I just read that an 85 250R ATC had stock HP of 38.
OK, so a Raptor has approx 34, and a Z400 about 32.
I had heard the 86R was the most powerful of the 250R's. Not sure if it's true or not.

My 250R is fast, but not 38 HP fast. Course I have beat the shi+ out of it for a couple of years now.

Just curious if anyone REALLY knows the answer.

Thanks and keep it on 3 wheels!

 

That's likely a crankshaft number... The other numbers you are qouting are typical rear wheel numbers.

My 86, bored, reeds, and pipe isn't 38hp fast - not for what it weighs anyhow....

 

I have seen numbers in the 27-29 range for stock machines.

If you've ridden your machine hard for a few years you should do the top end. The repair becomes much more complicated and expensive when the piston skirt breaks off and gets lodged in the crankcase. Just my $.02.

 

Hey 86atc250R,

I'm interested to know the difference of adding a pipe. Word I get is that it's quite the add on for a 2 stroke. Any insight for me on this?
I mean is the power increase like "Holy Shi+, this thing REALLY hauls now!", or is it more like "Yeah, I could never quite climb that hill before my pipe" kind of power?

 

I was impressed with the difference simply adding my FMF pipe made... Completely changed the attitude of the engine & gives it that signature tinny race 2 stroke sound.

I guess I would say, the first time I rode it after putting the pipe on was more the "Holy Shi+, I wasn't expecting that much of a change" response.

 

stock HP for an R is 22 I believe.

 

If you want Holy Sh*t horsepower, PM me in a few weeks. I'm almost done with my ground up rebuild of my 85 ATC250R with a 350 powervalve jug set up for race gas. I'll let you know how it goes.

PS-this project has been overschedule and overbudget.

 

Explain the mechanical intricacies of a Powervalve. I've heard this before, but do not know any details. 350cc huh? You putting an extended swingarm on that guy??[img]i/expressions/face-icon-small-wink.gif[/img] You will need it.

 

The powervalve used in this instance is a Ski-Doo,Sea-Doo RAVE valve. The valve is set to raise at a certain RPM which is tunable by varying the spring pressure of the valve assembly. The benefit that you derive from this system is that it effectivly varies the hieght of your exhaust port. Low RPM=low exhaust port hieght and great low end power for a 2smoke. Higher RPMs make the valve open which raises the exhaust port height for more flow and lower compression which allows the motor to make big power through good mid-top porting or even drag porting to some extent. So in a nutshell, it should pull like a tractor and rev to the moon.

The cylinder is imported by LA sleeve and made by pro-x. There are only 4 piston sizes available but it is a sleeved cylinder so it is completely rebuildable. The 350 does require that you have your engine cases modified to accept the larger cylinder, but it in no way affects your ability to return to the use of the stock cylinder. This cylinder is similar to the smaller pro-x cylinders in that it has a modern port layout and has improved cooling over the exhaust port and features an O-ring head with different size domes for the head to allow you to experiment with different fuels if you have the desire. I'm just going to leave it set to run well on Unocal 110. It should make 60+ at the back tires. I'm going to break it in with the STOCK swingarm and ride it once that way just to get a feel for how long I'm gonna have to go. I'm thinking +5 and +4 on the axle. I don't mind the wheelies(I ride a YZF426 when I'm not working on this damn thing).

 

Great Info! Thanks!

Sounds intensly INSANE!!!!








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