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View Full Version : Removing Powervalve from cylinder?


gandgracing
06-24-2008, 12:07 AM
Have heard that doing this could be better for what I do( 1 Dir Racing). Can I just remove it then make a plate to cover the hole? Without the valve will it be a more explosive hit?
trx310R#24
06-24-2008, 01:32 AM
what kind of racing do you do
gandgracing
06-24-2008, 02:01 AM
Mostly dirt hillclimbing and some drag racing. The hillclimbs you dump the clutch in 2nd gear at the start and run the same gear to the top. Pretty much a drag race uphill with some breakers in the middle.
C-LEIGH RACING
06-24-2008, 10:20 AM
You can remove it, but you got to make a piece to go in the hole where the valve itself was at, fill in the hole up to the exhaust port.

What cylinder do you have.
Neil
Sparky250R
06-24-2008, 03:59 PM
im no pro but doesnt the PV add alot of torque which would be beneficial in hillclimbing. I could see no PV would add massive flow but I bet too much flow would be no good.

Can you replace it if you take it off??
gandgracing
06-24-2008, 06:58 PM
Its a PC2000 340cc cylinder from Duncan. I have been hearing that you can get more power out of a non-powervalve. My motor is set-up pretty much for all out top end and my valve is set pretty loose so it will open quickly. Just trying to get some feedback to see if its worth the hassle.
All250R
06-25-2008, 11:49 AM
powervalve cylinders are more expensive than non. They have their purpose. OEM's have been putting powervalves on their dirtbikes regularly since the early 80's. If you want to remove that feature I'd consider building a different cylinder. It's kind of a wasteful to remove it.

If this helps, the PV creates a dynamically changing variable exhaust port duration and blowdown time. It's a simple mechanism that lets the motor run best at a wider range of rpm's. So holidng the throttle pinned at peak hp is not using the PV, but just about everywhere else it is. I don't know if smoothing the upper surface of the port will help flow in any important degree, but off the top of my head, A Bell recorded that the PV helped in overall and peak performance in a comparison between a yamaha twin with and without the valve. 2cents.