250R Powervalve vs True powervalve comparison

[250Renvy]

I'd like to hear from people who have 250R powervalve motors or have ridden powervalve motors as well as LT250R powervalve motors and/or Tecate powervalve motors or CR250 powervalve motors.

How does the 250R powervalve compare to these as far as ride and power characteristics?

Most of the 250R powervalve motors are based on the rotax style method of engaging, is there any real difference to the other powervalve motors out there?

[250rPRIDE]

all depends on your riding style, if you will like a powervalve, personally i am a light guy and can run a bike with lots of top end, and i never really liked or had the need for one, but a powervalve bike is a blast if you ride all woods or mx, they hit hard when well tuned. so it all depends..

[red88r]

Both of my younger brother's had powervalve motors for mx. One was a Duncan 265pv-the other a LRD 265pv. Both ran great. At the time I had just a stock cylinder ported and it was good but nothing like theirs. You were able to lug them a bit more and they seemed to get power to the ground better. I don't know if there is any diff. to the other powervalve motors out there though. I know like on my dad's Duncan 340pv you can adjust the spring in the valve to tune it how you like. I love riding a powervalve motor.

[machwon]

Most of it depends on the application you're going to use it in, MX or woods and what the rest of the set up is. They definetely make a broader range of power, but lessens it to an extent on bottom so the power is more managable. It's also easier to tune or make more usable power for the technical mx/woods type courses. Non PV motors are a lot cheaper and can make just as much power, but without the flexibility.

For the Tecate and the KX250's I've done I really preferred them with the powervalve open all the time. Like 250R pride says, I'd rather be working with too much power and controlling it with traction, set up and/or clutch and throttle position. None of the guys who ran the set ups I've done with the powervalves pinned wide open all the time never once complained on these builds. The CR's respond much better with their pv system but if you want a duner or top end power the timings must be raised with these ones.

[250Renvy]

Thanks Bob,

I'm looking to compare whether the 250R powervalve is essentially the same thing as a factory built powervalve - or is it less effective and not work as well? Also is a LT250R, Tecate or any dirt bike with a powervalve have the same characteristics when built the same as a powervalve 250R cylinder since you couldn't really compare them to a non-powervalve 250R cylinder because virtually all 2-strokes are powervalved except early versions of dirtbikes.

[dynofox]

I don't have experience with any of the quad or dirt bike power valves but I am very familiar with the rotax valves as my ski-doo snowmobile uses them. They are very simple and easy to clean / remove. There are actually some aftermarket sled shops that have conversion kits to replace Arctic Cat's cable operated power vavles with the rotax setup. I honestly could never figure out why the rest of the manufactures didn't use this style to begin with, works great and is simple.

[machwon]

Originally posted by 250Renvy
Thanks Bob,

I'm looking to compare whether the 250R powervalve is essentially the same thing as a factory built powervalve - or is it less effective and not work as well? Also is a LT250R, Tecate or any dirt bike with a powervalve have the same characteristics when built the same as a powervalve 250R cylinder since you couldn't really compare them to a non-powervalve 250R cylinder because virtually all 2-strokes are powervalved except early versions of dirtbikes.

Those are very good questions 250Renvy. I think the RAVE powervalve systems is the best you can get on the R cylinders (I'm also ski-doo biased as "machwon" is from my 98 ski-doo Mach 1 sled). Whether they work well or not really depends on how they are set up and in what combination with other parts, porting, etc. The worst a powervalve can do is open too late cause a bog or hesitate until the rpms increase. The RAVE versions are also easier to modify when porting and such. On the new CR's with the RC control system I actually made some limiting devices to keep the valve from closeing too far after porting.

I'm not familar with the LT250R powervalve but I think the tecate were too mechanical and created too much lag time and thus the ones I owned tended to hesitate. The fix for me was to pin them wide open all the time.

[jon370r]

The LT250R power valve is a drum roll that would rotate with engine RPM mechanically to open a small chamber at the bottom of the exhaust outlet on the front of the cylinder. The chamber would act something like a catch for the returning pulse wave, changing the way the pipe and porting worked together (power band). In my opinion it didn't work very well. The CR250 cylinders would block off the upper portion of the exhaust ports there by changing the actual port timing; much like the RAVE valve but it was also done mechanically by the engine RPM. It worked well and could definitely tell open from closed.

[machwon]

Oh yeah, I forgot about the LT's. Yes I agree they were useless.

[rrguy]

The kawi Kipps is suppose to be a good powervalve setup. It is like a 2 stage powervalve were one set opens then both as the rpms raise. I only have rode one on the kx500 hard to compare cause well that motor has lots of low end & is a 500cc single vs a 250cc etc.. single but vs the cr500 the motor has much better power deliver.

the rotax design is simple & seems to be effective.

I had a gasgas 300 with a powervalve & had great low-mid power with great top end & got better with a larger exh valve cover.

I just got a esr 265pv motor but something is not tuned right cause it sucks right now