I recently borrowed the 6v coils on my Mk3 to test on another bike. Now I've put them back on the Commando I have developed a serious backfire on one cylinder.
I have triple checked the wiring, swapped the coils & HT leads between cylinders, replaced the plugs and checked the timing. It starts OK but develops the back fire within a few seconds. It was running fine previously. I'm running a Pazon ignition and a single Mikuni carb.
Any ideas what else I can check? Thanks
Backfiring is typical of an…
Backfiring is typical of an intermittent ignition fault ..
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Thanks for the responses.
You were right, the problem was ignition. But it turned out to be another dodgy plug!
Having swapped coils again, changed leads etc. I was running out of ideas. As a last resort, I put in a further set of new NGK plugs and all miraculously worked!
Why 2 separate Champion plugs failed is a mystery?! But I'll stick to NGK in future. Thanks
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I've read there's been some…
I've read there's been some fake plugs on the market in the recent past, NGK and Champion.
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If this 'backfire' is on one cylinder then it can only be a problem with one of the coils and it can be the coil that is on the working cylinder that is faulty! (I know this) another clue is that it might start ok and tickover ok but any revs causes the missfire. IF so then one of the coils might be breaking down to earth with the higher voltage, cause might be over tightening of the clamp. In which case I recommend two new coils-do not replace one coil, keep the good coil as a spare for another day/fault.