Has anyone heard anything about Duncan racing modifying a CR cyl to a 250R and have the power valve work ? Or any other company that may have done this?Does it create alot more HP and how muh work is needed to be don to the cases?

 

Try FTZ Racing www.ftzracing.com they have built several variants of this hybrid motor.

It offers some very worthwhile benefits. Better port design and layout, and better cooling(most likely thier claim with their "Dyno" head).

Worth a look.

 

I cannot answer this directly but I will tell you what I know. Travis Spader showed up at Loretta Lynn's this year with a motor in his 'R' that has a power valve. I never did check it out up close but from heresay, the motor is a completely new experimental unit of Duncan Racing. As far as I know it is not a CR 250 cylinder but something like a Niks that Duncan is having made special. After that I never heard anything else about it. Might want to consider giving them a call but then again they might not tell you anything.

[This message has been edited by bpace (edited 01-12-2000).]

 

TRAVIS SPADERS CYLINDER HAD A POWERVALVE THAT IS USED ON SKI-DOO SNOWMOBILES IT IS TUNEABLE BY CHANGING SPRINGS INSIDE THE VALVE IT LOOKS TRICK BUT I THINK HE HAS THE ONLY 250R BASED CYLINDER EVER BUILT

 

I got a few pics of Travis' quad at Lorrettas, but at the time I didn't know he was runnin the trick powervalve cyl, so i didn't get any motor pics. ATV sport had some shots of the cylinder a few months ago though. It looked like a Pro-X cly, but with a powervalve off a Sea-Doo.

 

I take that back. I did get a picture of part of the motor. Its not a modified stock cylinder, and it isn't a Pro-X or CR. Must be a custom job.

 

I saw the same power-valve setup on a chainsaw on ESPN. Very trick, and I want one!
I wish that kind of stuff would trickle down to us normal people. Every time I ride my brothers '99 CR250, I spend hours trying to think of a way to get that motor in my TRX250R. Maybe someday we'll get power-valves too.

 

Some guy invented that cylinder/powervalve set up for a snowmobile. Duncan Racing is trying to buy the rights to it. Sounds like a monopoly to me.

Anyway Duncan use to make a real fast set up using a CR cylinder and welding the powervalve. I think it was the only fast cylinder the ever produced (tee hee). Sorry Loren. The powervalve Travis used seemed to work pretty well. Although he did drop very far back this year in the 250 Pro GNC's. Better luck next year.

The only problem I see with a powervalve system is... A powervalve is use to make the bike rev more on top. Quads need allot more low end power than a MX bike. So more high rev power seems kind of useless to me.

To answer your question no modification to your cases are needed to add this powervalve. It is not linkage actuated it is activated by the gasses in the exhaust.

Waymod

 

That's an advantage of a power valve, at the least the exhaust port guilateen(sic) type. The power valve allows for a motor tuner to set up the cylinder to provide greater low end power via different port timings. However, as RPM's increase the valve slides back, effectively opening the exhaust port to a larger dimension, greater port timing and duration, which increases top end power. The greater port timing and duration are more favorable to those higher RPM's. So in essence it allows you to run low end porting, but...still have that great screaming road racer top-end.

 

you guys need to search. the cylinder was made by psi. they also make a head with screw adjust compression. way trick stuff