250-500cc Power valve control

[MOTORHEAD]

I really like my 250, but I'm understanding why the WEC guys use the PROVINI PV adjusters. All the years they've been building this motor you'd think they'd played with the ramp, balls and spring of the PV governor and get a little better control of the step in the powerband.

I don't really call it a hit, but more of a strong transition for low to high, and the mid gets jumped over, almost.

I've printed out the PROVINI patent and I'm going to study up on it and see if I can figure out just what he's covering with the patent. Then I'll see if I can figure out a way to build something that gets around it, but still gives us the ability to tune the valve opening.

250 / 300 owners interested in something like that?

 

[rasputin]

why don't you just go buy a provini valve? he (tullio provini) is a very nice guy, a race mechanic with a lot of passion and experience. his valves are produced in very small quantities, and he offers full support to his customers.

r

 

[ARod2000]

250 / 300 owners interested in something like that?

well, since you asked I'll answer - No. Not to be a troll or thread downer but I like the power delivery of mine. I love racing on single track and I've never got in a situation where the power caused me to go off line. I'd sure like to ride some more WR's as it sounds like there are some pretty significant differences.

 

[MOTORHEAD]

I'm not sure how to get a Provini controller and I understand they are super expensive. I'm thinking of something a little less elaborate.



ARod, no problem. Everybody's entitled to their opinion.

 

[Motosportz]

I kind of like the dual personality motor as is. Softish bottom for lugging up hills, rip on top for passing, works great. It would be cool to have an adjustable PV though.

 

[MOTORHEAD]

Yesterday I was racing in the rain and it was tricky when it jumped into the "rip on top for passing", with the slick conditions. In those conditions a mellower transition would have been welcome.

A programmable servo would be totally cool. Honda almost got it right, but they screwed up the exhaust port and added the servo. If they'd have left the old style port / power valve design and just added servo they'd have hit the mark, even with the case reed.

Don't get me wrong here, I love this bike and I had more great results with it. I just never stop trying to make improve things. I've been working in R&D most of my life and it's just the way I am.


I guess your '93 runs pretty much the same way?

 

[Dirtdame]

You could always get that softer transition the old fashioned way by using a flywheel weight.

 

[Motosportz]

I guess your '93 runs pretty much the same way?

94, and yes, similar. Rode it back to back with a very hard running 07 with a pipe. The 94 has a little more bottom, maybe a little more mid and less top. Way more flywheel effect though. lug it around all day or let it rip. The 07 spooled up a LOT faster and was more spunky. Not sure what i liked better. The 07 feels real quick / fast but the 94 is very smooth controllable and just as fast or faster, just does not feel as fast. At first I was thinking of getting a lighter FWW for it now i think i will leave it as is.

 

[robertaccio]

added info

why don't you just go buy a provini valve? he (tullio provini) is a very nice guy, a race mechanic with a lot of passion and experience. his valves are produced in very small quantities, and he offers full support to his customers.

r

http://www.officineprovini.it/eComShop/eComShop_viewItem.asp?idProduct=5106


i believe TMs come with Provini valves, FYI born on 2 stroke with PV road racers

 

[MOTORHEAD]

Thanks. I don't know Italian, but you think he'd deal with a Yank?

 

[rasputin]

he speaks excellent english, and he's a very friendly guy.

r

 

[MOTORHEAD]

You could always get that softer transition the old fashioned way by using a flywheel weight.

"From the mouths of babes."

I've considered that, but the 250 already feels a bit on the flywheel heavy side, for my taste.

 

[MOTORHEAD]

he speaks excellent english, and he's a very friendly guy.

r

That's cool, thanks.

 

[lookin4trails]

"From the mouths of babes."

I've considered that, but the 250 already feels a bit on the flywheel heavy side, for my taste.

Of all the places I would spend money on a WR, a power valve and / or flywheel weight would be pretty far down on my personal list.

Have you considered trying a throttle cam? I've got one on my WR - it enables me to ride in snowy / muddy grease and still modulate traction.

 

[MOTORHEAD]

I know, but I'm afflicted with a disease that makes me do these things. I'm sorry.

 

[raisrx251]

Don't worry Motorhead, I did the same thing about two years ago with my WR. Once you stop you end up selling it and being bummed..

 

[wallybean]

+++1 to what raisrx251 said. I let my nephew talk me out of my 06 WR250 and I really miss it already and it hasn't left my garage yet. 04 plastic, seat, and tank, 6 speed, rekluse pro, plated, ACE suspension(sorry LTR, but this is the most plush suspension set up I have ever ridden)airstriker PWK, fmf gnarly and turbine core II, and absolutely rips everywhere. If my WR125 wasn't so light, flickable, and fun to ride I might give him his money back and deny access.

Walt

PS. I have an LTR revalve in my WR360 and it is good, just not nearly as plush as the ACE suspension revalve. They have really nailed the 45 zoke setup.

 

[2stroked]

You could also try a G2 throttle setup, I have one for my bike for winter riding, it slows the opening of the slide, works pretty well in slick contditions

 

[raisrx251]

Have you played with the height of the power valve at all? I also wanted the Provini and ended up making a washer to pre-load the spring. Not sure if it made that much of a difference.

 

[MOTORHEAD]

No, I haven't. I looked at it pretty hard when I had it apart, but haven't tried anything yet. I was thinking of raising the closed stop a bit.