'78 R100RS Only 1/2 the Engine Firing

[bmr bill]

Good Day All. After being idle for 5 years, and rebuilding the rear disc brake system (frustrating, but not difficult) I have the bike running again.
The problem is the LEFT cylinder runs fine, but the RIGHT side is not firing.
The Facts; Dual plugged with a Boyer Branston ignition system. Del- Orto PHM 38 Carbs. (bought bike this way) With the bike sitting so long I tore the carbs down to ensure all jets and passages were clean. Checked float height (18 mm). Found the left accelerator pump was not pumping at all, reset to 0.4 ml per full throttle twist. Valve clearances good (0.15mm in. 0.20mm ex.)
Right side facts; compression 120 pounds, Spark-YES, Fuel-YES
Swapped left and right plug wires to make sure both coils were working and the left side still fired and ran the engine. Using my hand and an infra red thermometer Left side head gets hot quickly Right side barely gets hot. Pulling plugs after running a couple of minutes, right plug is warm, left is HOT. My feeling is right side heat is coming from hot exhaust from left side.
Looking at PLUG photos, the right might be igniting intermittently.
Any thoughts or direction are greatly appreciated,
Bill

 

[20774]

So how are the coils wired to the cylinders? Typically one coil fires the top plugs and the other coil fires the bottom plugs.

Have you tried swapping plugs?

 

[bmr bill]

Left coil is top plug right, left plug lower. I will try switching it around. I did put my timing light on left side upper plug wire and light appeared to flash/strobe normally but the timing marks were erratic as strobe flashed. Hooked light on right wire and strobe light was noticeably erratic.This makes me think that there is an issue within the ignition system. Hopefully not in the little black box. I will be swapping out coils with spares that I have, as well as wires, if I have some.
Cheers

 

[bmr bill]

It looks like a faulty coil and a damaged plug wire. Hopefully have it dialled in tomorrow .