Unique machine wanted.

[greeny250sx]

NO AV GAS..never run it..unless its going to be a drag bike and nothing else..av gas is meant to be run wide open all the time..run vp red.

[matt123]

Originally Posted by 2002 cr250r

whats a nasty ole big red ?

A big red is a honda 3 wheeler. most were 200's but they went to a 250. the 200 had no rear suspension. They went good for what they where though and were a lot of fun.

[2002 cr250r]

ahh i see. thank you

[tecateboy]

Originally Posted by greeny250sx

NO AV GAS..never run it..unless its going to be a drag bike and nothing else..av gas is meant to be run wide open all the time..run vp red.

theres nothing wrong with running AV gas, quite a number of people on here run it in their machines, but it wont add any power, not unless you have higher compression that would need it to keep the motor from detonating.

[ChrisC]

Kane, I dont use it when I dont need it. But I'm wanting to make a drag racing bike. I currently use it to go over to friends house, nothing much besides that. Couple miles of gravel road, mile or so of pavement. I've got plans of turning this "daily driver" into a weekend drag toy. And for the boring the cylinder, Why bore for the smaller amounts of power, and end up needing a bore in the future, and cant?
I was hoping I could get a little help from somebody who knows enough about the 85's. As for getting a 125 or 250, Yeah, I could, But that's not too very unique, is it? I'd like to have a powerful CR85 to have a little fun on.
I'm thinking porting, head milled or whatever gets reccomended there, pipes, reeds, Possible piston type change, Air filter, And I'd like some information on stroking the smaller engines. Have I missed anything?

[Kane]

Nope, I think I got ya now. You're basically bored with what it is and want to turn it into a different animal, for a different use. Thats easy enough.

Boring it out with the normal run of oversizes is a waste of time. The marginal increase in size is a waste of time and a loss of future rebuilds, much as you already know. If you're not going to go into big-bore mode, thats not a good direction to take.

Start with the obvious..........a good aftermarket pipe system, V3 reed cage, K&N filter, CR125 intake boot and carb or a new 30mm PWK, send the cylinder out for porting (I'd reccomend Eviltwin/Flotech), get with eviltwin on possible millwork on the head to increase compression/altered squish.

The problem with finding info for stroking on anything other than a cart site is you end up making the engine size enter a new class. So, not many MX'ers will go that route as it's generally easier to snag a larger engine than to stroke the smaller one. The regulations on cart racing are a whole different story so stroking an 85 is common. Here's a start http://www.madmanengineering.com/cr80.htm

[fast350]

Originally Posted by greeny250sx

NO AV GAS..never run it..unless its going to be a drag bike and nothing else..av gas is meant to be run wide open all the time..run vp red.

i've ran av gas for years with no problem

[Kane]

You'll get lots of differing opinions as to running AV fuel or not. I myself have run it for many years ice racing with no problems. Proper racing fuel like VP and others, though, will produce higher gains.