BMW repair

[75R60]

Hey I’m in Durango Colorado midway thru a cross country ride with my R100/7 1978. It’s having electrical issues. Can anyone recommend a BMW guy between Colorado and LA?

[schrader7032]

What is it doing?

[75R60]

This is happened five times now and each time it seems we found some thing small to blame it on, but in general the bike seems to lose power, starts bucking like it’s an electrical issue, and then eventually quits. We have found pitted points, and replaced them twice. Including the condenser. We’ve adjusted timing, the valves, and in general once we’ve done that each time the bike has come back to life for another few hundred miles.

The list of issues that we have blamed each break down on are:
Loose terminal on the point wire where it connects to the condenser- This breakdown was preceded by a sudden pop and shut down. The bike literally quit immediately on the side of the road

Poorly adjusted points in timing-we’ve worked with this each time and had no success in static timing the bike. We bought a timing light and successfully timed the ignition with that. We also seem to get consistent continuity between the points in other words regardless of where the engine rotation is, the points have continuity open or closed. Points have been replaced three times. As a result we replaced the points with a Dyna three ignition system and have had a similar break down since then. Electrical sputtering and loss of instrument display, headlights and taillight which seemed to point to the starter relay.

Water in the electronics including the starter relay beneath the tank. We have ordered that and it’s arriving today. This was the latest breakdown.

[schrader7032]

Have you looked at the coils? Try reading the resistance from the left spark plug cap to the right cap. Should be 20-22K ohms. The caps themselves are 5K and each coil adds another 5K. Check that the jumper wire between the coils is solid. Also, pull the wires from the coil towers and ensure that there is no corrosion there.

And the battery is OK? I guess if you're starting it over and over, it must be fine. No lights illuminating on the instrument pod? What is the voltage at the battery terminal at an RPM of say 3000?

[srankin]

You are on the right track looking at the starter relay. I would also check ignition switch wires as well. What you may have is a loose or possibly breaking wire or connection.

I had a very similar problem with my 84 RT, starting off at first as a hiccup while riding too after a year of troubleshooting, a full blown dead bike, no power at all. Sadly, I never did find the smoking gun causing the problem. I did find however that swapping out parts such as the bean can, ignition module, ignition switch and starter relay didn't fix the problem at all. Most likely the solution was just plain checking connections both hot and ground in the system.

While I understand this does not help you much, I guess I am trying to say, don't get carried away with buying new parts until you check the simple cheap stuff first. A loose connection on the ignition switch is a lot cheaper to fix than buying a new one.

EME sells very good large wiring diagrams and to be honest, I would not begin to try to troubleshoot electrical problems with out a good wiring diagram and understanding of the electrical system.

Good luck, I know it is a royal pain to find intermittent electrical problems. Hopefully you get luckier than I was and find something simple cheap and quickly to solve the problem. St.

[75R60]

Thank you guys again for your insight. The starter relay came in this morning from EME. We plugged it in and Wala the bike seems to be running well. I’ll do another follow up on this once we get to our destination in 1500 miles

[srankin]

It is nice to find a solution to a problem that doesn't take a lot of time to fix. Thanks for letting us know what you have found. St.

[Armand]

Maybe I’m wrong but starter relays relate to starting the bike. A bad one won’t cause the bike to quit once it’s started.
Coils and or bad wire connections are my top bets. When coils get hot,they start doing what the op described.

[75R60]

Thanks for your insight Armand. It’s been 1000 miles and the bike has been faithful. The relay also affects the Power to the headlights and tail lights switches as well as the blinkers. Oh and dash assembly. Everything has been good since replacing the relay. To Schraders point, I did test impedance across the coils and it was 23,000 ohms. Outside of the tolerance I believe it may be a clue that something needs to be done with them.

[schrader7032]

23K ohms on that measurement sounds just fine. I think the tolerances I gave have a certainly amount of fuzziness in them. If the reading was 15K or 40K, then that's clearly a problem.