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By Hugh
#4731
Hope someone in the RE community can kindly help as getting desperate after some 6 months of off and on attempts to solve a problem. Have Boyer electronic ignition fitted on my 1971 Triumph Bonneville T120R Oil in Frame. Bike runs fine on one cylinder on starting but other side is running unevenly. If I try to start/run on a single cylinder by disconnecting one HT lead it will start and run on the good cylinder but nothing happens on the bad side as when just connect this side up - no starting and no running. Change coil leads to test on the alternative cylinders swops problem to the other side when both cylinders HT lead connected so good cylinder becomes bad and bad cylinder is now good. Similarly single cylinder starting/running issue are reversed. Have 2 6 volt coils connected in series as advised by Boyer.

Bike was originally when bought in 2004 (and not knowing the Boyer advice) run by me on 2 12 volt original Lucas coils in series for 10 years with absolutely no problems in terms of running and starting at any time till recently. Towards the end of this period it was however starting to play up a little in terms of uneven running/hunting. This was when on investigating I discovered the coils were not as Boyer advised so changed to 6 volt coils in series expecting to solve issue (overly optimistic here then!). If, however, now I try putting the new 2 6 volt coils to work in parallel (against Boyer's advice) everything seems to work as it should and seems/sounds back to normal in that starts first time (as always done) and runs evenly. I have tested both 12v and 6v coils (and the battery is OK) with both primary and secondary circuit readings within tolerances. Any advice would be appreciated as even thought of returning Triumph to simplicity of points as my 57 350cc Bullet with Lucas magnito has been a peach in terms of its starting and running ability over my custodianship (owned/rebuilt 2007). Thanks very much as slowly tearing hair out (what little have left). Regards and good and safe riding to all for the new season coming up. Hugh
By Norm
#45109
Personally I would run it the way it runs best and forget the Boyer instructions, what have you got to loose, it it fails just go back to points as you are contemplating
By John L
#45116
Hugh - And before you try that - have you tested compressions ? with a gauge ? (If you don't have 2 GOOD, EVEN compression readings to start with, all your other efforts to get it to run right will be a total waste of time). Good luck with sorting it.
By Tim NZ
#45118
First off, running any motor with a plug lead disconnected and NOT earthed is bad for the coil; it will end up frying it.
Doing so with EI and it happens sooner. The insulation of the HT windings burns through.


12v coils are OK with the Boyer, 6v is preferred but will still run ok for road use.


Both plugs fire at the same time, so your issue is with the coil/lead/cap/wiring connection to/from that one coil. Make certain that you don not have broken wires inside the insulation at the terminal connection...


If the wiring is original it is highly likely that you will have cracked insulation and or copper strands.


Check that the inside of the coil output towers are not oxidised/corroded where the plug lead seats.

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