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1978 R/100 electrical question?


Beemer Dave

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Beemer Dave

Hey BMW nation! 

I was wondering if I could get a little help? I have completely restored (frame up) a 1978 R100 Airhead and I am on the final leg of the race to be able to ride her down the road. Yesterday I found a small problem and was hoping one of you kind folks might be able to help? During my build I decided to install an electronic ignition system and do away with the points set up. The ignition I went with is from Euro Moto Electrics and I bought it from Bobs BMW of Maryland. The bike idles amazing but when I feed her the onions she falls flat on her face, naturally I assumed timing. I connected my timing light to the left side plug wire and fired the airhead up. The strobe from the light was speratic and very intermediate. At first I figured it was the timing light, but before going to buy a new light I hooked the light to the right side plug wire and the light worked perfectly. I called Euro Moto Electrics and a kind gentleman asked if I had resistant or non-resistant plugs in the bike. He explained that the ignition would not work properly with resistant plugs, and per my inspection of the plug I had in the bike there was the letter "R" in the part number. I ordered a set of NGK non-resistant plugs, but honestly..... is this an actual thing? I was hoping to hear from some of you that may have had this issue in the past? I really appreciate any information at all. Thank you for taking the time!

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dirtrider
3 hours ago, Beemer Dave said:

Hey BMW nation! 

I was wondering if I could get a little help? I have completely restored (frame up) a 1978 R100 Airhead and I am on the final leg of the race to be able to ride her down the road. Yesterday I found a small problem and was hoping one of you kind folks might be able to help? During my build I decided to install an electronic ignition system and do away with the points set up. The ignition I went with is from Euro Moto Electrics and I bought it from Bobs BMW of Maryland. The bike idles amazing but when I feed her the onions she falls flat on her face, naturally I assumed timing. I connected my timing light to the left side plug wire and fired the airhead up. The strobe from the light was speratic and very intermediate. At first I figured it was the timing light, but before going to buy a new light I hooked the light to the right side plug wire and the light worked perfectly. I called Euro Moto Electrics and a kind gentleman asked if I had resistant or non-resistant plugs in the bike. He explained that the ignition would not work properly with resistant plugs, and per my inspection of the plug I had in the bike there was the letter "R" in the part number. I ordered a set of NGK non-resistant plugs, but honestly..... is this an actual thing? I was hoping to hear from some of you that may have had this issue in the past? I really appreciate any information at all. Thank you for taking the time!

Afternoon Dave

 

Resistor or air gap type spark plugs usually don't cause timing light issues (your T- light probably works OK on most automobiles & those almost all use resistor plugs). Resistor spark plug WIRES can cause timing light issues on some timing lights.  

 

What I have seen is some timing lights need the pickup installed in a certain direction (some even say  arrow towards spark plug).  

 

On the BMW with a 180° firing order one side fires reverse so the first thing to try is reversing the T-light pick up on the side that doesn't work correctly.  

 

 

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