250-500cc WR250 power valve adjustment?

[Bench Racer 117]

I am looking for info on adjusting the power valve on my 07 WR250. Is there anything I can do to get more low end power? Is it adjustable? Is it worth doing anything?

Thanks. Graham.

 

[Eurofreak]

There was a thread about using different springs on the power valve-try a search. Pertained mostly to 125's. There is a bolt on Italian piece to make it adjustable but pricey. I would like to have more adjustablility too but it's more effort than I want to expend for researching springs, etc.

 

[letitsnow]

I am looking for info on adjusting the power valve on my 07 WR250. Is there anything I can do to get more low end power? Is it adjustable? Is it worth doing anything?

Thanks. Graham.

I don't think that adjusting the PV on the 250 is an easy task. I recommend switching to the Kiehin PWK carb and FMF Gnarly exhaust (if you haven't already) for low end power.

 

[wallybean]

What Let it snow said... There is a spring kit for the 250 but it won't effect the bottom end. It only changes where the PV's open which will at best give you more a little sooner. It is also a real pain in the ass to change. You will get more bang for your buck with the PWK and the Gnarly.

Walt

 

[Bench Racer 117]

I guess that's out of the question. It's okay. At least I got an answer and didn't waste a bunch of time trying to change the PV and get nothing in return.

I have a gnarly pipe. I do not like it. Talk about making your bike boring. My Doma is way better everywhere.

I guess it might come down to head work getting the right squish for better low end power.

I don't have the means right now to change carbs and from what I've heard, the Mikuni is fine. My bike is jetted pretty well. Riding a KX250 made me realize how much I'm missing. I don't need as much as the KX puts out, but a little more would be great.

 

[letitsnow]

I guess that's out of the question. It's okay. At least I got an answer and didn't waste a bunch of time trying to change the PV and get nothing in return.

I have a gnarly pipe. I do not like it. Talk about making your bike boring. My Doma is way better everywhere.

I guess it might come down to head work getting the right squish for better low end power.

I don't have the means right now to change carbs and from what I've heard, the Mikuni is fine. My bike is jetted pretty well. Riding a KX250 made me realize how much I'm missing. I don't need as much as the KX puts out, but a little more would be great.

My 2000 WR250 with a Gnarly and PWK has more than a KX250 everywhere. I owned a 2002 KX250 before switching to the WR.

 

[letitsnow]

The only area where the KX felt better was in flywheel affect.

 

[letitsnow]

^^^ as in less effect so that it would spool up and down quicker.

 

[Bench Racer 117]

I had a feeling that the KX would wear me out pretty quick. That's weird about more everywhere over the KX. That's not the case with my bike. When I rode the KX back to back with my bike, I had a 2C pipe on. But am most impressed with the Doma.

About the PWK. Is it a worthy switch? How much of a difference did it actually make? Is it worth the cash? Would you do it again? I was told it would help from my buddy whom I purchased the bike from. He told me he spent a lot of time getting the jetting spot on for this area. And I believe him from the way it runs. But can you compare the Mikuni with the PWK?

 

[raisrx251]

There is a way to adjust it and it is pretty simple. Give me this week and I will try to get you a picture of height adjustment. Basically what you are doing is adjusting the height of it and how open the valves are. You can add some pre-load to the power valve spring but like everyone else said I probably would not recommend that. You have to pull the whole side cover off and honestly not sure it helped me too much.

 

[R_Little]

I don't think that adjusting the PV on the 250 is an easy task. I recommend switching to the Kiehin PWK carb and FMF Gnarly exhaust (if you haven't already) for low end power.

Amen, a pwk changes the low end completely

 

[raisrx251]

The PWK 38 did seem to help on my '07 WR 250 as well. The bike did seem smoother with less violent hit. As far as adjusting the power valve height, here is some information that came from either a member here or TT. I am sorry I do not remember who to give credit to. Hope this helps. If adjusting this be extra careful that the power valves are not so close as to rub the piston skirt.

1. Remove seat, gas tank, right side cover, silencer and pipe
2. Remove radiator cap and drain coolant
3. Remove upper motor mount and spark plug
4. Disconnect coolant hoses from head
5. Remove head and right PV cover
6. Move piston to bottom of stroke
7. Measure from bottom of PV to top of cylinder. See photos
8. You will need to improvise an accurate method of measuring. I made a small L-shaped plastic ruler with two marks for the settings I use. The short leg of the L needs to be just long enough to grab the edge of the PV. See photo
9. Make sure PV adjustment arm is bottomed against case when measuring. See photo.
10. Loosen bolts and adjust PV height.


I use 48.0mm for MX. It gives great top end power at the expense of bottom and mid.
I use 50.5mm for woods riding. Good grunt, but not as much peak power or revs.

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[Anthony_1978]

excellent reply raisrx251

 

[Bench Racer 117]

Definetely excellent. That doesn't look to difficult. So just build a L shaped tool, measure 50.5mm, and adjust bottom of PV to correct height. Measure PV to top of cylinder, just like the pictures.

What can I expect? Will I need to re-jet?

Best answer yet. Thank you.

 

[schrode]

nice write-up.

 

[ray_ray]

I always have to reply about how great my C2 racing pipe was when I read questions about the engine performance \ pipe issues on these bikes... Pipes are a big key with 2t engines

From what I have read, 2C pipes are not out there manufactured under this name any more but are available ...

My 02 CR250 was greatly improved over the PC pipe that was on it when I purchased it after the 2C pipe was attached ... The low end was picked up, not like an asian bike that always seem to pull from the very 1st rpm and then not so much at the MID and top, but the engine got on the pipe much quicker at the bottom and was a beast from that moment, thu the MID, and out the top ... Sort of like adding a set of Hooker headers to a v8 ... The engine just opened up everywhere...


That head work is only ~100.00 $ or so ... That might be the way to go and maybe get some ports polished also ...

raisrx251, Are you using the same head gasket each time you go into the head to change this setting?

 

[raisrx251]

Just found this post again. Honestly, sometimes. I had a lot of spare gaskets but if it was recent I have re-used them. Heck one time I ran some Honda bond gasket material as a gasket, it is really good stuff. They sell it in two forms one that gets hard and the other that stays softer. That is a very good deal at RB designs and wish I would have tried it. Been riding four strokes lately. hmmm....might have to bump down the volume.

 

[tony_dt]

They are O-Rings right? They can be reused. The PV side cover gaskets can sometimes be reused. I like using new ones because the only air leaks I have found were at the PV side cover gasket.

 

[raisrx251]

Yes the Head O-rings there is no problem being re-used. I normally kept a new head inner O-ring around though just in case.

 

[ray_ray]

Two O-rings? what is this inner ring? What is on the base of the cylinder?