Powervalve issue?


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Hi guys,
We're having an issue with a 2011 EC250 (my girlfriend's bike). When we picked it up in March, the bike ran great. It pulled strong from the bottom all the way to pinned. All was well, but now the bike is really soft on the bottom then hits very hard in the midrange and pulls well through to revved out. At first I thought it was jetting, but after playing with that it seems to be lying somewhere else. A few people have suggested I check that the powervalve isn't stuck open, so I did.

The powervalve isn't stuck open and seems to operate okay. I did notice that when I had the idle turned up and the choke on, the powervalve mechanism flutters (actuating plate behind the right side cover rotates approximately 60 degrees clockwise). Once the bike was warmed up, the powervalve remains shut at idle but as soon as I twist the throttle, it opens about halfway, then at maybe 1/3 throttle the powervalve is all the way open.

To me, it looks like the powervalve is opening too soon. Any idea what RPM it should be opening and how fast it should open up?
I'll bet I know, sounds like my '03 was. Soft low end and a lot of rattle. The bellcrank setscrew is either loose, or the main adjustment is off allowing a large amount of free play in the mechanism. What is happening is the PV itself is just floating around under pressure of the exhaust pulses. You need to pop the side cover off and adjust out all the free play. Everything else in the PV system is set by mfg tolerances.
This sounds like the same sypmtoms my 08 is having. Can you explain a little more what you mean by the bellcrank setscrew and which side cover you are referring to.
My 2011 has the same symptoms. It's been that way since new. I thought it was jetting also, but I've pretty much got it running strong.... all but the bottom end. I guess I didn't think about the power valve. Please explain what to look for and how to adjust it if that is indeed the problem.
To get the free play out, do I need to shim the spring or adjust the position of the actuating arm coming off the governor? I checked and there's no loose screws in there.
Hold/jam the PV actuator plate up on the cyl closed.

Preload the PV governer spring with a .005" to .010" feeler gauge (not that critical). I used to do it by feel but this is easier and consistent.

loosen the setscrew on the bellcrank

Push/hold the governer assy fully into the case bearing, be sure its straight, and
tighten the setscrew

Remove feeler gauge and replace the side cover

The idea is to remove all freeplay and end up with just a VERY SLIGHT preload, so the actuator is held to the stop.
I took the side covers off and started the bike to see what happened with the linkage. On the left side the bearing moved in and out about 1/8" at idle. Is this normal? Also the shaft that the bearing is mounted to has threads but no nut. Is that right?

On the right side the actuator seems to open at the right time. I'm going to guess about 5000 rpm. With the engine off the plate is not touching the stop. About a 3/16" gap. I'm not clear on the advice to preload the spring. Do you loosen the bolt that the connector from the bottom is attached to? Do you push the plate up or down against the stop?
Also the shaft that the bearing is mounted to has threads but no nut. Is that right?

No nut required on the left side.
I'm not clear on the advice to preload the spring. Do you loosen the bolt that the connector from the bottom is attached to? Do you push the plate up or down against the stop?

The transmission right side cover has to be removed to access the power valve actuator.
While you're in there, take out the preload shims, if any.
I think you'll like it ! I sure do. It's counter-intuitive that the power
valve will open sooner, for "better" low end, but it works !

I saw this thread this morning and this is what I came up with to take up the extra 'slack' in the mechanism. I only took off the powervalve cover, and didn't fool with taking the transmission cover off.

I made this from a small spring I got for $.50 at the local hardware store. I cut a small notch into the powervalve shaft with a Dremel. I then looped the end of the spring around the allen bolt. The spring tension itself is very light and only keeps the shaft from flapping around. Hopefully it won't delay the valve opening by much if at all.

I will report back in a few hours after a test run.


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Test ride done: It was ok......

It delayed the hit a little longer then it hit harder.

The powervalve was quieter.

The spring popped off toward the end of the ride.

If I need to JB weld it into the slot for the day in the trails to make a full determination.
That's interesting. Maybe it might be easier to do something similar on the RH side - more bits to attach a spring to... you've got me thinking now!
On a second note, anyone realize that the bearings in there are interchangeable with rollerblade and skateboard bearings? :D
That is not the same thing at all as far as removing free play. You adjust the free play out as discussed, and then play with PV shims if desired. What you did is what the Trusty PV cover does, in one direction.
Just to be clear, if someone wanted to adjust shims and free play, they would need to drain the coolant, remove the pipe, take off the water pump, clutch and transmission covers correct?
Yes, you have to remove the primary side cover, but if your actuator plate is on the stop with the engine off then there is no need. If the plate is off the stop, there can be excessive movement and rattle, and in severe cases a softer low end as the PV is open slightly. My '03 was way off like this, but it is rare.
OK< as of this morning, I looked at both sides after taking the pipe off. On the right side where the hook/arm comes up and works the valve, there was a little triangle piece that was next to an allen bolt stop.

The valve was not resting on it, but was hovering about 4mm away from it. I could look into the exhaust port and by working the mechanism a little I could get the valve to move further toward the piston and the triangle piece to hit the allen. If I let go, it opened back up again.

So you would recommend me take the case cover off and shim this up so it stays closed? I do have a noticeable rattle in the lower range when accelerating slowly.
That is exactly what I'm referring to, and you can correct it with the adjustment. Its an adjustment of the arm in the mechanism on the shaft via a setscrew, not a "shimming". The "triangle piece" is the actuator plate.