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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc.


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Old 04-21-2011, 04:46 PM
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Default Powervalve issue?

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?


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Old 04-21-2011, 06:53 PM
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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.
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Old 04-21-2011, 07:00 PM
stemplin stemplin is offline
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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.
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Old 04-21-2011, 07:47 PM
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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.
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Old 04-22-2011, 05:16 PM
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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.
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Old 04-22-2011, 06:13 PM
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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.
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Old 04-23-2011, 02:35 PM
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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?
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Old 04-23-2011, 05:35 PM
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Quote:
Originally Posted by toolmaker View Post
Also the shaft that the bearing is mounted to has threads but no nut. Is that right?
No nut required on the left side.
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Old 04-23-2011, 05:38 PM
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Quote:
Originally Posted by toolmaker View Post
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.
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Old 04-30-2011, 12:04 AM
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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 !



Jeff
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