520sx motor problems

has anyone heard of this, I was at the track and about to kick start my bike but it seemed like the motor was locked up, the de-compression would not free it up so I put it in gear and rocked it backwards and then I was able to start it up. After a couple of laps it started making a bad knocking clackity sound. I shut it down and went home and fired it again and it made the same noise, I revved it up and it clanked hard and stalled the motor. I pulled the top cover and the valves are ok. It will turn over now but sometimes locks up and I have to reverse the motor to get it spinning again. I have the motor out of the bike but not sure what to do next?

Sounds as if your going to split the cases to find out.

Your certain the valves are adjusted properly? The symptoms you mention sound very similar to my recent valve adjustment mishaps. I didn't have the motor at TDC when adjusting the valves. I was unable to start the bike unless I jiggled the motor a bit while in gear.

Where is the sound coming from? Cracking the case would really suck. Good luck!

do not run the bike until you check this....... take the rocker cover off the bike (can be done in the frame) rotate the camshaft to TDC compression (cam lobes facing down) now, right about 11-o-clock on the cam sprocket there should be a small allen head bolt and nut that go through the sprocket (it is the decompression stopper for the centrif' weight) item number 28 and number 50 on page 11 of the 02' engine book. i have heard of this bolt loosening up and falling into the engine causing the symptoms that you have described. if this is your problem, take off the stator cover and search for the parts before running it again (replace the bolt and nut of course)

Thanks a million dstktmusa, I had already pulled the motor and taken it to ktm shop to split the cases, they hadn't started yet so I had them check this over the phone and sure enough the bolt is missing. I'll let you know when we find it.

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