Yes, I was thinking electrical although I am in the process of checking the carbs. It cuts out then back too quickly to be fuel related. I was hoping there was a group here who had similar issues and pinpointed it to one component. Something like a weak link in the electrical system. I'll look at the ignition switch as see if cleaning it does the trick. My only concern is that it may seem to be fixed, I take a big trip and pop! I'm stuck on the side of the road.

Thanks for the help.

Eric

Oh man, I feel for you. However, these type issues typically do not leave you stranded 20 miles form the nearest sign of civilization. IME, most of the time they show up off and on and continue to get slightly longer in duration each time. Instead of being fearful, I suggest you be prepared to address the issue with some diagnostic tools while the fault is close at hand. Otherwise when the item finally fails for good, you will be walking.

It also occurs to me that this is electrical in nature. I also concur with 8166 in that the places to investigate first are the places which experience movement: ignition switch, parts of the harness around the head post, and the handlebar kill switch. Also look at your affect on those areas. Have you recently added cable ties that might beautify, but also in hindsight hinder the free movement of said cables ??

The tool of choice then would be one of these ice pick looking test lights. Easy to buy or make yourself. At the first sign of trouble, as quickly as you can, probe the input and outputs on the rear of the ignition switch and work through the ignition circuit from there. The key of course is to be prepared with 1) your test lamp and 2) by knowing where power is supposed to be when the bike is running. That means a little bit of familiarization with the tool and circuit BEFORE you leave the safety of your garage.

Good luck.

I had a similar problem on an R100/7. It turned out to be a stress fractured female spade connector in the block where the starter relay plugs in on the left side of the frame backbone, under the fuel tank. More specificly, the connector on the red wire that runs from the battery on that model. It started out as an intermittent cut-out as described, and quickly digressed to a complete failure that left me stranded. And, it was very difficult to pin-point.
Just a suggestion base on personal experience.

Thanks all.

The big problem of finding it, is that it only cuts out for a second, literally. I was out Saturday for a 100 + mile ride and it only happened once, and early in the ride, the engine was warmed up by then, so not a cold engine issue. I did some hard accelerations to see if it did it under load but nothing.

I have some work I'll be doing in the next few weeks, so I'll be checking the electrical.

Eric

Knowing just enough to be dangerous, Looking at my wiring diagram, with an electronic tach, if the cut out was caused by a faulty coil or ignition control unit would my tach go to zero at the same time? The duration of the cutout is so brief I'm stabbing at anything. I'll do a complete connection check and cleaning tomorrow..

Thanks again.

Check your battery connections, especially the ground cable, at both ends.

On my '79 RT I just located a fault I suspected for weeks might be issues with a borrowed fuel cap not breathing. Turns out the ignition switch heats up and stops making contact. Turning the ignition OFF, then back ON puts me right back on the road.

Had a similar problem on a 1981 R100. After it finally completely failed, I found it was the Hall sensor in the ignition can. Sensor is pretty cheap - just takes some time to change.

Thanks, my cutout really only lasts seconds, 2 maybe, just enough to know something happened then the rest of the ride it's ok. I went over the connections and I did discover a lose spark plug. I'm taking it out tomorrow and see if still happens

Eric

A little more info; it seems to happen with in 5 minutes into a ride. Then I dont noticed it again. Yesterday, I paid attention to the tach when it happened, the needle swung thru about 800 rpm loss from 3100 rpm, the road speed DID NOT drop an equivalent amount. It happened twice in quick succession. So I don't believe it's furl related. I'll be rechecking connections. So do I replace all of the ignition components and call it a day? Or??? Ugh!

Thanks

This is the same problem I had with my '81 R100. The tach would go crazy, the engine would cut out, and also the headlights would dim. The tach is what led me to the Hall Effect sensor in the ignition unit. I found a part number for the sensor on one of the forums and had to order it out of New Jersey - I believe at that time it costs about $9.00.
After replacing it, I never had another problem with it.
Don

I ended up replacing the ignition can myself and the problem was cured. Seemed to be the hall sensor.

A friend has told me that on his particular bike, it was the connector joining the hall effect board, not the electronic components themselves. He cut the connector off the harness and hall effect lead, then soldered the wires together without the connector.

The problem is, and not many people think about this... The hall effect devices are really only tiny generators (spinning a magnet in the close proximity of a small coil to produce a voltage spike with which to trigger the spark). The voltage produced is typically only 1.5V to 3V. So the wiring and connectors have to be absolutely perfect, or that small voltage is lost in the resistance of the faulty connection. If normal 12V connections need to be nearly perfect to work, then think about how much more 1/4 that voltage needs !!

Ohm's Law is not a suggestion. 😆

I'm using a Boyer which has performed flawlessly, except for one time on each trip the ignition quits. I've learned that the CPU in the digital Boyer cannot loose power even for an instant, or the CPU inside the ignition module has to reboot. And that's how long the issue would last, about 7-10 seconds per episode.

I know very few of you are using Boyer, but today I found a probable cause of interest to everyone. The RH choke cable may have been bouncing up and shorting against one or both of the coil terminals as it crosses over the top of the engine. There was a burned area in the plastic sheath on the cable corresponding to the terminal locations. So I slipped a 4" piece of fuel line over the choke cable which should stop all that nonsense.

A pretty neat fix I thought. 😛