Coil finally giving up.

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1971 with a older Boyer ignition and some mystery coils with 17M6 is stamped on their bottoms and they look like they've been on the bike a long time. Left cyl. keeps cutting out (no spark) while having a good run, once the bike gets hot. I pull over and check and there's no spark, I let the bike cool down for a while and she has spark. Time to bite the bullet and get some coils I guess......... any recommendations??
 
If your plug is not sparking... you won’t have a spark...!

Could be a duff plug is all I‘m saying.

I‘d buy trying new $2 plugs before new $?? coils if it were me...
 
1971 with a older Boyer ignition and some mystery coils with 17M6 is stamped on their bottoms and they look like they've been on the bike a long time. Left cyl. keeps cutting out (no spark) while having a good run, once the bike gets hot. I pull over and check and there's no spark, I let the bike cool down for a while and she has spark. Time to bite the bullet and get some coils I guess......... any recommendations??
The mystery coils are Lucas and probably original to the bike. Is the coil hotter than the other one - they should not be hot. If not, I would swap the spark plugs and see if the problem moves. If not, I would swap the spark plug wires and see if the problem moves.
 
The clamps that hold the coils are often overtightened and crush inwards the coil bodys. Check for that. Snug fit only.
 
No... it’s to get someone else to do that and see if they Yelp !!
Long story - there is a point...

I've been working off and on with a guy with little mechanical aptitude and even less electrical aptitude. It's a 79 Bonneville he bought new. I fix it, test it, have him test it, and then in 1-2 weeks he's messed with it and it won't run properly. The last time I rebuilt the MKII carbs, put in the correct spark plugs, and admonished him severely for letting the bike idle on the side stand with the enricher on, for 10 minutes! He took the bike home, rode it a couple of times and then called me saying the left cylinder wasn't running. Of course he assumed I screwed up the carbs. I tried to get him to check the spark but he assured me that since he had Tri-Spark and a dual output coil that it was not possible to have spark on one cylinder and not the other. I finally got him to pull the plugs, reconnect them to the plug wires on and put the plugs on the head and then kick. Now he told me he couldn't see spark in either plug. By now I was quite frustrated and gave him three options:

1) Call someone else to work on his bike (good luck on that).
2) Get his wife to look at the plugs with something to shield the sun while he kicked.
3) And, here's the point of this story: I told him: "Man up, grab the plug with your hand on the business end and the same hand touching the head, and kick". He said, won't that shock me"? I said, if there's spark it will but it won kill you.

At that point, he started listening, and magically could see the spark on the right side and none on the left. Had him swap the plugs - problem didn't move. The wire were molded into the coil so couldn't swap them. Had him unscrew and swap the NGK caps - problem didn't move. Told him to replace the coil and call me. Bike is running great again - I wonder how long this time.
 
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Well I did it to a mate when I was 16. Got him to hold the plug whilst I kicked over my SS50 to “see if it was sparking”.

I was barely able to contain my laughter as I kicked it, but no Yelp, so I kicked harder, and again, and again.

”Isn’t it sparking” I asked.

“Yes“ says he.

He was watching it sparking in his hand !

He did it a couple more times with me watching (in amazement) and then he YELPED... we were in my cramped shed and he’d touch something metal with his arse and earthed through his arse !
 
Welp, I've done my share of piss'n on an electric fence on a dare as a kid and as an "adult" I've been tossed off the fender of my old truck while grabbing cracked/rotten plug wires far too many times..... I'm sure there's some brain damage involved.
Back to the story at hand tho.................
Found the issue. Piss poor ignition switch cutting out on me, only getting 6-8v to the ignition through the switch and if jiggled the key power would be very erratic at best. Pulled the switch and hooked a jumper between 1 and 2/3. Lights were finally bright, and bike fired on first kick and sat there rumbling not missing a beat. Ran it up to the redline and finally no cutting out/popping. Guess low voltage was reeking hell on ignition and the left coil just said "screw you, I ain't going to fire".
Now the quest for a pre 72 quality ignition switch. Any better than others????
Thanks,
M
 
Welp, I've done my share of piss'n on an electric fence on a dare as a kid and as an "adult" I've been tossed off the fender of my old truck while grabbing cracked/rotten plug wires far too many times..... I'm sure there's some brain damage involved.
Back to the story at hand tho.................
Found the issue. Piss poor ignition switch cutting out on me, only getting 6-8v to the ignition through the switch and if jiggled the key power would be very erratic at best. Pulled the switch and hooked a jumper between 1 and 2/3. Lights were finally bright, and bike fired on first kick and sat there rumbling not missing a beat. Ran it up to the redline and finally no cutting out/popping. Guess low voltage was reeking hell on ignition and the left coil just said "screw you, I ain't going to fire".
Now the quest for a pre 72 quality ignition switch. Any better than others????
Thanks,
M
We have 14 acres and (now) five horses. They always mess with the floats on the watering trough, so they either dont fill or dont turn off;. Had a wont turn off event, and told the wife to turn the fence off as the trough sits half on either side of a hot 5 wire fence. Had both arms in up to my elbows and the top of my head hit the wire. She had forgotten to turn the fence off. The shock sent me back a couple meters onto my ass. Had a headache for a couple days. Was not pleased.
 
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