What's your opinion on power valve engines?

[Derrick Adams]

I just picked up an 87 YZ250 engine for my Tri-Z. From what i've read this is a great power upgrade. My concern is whether it's going to work on the trail or not. Most people I see doing this upgrade are into drag racing. Granted, I'd like to have a faster bike however I do an awful lot of hill climbing and need all the torque I can get.

Everything I read on this engine is conflicting. Some say that the power valve system is designed to improve low end and midrange without sacrificing top end and others say it will hit so hard in the mid range it will pull the bike out from under me.

I definately don't want to lose any low-end. So I may or may-not use it.

What do you guys think?

[Flattrack]

Ya ya Listen to every one else I'll buy it off you.J/k It's a great up grade When set up correct it will give you smooth power all the way through. you'll loe the power valve for the hill climbing. The power valve is designed to help out with exhaust timing and create power through the whole RPM range.

[racezilla500]

Yeah, the powervalve will help your exhaust to give you the "on the pipe" feeling at lower RPMs. Take two exact machines....one powervalve functioning-one not....both machines tuned exactly the same...the result should be that the powervalved machine will pull the holeshot every time. Once out of the holeshot, it doesn't matter much....until you come to a corner and drop RPMs again. USE IT!!!! I can't figure out why there isn't a powervalve on every pinger. If someone can tell me why Yamaha didn't incorporate a powervalve in the Banshee... I'm all ears! I do know that there is nothing like that explosion of power though, so maybe that's why they left it out!

[Derrick Adams]

This is what's got me wondering. Read this.

http://www.3wheeler.org/3wheeling/12-84~pg38.html

I do wonder if their situation was due to the pipe and set-up.

[spdygonzalez265r]

from what i have heard, a power valve motor is good power all over the RPMs. it is used a lot in MX bikes b/c the power is smoother and easier to control. i was looking to do the powervalve to my R and many people said that you will kind of lose the "HIT" that the 2 stroke gives, but you will have the power all over. when i re-do my motor(later on down the road) i will do a powervalve kit on it.

[racezilla500]

Well, it kind of sounds like that article was a hack & whack attempt. They used a pipe designed for a specific motor on a "collage of parts" motor. Really, I'm not surprised in what they are saying.
A powervalve is designed to cease operation at a specific RPM setting, say 3000-4000 rpm, allowing for non-interrupted mid to high end power. Once below that set rpm, the powervalve is actuated again...diverting your exhaust through a chamber, which in all reality supplies more backpressure for low end power.

[370banshee]

hmmm well i have a yz powered tri-z but i'm no help haha mine drag ported on booze
but i can help you through the swap

[370banshee]

thats a cool atricle

[terboed]

use the damn powervalve motor. its not as intense as people make it too be. you just have to be able to ride it.

[Flattrack]

That was a waste of good paper ......If you ran out of poo paper and had to wipe your ass ,That article would be a good substitute......