125-200cc 125 power valve adjustment - again

Ok another dumb arse question -
Kelly & others have described adjusting the power valve nut all the way up on the Wr125
The bolt is in the middle of the hole in the main outer arm
The outer and inner arm appear to be stuck togeher and undoing one bolt does nothing
Do you have to adjust the smaller arm by undoing the other bolt as well
this main bolts is hard to loosen as it turns the linkage
Are there any issues if adjusted all the way up
Help appreciated
cheers































bolt

You have to loosen both bolts. Push down on the arm to get the bolt all the way to the top, then snug either of the bolts to hold in place while tightening both.

The only downfall of adjusting the bolt all the way up seems to be a small loss of top-end power. But the trade-off for huge bottom and mid gains is well worth it. Walt has stated you can back the screw off to about 3/4 from the top and lose hardly any top-end while retaining the benefits of adjusting the bolt.

I have tried all the way up, 1/2, and 3/4. It is very hard to tell the difference between 3/4 and all the way up. At 1/2 the bog starts to creep back in on my bike.

Adjusting this, and getting your jetting correct will make a huge difference in the amount of power and spread of power the little bike has. It will chug up hills and surge through the mid-range with a nice strong linear top-end pull that seems to never rev out. Very fun.

JS

cheers -I am excited already

And I can imagine adding the 144 kit to the PV adjustment and PWK is really close to perfection in a dirtbike.

JS

Still seems soft in the mid range - hits a bit harder but hard to tell going around the block - bike not really warmed up
Mikuni has still got to go...

Order the power valve springs from Wally before going 144. I'm pretty sure it's all this bike needs.

You guys are making me want to adjust mine on my 08 CR125. Any pics of this floating around? Thanks.

So I have been wondering something. Is the source of the 09 bog the factory not setting the power valve correctly, or is it that when the dealers installed the updated parts they did not always put them in the right place? If it’s the former that would explain why the problem is not found on all of them and why it was not an issue on previous years.

If you look at the very top right of the picture you can see the edge of the upper spring that allows the linkage to move more than the pv's themselves. This spring has very little tension initially. With the linkage adjusted as it is in the picture there is very little pre-load tension added to the system from the governor. This lets the power valves occilate with the exhaust pulse at certain rpms. When you take your pipe off to do the adjustment reach your finger into the exhaust port and move the power valves. It was surprising to me how easily they can be moved that initial .1" which is more than enough to cause issues. That spring also becomes fatigued with age and looses even more of its tension. Gestion actually had his break. The power valves themselves are much narrower in cross section than the pre-09 125's. I don't know how this affects the operation as everything else is the same.

As far as changing governor springs, first try adjusting the linkage and just pull the trigger and install a pwk airstriker. Then if you want to be able to change engagement rpm's and progressiveness try the spring kit. The thing to remember is that when you adjust the linkage up you are pre-loading the governor spring and this allows it to open earlier. So you will have to go up one stiffer spring in the kit to get the opening rpm up to be the same as is listed on the instructions.

Good luck,
Walt

Looking at this last night while changing the pv spring, it seemed to me that if you go too far in the adjustment slot it will put too much pressure on the little spring. That's why mine broke. 1/2 way I figure it works best without excess pressure on this spring. It gives it a very slight pre-load.

The big spring in the power valve is where there is worthwhile adjustment to be had IMO.

Thank you very much for the pics.! I will check mine and adjust to the top to see what happens.

Kelly,

When you adjust the linkage up it compresses the governor spring and in doing so allows the governor ball bearings to circulate at a greater distance from the center of the shaft and it results in them spinning at a much higher speed and thus creating a much greater moment of inertia(centrifugal force in this instance) This greater force compresses the single rate spring at a lower rpm. When you used the lighter springs this happened even faster and the less pre-load the more they occilate and the more you pre-load the faster it dumps open. If your upper spring is at all fatigued this exacerbates the whole process. Remember how hard it is to compress the stock spring and now think that there is only 200 rpm difference between when the spring starts to compress and when it fully compresses with no pre-load on the spring. It just illustrates how much the centrifugal force increases with distance from the center shaft. Also the governor is spinning at 1.2 times the crank rpm. 5000 rpm crank speed = 6000 rpm governor speed. The strength of the governor spring is almost irrelevant once the balls circulate at a sufficient distance from the central shaft.

When I get my forks back from Les at LTR, I will get my laser tach out again and give you some actual numbers on the linkage adjustment and rpms. It will be interesting to see if all this blather is backed up by actual observed numbers. I know that I definitely had to go to a stiffer spring to get the pv's to open at a much more rideable ~5500 rpm than the ~4000 rpm it was dumping at when I adjusted the linkage the rest of the way up.

Walt

So Walt sould I adjust mine to the top (08 Cr125) ? I like bottom/mid power.

John,

Adjusting the linkage up doesn't effect how your bike is meant to run at all. All it does is gaurantee that the pv's stay completely closed until you reach the rpm that the centrifugal force is enough to override the spring in the governor. Not allowing the pv's to move or occilate early creates the intended bottom and mid-range that Husky designed into the bike. Your 08 CR125 has the exact cylinder that the 09 WR 125 has, so all things being equal yours should run exactly like Kelly's. The problem is that you don't have a doma pipe, and I am not sure that the digital CR ignition has the same timing curve that the analog unit on the WR has. I would think that with the significantly lighter flywheel weight of the CR that it should run even better than the WR if some what more prone to stalling. If you are looking for more bottom and mid-range than you get by adjusting the linkage up, I would definitely consider the 144 kit. I haven't heard from any one that has the oem kit but the rumor is that it makes great low end and mid-range power. That would be the way I would lean if doing it again and you also get the factory modified PV's and that is no little thing. My 144 came alive on the very bottom end when I did a little die grinder work on my power valves. The currently offered kits don't do this and the re-grinding for clearance with the larger bore actually lowers the exhaust port from stock and robs you of some low end/mid-range.

Don't know that I helped at all,
Walt