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Electra only firing on one side


I'm only getting my Electra to run on one cylinder.  It starts immediately with both plugs connected  using the starter, but only the left side gets hot.  Will also start with left side only hooked up.  Won't start on right side only.

new coils

new plugs and wires

new v reg and rectifier

new Pazon e. ignition

good spark both sides

new Amal carb

valve setting double checked

compression = 160 both sides (cold)

Anyone have an idea?


Why would one size fire and not the other if they both had the same caps?


Check to see if all the valves are opening. On an engine I rebuilt a few years back (Not a light twin though) one of the pushrods slipped out of the rocker whilst I was juggling everything back into place. Took a while to find it. If your right inlet valve is not opening, then no juice gets in so it won't fire.


Hi Jack, the way the Paxon system works both plugs spark at every revolution of the engine using both coils so if one side is firing then provided all is well with the HT lead, plug cap and plug on the other side it isn't going to be an ignition problem.   Therefore I would start by checking the right hand ignition lead, plug cap and plug by swapping the components over and see if it now starts and runs on the right hand cylinder and transfers the problem to the left side.   I have had leads, caps and brand new plugs spark happily when not under load but break down under compression - a classic was a hair line crack in a brand new spark plug's ceramic insulation which baffled me for several days!    It showed a fantastic spark held against the head to check it but when it was screwed into the head the current was tracking to earth down the crack and cutting that cylinder completely.   As Robert points out plug caps can suffer from similar problems too as can leads.   If the compression is that good then as Duncan suggests I would remove the rocker covers and check that both push rods are seated properly and the valves are opening and closing - I have had the pinch bolts loosen off so much the push rod has jumped out of the inlet rocker before now cutting that cylinder completely.    With a single carb it is difficult to see how it could be a fuel system issue - checking the right hand plug after you have run the engine briefly to see if it is wet with petrol might help your diagnosis!    Good luck and keep us posted.



Right hand plug is wet.  I'll try swapping the HT leads today and pop another plug in the cylinder.  Will also take a close look at the rockers if that doesn't work.    (Pulling and replacing the valve covers is such a hassle on the Electra.  And I just sealed them up nice and tight after resetting the valves.) Thanks for the ideas.


Sounds like you are pinning this down Jack, the symptoms are pointing towards HT leads, plug caps and plug!   Having never been lucky enough to own one I had forgotten about the Electra rocker box cover clearance issue - lets hope it is an ignition system problem!   Looking forward to hearing what it turns out to be! 


I had this earlier this year, Nicholas Clarke nailed it. I’d checked the spark on both plugs, but only one was working in the engine. Swop them over and see if the hot side changes!



I hade the same problem last month with my Guzzi. It turned out to be a faulty NEW coil.

That was the last thing I expected so it took a while to track down.

Swapping the coils over identified the problem but not before I tried plugs, points (not in your case, HT lead and cap and even the carb!

Note that the faulty new coil gave a fat spark with the plug out of the head but for some reason did not do its job with the plug in - I don't know why. 

Swapping the coil, HT lead and cap as one eliminated the possibility that the HT lead or cap were faulty and I reused the cap and HT lead with the problem solved so I know they are good. 

Like you, one cylinder got hot and the other did not. This heating swapped sides when the coils were changed over. I too use the Pazon system and it works well.



Like you a did, Dennis, I did a bit of swapping around of plugs, HT leads, caps, etc. this morning without success until I got to the coils.  Then VIOLA.  Bad coil - which was brand new.  I put the old coil on the right side and everything runs great.  I rode it around the neighborhood a bit and it has great acceleration.  I couldn't get it out for a high speed run 'cause it is not yet registered (I wanted to wait 'til it was actually running.)

Now i need to give the gearbox a once-over.  I'm not getting all the gears the way I should and the clutch is quite hard to pull.

Thanks once again forum members.  I really appreciate having this site as a source.


With the twin cylinder electronic ignition we have a wasted spark system ie both coils fire at once timing is the same so you can swap (has an a in it!) the HT leads. BUT there is a fault where you get a spark on one cylinder/coil only-so you swap coils or replace the dead coil. But you still might have a problem. The problem is that the working coil has an earth fault that allows it to work but stops the other coil (which is a good coil) from working. Any doubt with all this replace BOTH coils, this is alo a good idea if the original coils are quite old.

Finally I see you got the Electra sorted, duff new coil! that means you used ones out of a Lucas Box or even PVL. So the HT comes out from the end, a nuisance on the Electra as the original Wipac coils come out the side and hang down under the tank. So when I went to Electronic ignition years ago I got hold of some old 6V Wipac coils-to replace the original 12V ones and they are still going strong.


To add to A O's examples I was hit with the single spark on a wasted spark system and all of the components were good and even when replaced with other known good items the single spark persisted. Only after I added an addition earth wire from head to battery terminal did the bike return to 2 sparks, seems the old earth wire in the harness had degraded and only allowed enough current to pass to support one spark. Going back to points would have worked too until the earth wire completely failed as points is sequential spark not wasted. 


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