Points cam not spinning. But valves move

drummerking55

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Hello everyone I have been on this forum for a while. I had a 1981 special a few years ago but ended up selling it. Now I have a 1979 xs650 special that I am trying to get running but I am having issues. First off finally got her to fire up by reversing the spark plug wires. She ran for about 10 seconds then died. After that no spark. So I took off the points cover and the cam is not spinning. But the valves moving. I took off the timing advance side and the rear gears are spinning but the advance is not. Did a pin fall out or something. Don't see one at all. The the previous owner I know did some odd stuff to it so maybe it was forgotten on reassembly. Any help would be greatly appreciated. I am going to try and include a pic of the bike as it sits now.
 
image.jpeg
 
Did a little more tinkering. Here is somthing wierd, I turned the timing advanced side clockwise about 3 turns and it tightened up. Now it's all turning together but I'm guessing my timing is now way off. It does look like the pins are installed in the key ways
 
What keeps the advance plate in place on the cam is a pin on the back side, that cogged nut keeps it tight. I would take it off to check the pin and slot in the plate for wear and tear.
advance pins.jpg
 
Ok it looks like there are teeth on the inner plate that let you hit it until it's tight. If I inspect it and all looks good should I just put it back on and tap it till its tight?. Will this all effect the timing? I think it must because the points side was free spinning
 
You need to see if the pins are in there.
Yes, the nut holds the advance plate on, however, if the points cam is spinning then it still won't work. Your timing will be off. The cam needs to open and close the points at a certain time.
 
When the cogged nut loosens, the slot in the ATU rotor slams back and forth on the pin. Usually it either distorts the sleeve or breaks a chunk out of it. Check compression: that loose nut can result in a holed piston. You wouldn't have caused the damage because the motor died on you too quickly, but you don't know what the PO might have done. BTW the tip of the weight shown in your photo is severely worn, and you won't be able to set timing correctly at both ends of the advance curve with the weights in that shape. We've posted plenty about that condition and how to correct it, seek and you will find.
 
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Often when the nut is loose, the slot where in the advancer that rides on the pin gets hammered open very wide. This extra slop allows the advancer to slop around and your timing will not be right. If the slot is ok, put it back together. If the slot is excessively worn it needs to be replaced
Once assembled you will need to check the timing. Your repair manual has the procedure for setting the points gap and timing.
Set the can chain tension first. This removes any timing variations from excess play of the cam chain.
Leo
 
Thank you for the advice. As suggested I took apart the timing advance set up. It was missing the inner pin that keeps the cam shaft and the timing rod in sync. I measured the proper size and length pin and made one up. Reassembled the whole thing and it started right up. The advance fingers and center wheel do look worn so I am going look into replacing them. Thank you all again for the help.
 
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