ups of the motor and mounts?

[marsrace2]

well the 250R Rolling chassis and a complete CR80 Dirtbike will both be in my garage by the end of the week, so time to get this started any help is appreciated.

[Jason Hall]

I put a CR85 engine in a 86 ATC250r frame. You need to make sure the chain Is straight before you mount the engine. Here's a few tips from my build. The CR85 has a 420 chain, the 250R has a 520 chain. A stock CR85 rear sprocket has the same size bolt circle as the R. You need to figure out what size CR85 sprocket you want. Then drill the 85 sprocket hole's out to the 250R bolt size (10MM), then machine the CR sprocket to fit the bigger counter sink of the 10mm bolts. Once you have a 420 rear sprocket mounted, you can start to line the engine up. The left side of the swinger will need to be narrowed to keep the chain straight. I also made a very thin bushing for the swingarm bolt hole In the rear of the CR engine. The trx swinger bolt is slightly smaller than the 85 bolt. Will you use a steel swingarm? or a 88-89 aluminum one? If you use the aluminum swingarm, you will need to cut the center of the pivot bolt end out, so the swinger bolt can be put through the engine. I used a cracked 89 arm on mine, to keep the weight down, and to snuggle the rear tire's up under the bike so It would fly flatter when jumped.

Hope this helps some, If you have other questions as you go, I'll help you any way I can. Here's a couple pics of my little guy on his 3 wheeler.

IMG]http://i237.photobucket.com/albums/ff42/Jasons450r/ATC2085-R.jpg[/IMG]


http://i237.photobucket.com/albums/ff42/Jasons450r/jabobupnorthba.jpg



http://i237.photobucket.com/albums/ff42/Jasons450r/atc85ratTF062.jpg

[blazen582]

Depending on the size I the rider I would do a TRX 90 frame.. Fits perect..