Hi all, I am replacing all my ignition system. New plugs, leads, caps etc ordered but I am struggling a bit in trying to choose coils so am looking for advice please. The modern 1&7/8" Lucas 6v coils (made in India) get a bit of bad press around reliability. Whilst I want to retain originality, I am not too precious when it comes to sensible upgrades. E.G. the bike has a Boyer electronic ignition. I want to replace my coils with reliable and ideally higher powered (to allow a bigger gap / spark) coils of the same size and connections. Any recommendations on coils available in the UK please? Thanks Ian
What bike and is it running a 6v charging system or is it a triple? Boyer states that coils should be between 3 and 7 ohm resistance so any coil that fits that criteria should be OK whether it be single or twin output.
Thanks for the fast reply. It is a 79 T140e Bonneville. It has the original 2x 6v coils (wired in series). Problem I have is identifying reliable high-quality new coils to replace the old ones. Any recommendations please?
That would have been right for the original RITA ignition amplifier but if you have now fitted a Boyer Branson unit the 6v coils will likely be the wrong resistance for it so this may be the problem, coils are much the same when output is concerned and the primary resistance will play a part if too low it can damage the amplifier and reduce spark output.
Interesting, thanks. I didn't know that. Both of my coils LT side measure 1.9ohms, so that is 3.8ohms total.
So, I checked the HT circuit. There were resistor caps and resistor plugs, doubling resistance to 8.5k ohms, and the HT leads were also quite tired. So I replaced with new high'quality cables, non-resistor plug caps, new coil caps and new non-resistor plugs, then retested. Better regularity of spark but still not great distance jumping (only the lowest 1mm gap on my tester at atmospheric pressure). So I bought a pair of high-power Trispark coils and fitted them. Now the spark is jumping 5mm easy so, after some rough calculations, I opened the plug gaps to 0.35 for a bigger spark and refitted everything. Bingo! Whilst she is still a little challenging to start cold (I am told this is not unusual but I may experiment with the enrichment jet sizing in future), she now starts warm very easily and 1st time, every time! I only have to tickle the kickstart now
Yes a lot of the earlier electronic ignition systems like the RITA do not like resistance in the HT side...not sure about the Boyer though, later ignitions are made to have higher HT resistance to avoid radio signal interference etc.
I've always used Lucas coils, i have seen a few company' s sell them. Got mine from https://www.classicbikeshop.co.uk/6-volt-coil.html
