COILS . Well , suit yourselves then .

Matt Spencer · Feb 14, 2022

acotrel · Feb 15, 2022

I use a 12 volt double-ended coil off a Honda 4 with my Boyer. It never misses a beat. But I am only on 9 to one comp. ratio.

Onder · Feb 15, 2022

Wow, I was just thinking of that article the other day....K-Mart Coil the winner. Amazing what old people can remember...

SteveA · Feb 15, 2022

When I originally built my Rickman in '75/'76 with an 850 race motor I could not get it to start...

I had a nice blue spark, but nothing happened except the odd fart...and of course this was push starting....it wasn't that easy to get it to turn over....

Eventually I too it to a friend at a traditional bike shop...

He suggested we test the coils on the Sun tester, I told him they were new 6v Lucas items, complete with ballast resistor.....no we will test them he says.....sure they spark until you pull the gap a fraction.

So we put on a pair of el cheapo 12V CZ coils....starts first push.....

Matt Spencer · Feb 20, 2022

triumph2 · Feb 21, 2022

Onder said:
Wow, I was just thinking of that article the other day....K-Mart Coil the winner. Amazing what old people can remember...

I remember the term "God's own lightning" being used to describe the K-Mart coil.

Tornado · Feb 21, 2022

Later model carb'd cars and early FI cars used single 12v coils and resistor plugs,resistor leads and resistor caps (typically around 10k Ohm total). Why is the most common recommendation for our bikes is to use no more than 5k Ohm (ie just resistor plug or cap, not both)? Is this b'c of the two 6v coils being unable to give adequate spark at higher resistances?

Any potential issues with the EI's we are typically using if running 10k Ohm and modern 12v coils?

marshg246 · Feb 21, 2022

I'm rusty but if I remember right the resistance has only a little to do with the high voltage but greatly reduces the noisy lower voltage spikes caused by the coils secondary collapsing to make the high voltage and the spark jumping the gap.

I did this "seat of the pants" experiment and found no difference in running. Tri-Spark ignition:
1. Non-resistor caps and non-resistor plugs *
2. Resistor caps, non-resistor plugs.
3. Non-resistor caps and resistor plugs.
4. Resistor caps and resistor plugs (makes 10k Ohm)

* My LED oil pressure warning light continually flickered with engine speed so it appeared that I had no oil pressure at higher RPMs. That noise can upset the Tri-Spark as well but rarely seems to. I you have accessories on the bike they can be upset by the noise.

Tornado · Feb 21, 2022

marshg246 said:
I'm rusty but if I remember right the resistance has only a little to do with the high voltage but greatly reduces the noisy lower voltage spikes caused by the coils secondary collapsing to make the high voltage and the spark jumping the gap.

I did this "seat of the pants" experiment and found no difference in running. Tri-Spark ignition:
1. Non-resistor caps and non-resistor plugs *
2. Resistor caps, non-resistor plugs.
3. Non-resistor caps and resistor plugs.
4. Resistor caps and resistor plugs (makes 10k Ohm)

* My LED oil pressure warning light continually flickered with engine speed so it appeared that I had no oil pressure at higher RPMs. That noise can upset the Tri-Spark as well but rarely seems to. I you have accessories on the bike they can be upset by the noise.

That is how I understand it, but thought i'd read a few yrs back that too much resistance can cause a feedback voltage into the coil or was it the EI supply low tension leads into coil? Hence advice not to crank engine without both HT leads having path to ground (via spark gap or shorted direct to head).

Triton Thrasher · Feb 22, 2022

Tornado said:
That is how I understand it, but thought i'd read a few yrs back that too much resistance can cause a feedback voltage into the coil or was it the EI supply low tension leads into coil? Hence advice not to crank engine without both HT leads having path to ground (via spark gap or shorted direct to head).

In marshg246’s case, it appears that 10 kOhm wasn’t too much.

Coolhands · Apr 23, 2022

I’m having the weirdest week.

Ended up going with trispark coils. Got everything sorted replaced all the connectors and got rid of all the POs weird splices. Found I had a dead spark plug too!

Starts good now. Thanks everyone.