Engine cutting out

1975 MK111, just had the bike re-wired. This is what it has on it AMALpremier carbs, good spark plugs, the wire from the pick up plate on the BOYER is good. Micro DIGITAL BOYER I put on in 1993, the bike had 11,500 miles on it then now it has about 82,000 miles on it, I have gone through a few. Speedo drives.. good battery .. The bite starts right up sounds good runs good but the ignition cuts out. There was still power going through the bike. The ignition light is on, it will restart after a while.The guy that wired, the bike
moved the BOYER box up between the coils, it sits inside a stainless steel box that I had made. The box was on the down tubes now it’s up above the engine, BETWEEN THE COILS
Is the engine cut out possibly caused by overheating and old age in the ignition box? The bike has been very reliable to this point. I have a new micro power ignition, that I can put in if no one has a better idea.

Thanks, UR

Check the primary and secondary resistances of the coils, the coils also can overheat and stop sparking. Also check the coil case as the clamps distort the cases and create internal shorts.

kommando said:

Check the primary and secondary resistances of the coils, the coils also can overheat and stop sparking. Also check the coil case as the clamps distort the cases and create internal shorts.

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Will do,
Tks

Is the choke fully opened?

MichaelB said:

Is the choke fully opened?

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Yes, the choke is Ok. it feels like it is the box or the wire on the pick up plate.

I had a twin coil where it was specified as 3 ohms, just on the bottom edge of the Boyer spec but it measured 2.9 ohm. The symptoms were on hot days the Boyer lasted 20 mins before stopping producing a spark, turn off ignition for 15 mins then got you another 20 mins of running. Cure was a coil with 3.4 ohms resistance. On another bike still on points the coil itself overheated after 30 mins, sparks stopped, ignition off and then another 2 miles, ignition off 10 mins then 2 miles etc etc until I got home. Coil was hot to touch and a new coil was the cure.

Some of these suggestions I have had and some are guesses based on your claim that your problem is electrical in nature
1) worn key switch contacts- happens faster if you have the weight of a fob on your ignition key.
2) Intermittently working spark plug- it heats up, has an internal crack in the porcelain and sparks up inside the plug body instead of at the tip. tests good cold, but cuts out when hot.
3) Corroded/ sticky kill switch.
4) Poor terminal connection somewhere- The hide and go seek game of motorcycling. I would open the headlight shell to see if any of the mess of wires in there have frayed and are grounding out intermittently.
5) Poor charging system/ bad cell in the battery/ old battery- If you use a battery tender, (like I do) it can top off your battery, then the battery voltage drops as you ride until you get the ignition cut out. If you let the bike sit, you get back a little surface charge as the voltage levels out and everything works again for a while. The battery tender makes the problem hibernate by raising the voltage in between rides, so you can't find the problem.
6) Crushed coil/ bad coil/ pick up wire crack- All the known ignition problems
7) Poorly grounded- It's best to add some extra ground wires to a rubber mounted engine.
8) Skinned/ worn through wire rubbing the frame- could even be a directional wire.
9) Rotor rubbing stator- heats up, shorts out. The stator will show signs of overheating rainbow colored stator plates from overheating...

Those OEM coil clamps have an unbelievably low torque spec - it's below 1 ft lb.
A friend of mine destroyed (crushed) several coils before he woke up to what was happening.