Enforcer is right. I owned a 89 kx250, and it had a power valve. The powervalve closes somewhat at lower rpm's making the motor think it has a smaller expansion chamber on the pipe {good for low, mid power}, at higher rpm's the power valve opens fully, letting the motor "see" the full expansion chamber of the pipe. The power valve tricks the motor into thinking it has a smaller pipe at lower rpm {good for low mid power} than it actually does.

 

Right concept you just have it backwards... a power valve works by effectively varying the tuned length of the expansion chamber. The longer the expansion chamber (power valve open letting exhuast into some sort sealed cavity atached to the cylinder or between the cases) the more low end / midrange you will have. As the power valve closes it dirtects the exhuast right inot the pipe effectively shortening the tuned length of the expansin chamber.


as far as 2 stroke quads (from the big 4) that came from the factory with power valves......... LT250R, LT500R, Tecate 4

 

WOW dumb post

 

Yup, this dang post is going to end up costing me money if I'm not careful. I've owned half a dozen CR500s over the years, and have always thought they had the all time best powerband ever made. Four strokes are fun, but they just can't replace that instant hit of raw power that a two stroke has. Here I was all happy with my KTM 525 MXC, other than the fact that it is a bit too heavy at 249 lbs., and sometimes you cant get it to lay down like you want it to in a turn, because of the high center of gravity from the four stroke engine. I had already thought about getting a YZ 450F this fall because they are 29 lbs lighter than my KTM, and have a little better handling. But then I get to thinking, ... hmmm, ... a brand new CR500AF with the fourth generation aluminum CR250R frame would weigh just 213 lbs, which is a whopping 36 lbs lighter. I just fired off an e-mail to Service Honda asking way too many questions. I wouldn't mind owning a CR500 again, LOL.

 

I have a 93 KX500 and it DOES have a powervalve. The bike kicks ***. Its mean as hell.

I did have an 88 Zilla, and it did have a powervalve also. However, the KX motor is much much much better than that Zilla motor ever was.
More power, (obviously less weight contributes) rock solid reliability, and I cant speak highly enough about the KX500 motors reliability.
It is IMO one of the greatest bike/quad motors ever. Its power/torque and reliability are second to NONE.

The Zilla motor... power and reliability considered, crap by compairison. (no offense to Zilla owners, the KX motor is way more 'alive')

My brothers 86 Qracer 250 does not have a PV.

The banshee is one of the worlds great 2 strokes, IMO. (possibly the greatest... being the only ATV twin 2 stroke)

 

[img]i/expressions/face-icon-small-smile.gif[/img]


I always thought one of those would be sweet. If I was younger I would love to get one. My 400 Exc is so sweet in the woods and takes about one third the energy to ride.My CR500 right now has a paddle tire pretty much permanently mounted to it. It goes to pismo dunes every july. Its sort of in semi retirement.

 

The Banshee...

 

Even though they don't come stock with alot of power, once you get some upgrades, the blaster is one of the most reliable 2 strokes i know of, mine will start up on the first kick even when its cold most of the time. Maybe i'm just saying this because i have one. The thing with the banshee (and don't get me wrong, i love banshees) is that i know a ton of banshees that have so many problems starting its pitiful, and i've never seen a blaster that was hard starting even. And there are some really fast blasters that could smoke banshees in a drag race (see pics). But this is the kind of forum that gets so many fights riled up because its too open ended. Anyone could bring up a good point about any 2 stroke to dominate over all the others.

 

Ummm yeah well that blaster might keep up with a Banshee running on one cylinder with a fat chick on the seat.................[img]i/expressions/face-icon-small-wink.gif[/img]

 

banshee hands down.. it can smoke basically anything when modded right.