520 SX -02 crank stops at TDC, WTF?

[Anssi]

I have the clutch removed (disengaging the transmission and kickstarter from the process) and have the valve train cover and stator cover open (everything seems ok with the cam, auto compression and other stuff inside those).

I can rotate the crank by hand from either the crank end on the clutch side or the stator between about the TDC before the exhaust stroke and the TDC after the exhaust stroke.

At both ends of that, the crank just stops dead as if I had the stopper bolt (that is used in the valve adjustment procedure) screwed in. However, I have that bolt as well as the spark plug (in good shape) completely removed.

I'm going to remove the flywheel/stator/whatever the thing is at the end of the crank and see if a better look at the cam chain will provide more ideas before the cases come apart.

Any ideas about what might be wrong?

What happened before this problem:
I get to the track and let the bike idle for about a minute. I adjust the idle a bit higher. After I ride about 10 minutes I notice the idle has crept up. Thinking this is because of the bike getting warmed up, I get to the pits and pull in the clutch. The revs rise to what would normally be about 1/4 throttle at neutral (pretty high revs). I hit the kill switch, adjust the idle and try and start the bike. The kickstart lever stops when I try to kick the bike over, probably at TDC. I take the bike home and start working on it, not yet finding the problem.

I have never had the engine this far open, but I do understand how it works.

Thanks in advance for any possible help.

 

[jsned]

Anssi, I aint even gonna pretend I know what it could be. But I wonder if something has come loose and fell in the cylinder somewhere at a port and is not letting the piston by?

Did you post on KTMtalk.com? If not give it a try I have had better luck for something like this on KTMtalk.com

Hey if you figure it out let us know. Good luck!

 

[Anssi]

The plate that is on the throttle slide had had a part break off and enter the cylinder, jamming itself between the piston and the head. No additional damage to be seen (the super-high idle when I stopped was probably due to the slide effectively missing a part). The little plate will cost me 140 euros. Nice.

I'm getting rid of the tractor and will get me a YZ, CR or RM 250 2-stroke, the crap-building Austrians can keep their sorry excuses for race bikes (the bike has 105 hours on it, I maintain it religiously, and I've had a cam bearing failure, valve rocker failure and a transmission bolt come loose).

 

[TexKDX]

OK, so the Keihin FCR suffered a failure. Guess what, the Suzy and Yammie 4 strokes have the SAME CARB on them.

So much for slamming the Austrian bike on this failure.