Horsepower and 250's

[Expat]

What were the likely correct/true horsepower of the last pre powervalve 250's??.....early 1980's

[Hoony]

hard to say but i would be thinking somewhere around the 42-45hp mark at a wild guess

[asasin]

Why Expat ,do you want to join the pre 86 men?Pre 75 too slow for ya?, Ask Shane at the weekend his 250 cr leaves the rest of us in a straight line like we have put the brakes on!!!

[JC]

Expat,

Lozza would probably have a fair idea.
My guess would be a bit below Hooney's, but I'm only guessing too.

[mx250]

Showed Lozza my 9 port reed valve Monty barrel recently....



...and he reckoned 50hp . Probably 'at the crank' . Whatcha reckon, 40-45 at the back wheel.

And that would everthing being spot on; best ign, best fuel, best carb, best tune, best chamber  . But not bad, a 50% improvement in 10 years, early 70's to early 80's.

I might have to put it together and find out.

[JC]

Graeme,

Ain't there 10 ports in that Monty barrell? 3 ex, 4 tr, 1 in, 2 boost.

[Lozza]

With water cooling around the 35HP mark.

[Rossvickicampbell]

according to Mugen my 1980 CR had 36 HP and the kit added another 4 to take it to 40.

cheers

Rossco

[JC]

I'm w Loz. I think the other claims are overly optimistic. Factory claims are notoriously optimistic.

A Graham Bell (in his 2stroke tuning book) put a 79/80 CR250R on the pump & got 29.8hp stock, but he upped that to 32.4hp w a three satge diffuser/tapered header pipe, tho its not exactly a fatty pipe.

Seems to me the exh valve was the quatum leap in obtaining hi power outputs in the mid-hi 40s.

[Lozza]

Ignitions and carburetors went ahead also.Not to mention Nikasil barrels..............but todays 250 pump big torque numbers which is where it's at.