No spark on one side

warrenlevihursh

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Background: I am not good with electrical stuff. Its a 1978 with points and original coils. Bought the bike with the advance rod, points, weights etc in a box. Not running do to being an unfinished project. I finally got all the small missing pieces and attempted to assemble everything last night. I am pretty sure everything is correct, I've read a fair amount here on the forum.

My question is, could the spark problem be due to the points being incorrect? I assume the brushes on the rotor couldn't be the problem because my spark issue is only on one cylinder? I am leaning to a coil problem because the spark switched sides when I switched the coil wires. I am going to Ohms test the coils when I have time.

Any help is appreciated. Thanks.
 
Yup charging system is completely separate if you are working from a fully charged battery.

Yes ohm out the coils, set points, test condensers. Consider a new points, condenser set, points wear out, condensers die of old age. check plug wires and caps (swap)
As always check all wires, connectors, grounds.
 
Yes, it could be a points problem. Maybe only one set is functioning correctly. Or maybe there's a break in the wire leading from one points set to the coil. You said you switched wires at the coils and the spark changed sides. I'm assuming you switched the wires that come up from the points. That would seem to indicate either a problem in one of the wires or with the points set it connects to. One points set and it's wire will fire either coil, the other won't fire at all.
 
Yes, it could be a points problem. Maybe only one set is functioning correctly. Or maybe there's a break in the wire leading from one points set to the coil. You said you switched wires at the coils and the spark changed sides. I'm assuming you switched the wires that come up from the points. That would seem to indicate either a problem in one of the wires or with the points set it connects to. One points set and it's wire will fire either coil, the other won't fire at all.

Yes I switched the wires from the points, I didn't even think the coil must be good if it fires with the other point set. I was thinking I switched coils, but I don't think that's what I did. Thanks!
 
Yup charging system is completely separate if you are working from a fully charged battery.

Yes ohm out the coils, set points, test condensers. Consider a new points, condenser set, points wear out, condensers die of old age. check plug wires and caps (swap)
As always check all wires, connectors, grounds.

Thanks for the reply. Plug wire, caps and plugs are new and I made sure the are making a good connection at the coil.

Ill research about the condenser. I eventually am going to switch to the PAMCO I have, but I wanted to get the bike running first before I spent a bunch of money on the Dual output coil and electronic advance.
 
Ok i got spark on both sides! Nice and blue. The orange wire on the points was messed up a bit. Now its good so the right cylinder fires. The bike just back fires thought when trying to start it. Could my timing be off? I dont want to keep trying it. All the pins are lined up, i dont know how it could be wrong?

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The top set of points should power the right cylinder/coil, if the advance rod is correct. You should see an "R" stamped into the points backing plate near that top set. That's what it means. Usually, the gray wire goes to that set, orange to the bottom (left) cylinder points set.
 
I switched the points wires and it fired. I shut it off because it didnt sound great. It was smoking pretty good and the oil filter cover was leaking bad. I need to charge the battery and ill try it again.

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I gotta jump in here and say; THAT was a fun read! I love it when somebody posts a problem on here and you guys literally talk him right to the source of the problem! That is friggin' AWESOME!!!

*Also; you guys just answered several of MY ignition questions wham-bam! THANKS!
 
Last edited:
1 issue resolved, 40 to go. And that's how it goes reviving an old neglected motorcycle.
 
Yes, these old 650s need lots of love - lube love, wrench love, you will be hugging it often at least for the first few seasons, lol. Once sorted and fixed up, I think this is a wonderful bike, the perfect local ride. Big and heavy enough to ride nice, but small enough for easy around town and parking lot maneuvering. Also, it's got enough power to be fun. It's a real, honest, old fashioned motorcycle.
 
Thanks guys. A few quick questions. It was kicking back a bunch so i adjusted the cam chain, adjusted the valve lash and redid the points. Now it is just backfiring through the carbs. How much does a low battery matter with points?

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That SOUNDS like ignition timing to me... The kicking back- I think -means you're igniting your mixture early (sparkplugs firing early and blowing back thru the intake and thru the carbs because the intake valve isn't closed yet during the compression cycle). Since you've been tinkering with your ignition, it may just mean you have to re-time or play with your timing on it.
 
Yes, the timing being off, even a little, can cause kick back. These dual points systems are a PITA. You're basically setting two separate little ignitions, one for each cylinder. And then for best running, you should try to match the settings between the cylinders, both the points gaps and the timing. It can be a real chore.

Yes, a low battery matters with points too. The low speed misfiring is one of the signs of that. If the battery gets too low, it won't run at all. Both the stock ignition systems (points and electronic) need a good and near full charged battery to work correctly.
 
you redid the points..... Did you read the whole thread?

For both posters; as always remove clean and lube the advance rod. Check for free action of the rod and check the advance springs.
 
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