Hey guys. I got a 2000 scrambler 500 from a guy in a garage sale. Needed stator and some drive terrain maintenance. Installed new stator, got good spark back. Then i discovered the timing was off about 180° . Realigned timing marks in cam and it fired right up and ran excellent for a few minutes then i shut i down. When i went to restart a few days later it was backfiring again. Checked tominv marks and they were off about 20°. Wasnt sure if it was my mistake so i realigned marks again. Fired right up ran excellent . Few days later ... same thing happened. I can hold the cam gear and pull the recoil, engine turns over and timing gear dont move. This must mean the key way on the crankshaft is sheared. So my question is how dificult is the repair and is it worth it? Do i have to split the crankcase? Im really bummed. Put a lot of new bearings bushings axles and electrical work into it thinking after i first heard it run it was worth it but now im unsure. Just ordered a repair manual. Just looking for opinions or ideas. Thanks in advance.

 

Had this happen more than once! Just pull the flywheel and the stator plate and you'll see the cam drive sprocket and the slotted nut. If it's like a lot of ones I've torn into, the nut will back off and actually make a groove in the back of the stator plate. Usually before it backs up too far the flywheel key will usually shear off allowing the sprocket to turn or distort enough to cause the cam chain to jump teeth,altering timing. The slotted nut has REVERSE threads! Left to tighten ,right to loosen. You don't have to have the slotted socket as a good punch and red locktite will suffice. Usually you need to replace the sprocket,woodruff key and cam chain while you're at it,plus you need to remove the tensioner. The small sprocket has a dot that lines up at the mark at the bottom of the case(TDC) the new chain goes on up through the cylinder head with the cam sprocket index pin at the center of the head. Even though this pdf manual available is for a 2009,the engines are the same. Has a good cut away picture on cam chain timing and how to repair it. PartShark.com - Motorcycle Parts, ATV Parts, UTV Parts, PWC Parts, Powersports Apparel, Motorcycle Accessories for OEM and Aftermarket.

 

Thanks a million. You and many other guys on this site have been so helpful. I have a 96 500 with a bunch of things wrong. Been slowly exchanging parts onto the 2000. The motors look the same besides the size of intake and exhaust diameter. Could i use the bottom gear and chain from that motor?

 

You can,BUT just my If I'm down there it's getting new parts period!! Guess I was a mechanic too long!!

 

Ok so i was able to get to the lower timing gear and found broke in half. My next problem is that the woodruff key for the gear is nowhere to be seen. I fear that it is in the base of the motor. Not sure what to do besides try fishing around with a magnet. Any ideas would be appreciated.

 

Small flexible magnet is the best to see if you can find it or parts of it. Could have sheared into several small pieces.