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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc. |
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#1
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Power Valve Removal
After 100hrs of flawless running my 2006 300 did an odd thing. While running the road at a good clip the exhaust note suddenly changed and the next thing you know the engine is locked up and the back wheel is skidding. In with the clutch and pulled over expecting it had seized, but found neutral and it kicked over fine with normal compression, but when it started it was rattling like a SOB. Sounded like a piece of metal rattling inside the expansion chamber. DNF for the first time.
During the teardown I'm expecting to find a broken clutch tab, piece missing from the piston, or something obvious.... nothing. In fact, the clutch, cylinder and piston all looked in great shape for approx 100hrs use. What I did find was something possibly odd with the power valve. When you hold the flapper stationary, you can grab the lever plate (the part that the actuator rod attaches to) and move it about 15-20degrees without too much effort. Should this not be one rigid piece ??? I would think thats whats causing the rattle, but I still don't see any indication of where anything hit together to cause it to lock up. (no marks on the piston or flapper) I'm trying to remove the whole pv assembly now and I've pushed out the one rod that is under the allan bolts that hold down the bearings, but I can't pull out the stupid pv assembly on the right side. Any tricks to get it out ? or any idea what could have happened ? |
#2
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Have you pulled the piston out to check?
That really does sound like a seizure and yes they often do start again and the compression "feels" the same at the kickstarter. I have had exactly this happen to mine. I had it jetted lean to stay clean in tight woods (which I forgot about) but one day was riding down the road at about 50 mph and the symptoms were just like yours. The moment I stopped it was locked up but it kicked free and started. Although there was no rattle on mine but hey anything could've happened. I rode it back no problem at about 20 mph but as soon as I pushed it on a bit it would nip up again. On disassembly it had clearly seized. |
#3
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Yep. Piston, rings, wrist pin and bearing are fine. The cyl still has a fine cross hatch everywhere with no scrapes and only a few very fine normal looking scratches that you can't even feel with a finger nail.
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#4
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Sounds like a crank main gone south.
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#5
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Don't think so, it spins without any rumbling or roughness.
There was a change in exhaust for about a min or so before it locked up, which leads me to believe that its something with this sloppy power valve. Can someone confirm something for me ?? If you hold the powervalve flapper stationary in the exhaust port, should you be able to move the lever plate at all ? There is a 15-20 degree movement there, and I can't seem to pull the assembly out of the right side. Any tricks to get it out? I have the pivot rod out (the one behind the allan bolts), but I can't pull out the assembly on the right side (step 9 in the instructions posted by MattR) |
#6
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cdn,
That sounds about right to me (the play, not your problem). The flapper has a slot at an angle, and the rod between the two drums rides in this and forces it up and down. There isn't a whole lot to go wrong. There will be some slop even between the two drum valves. The flap should not be able to hit the piston and did not in your case. To remore the right side drum, thread an M5 bolt back in the drum and pull it out with vise grips. Most come out easy, if its stubborn warm the area with a propane torch (carefully). I have an idea. Have you removed the primary cover yet? If the PV linkage came loose, either the setscrew on the belcrank, lower end of the rod, or the entire mechanism from the case, the PV would just float and be under no force, that would explain the change in tone. It would also explain the rattle on restart. Now, if something is loose in there, it could have caused a lockup. Just a thought, not a normal issue by any means, but worth checking out. This is an interesting one. |
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