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1982 R100RS with an intermittent ignition problem: Runs fine and then no spark in both plugs. replaced the ignition control unit and harness because it seemed to have a intermittent connection. No joy. Checked all the wires and connections visibly, seems good. Wiggled wires and can't seem to find a problem. cleaned the coil connections and disconnected all the electrical plugs.

I have a spare ignition unit to try but don't know the initial timing procedure used if you don't have the tester mentioned in the BMW shop manual.
Is there a way to static time the unit without the tester??

Any one have any other suggestions?

Do you still have the kill switch? Several have found that bad connections at the switch can cause this symptom. Just a thought that is fairly easy to check, but you probably already did.

when I hit the kill switch the starter doesn't work, when the bike dies or looses spark, the starter still works, just no spark.

I was going to say heat sink paste but that is for situations where it works for a while and then it doesn't. Not sure how that would affect starting. But be sure the paste is renewed under the ignition module.

Kurt in S.A.

BMWARCHER wrote: I have a spare ignition unit to try but don't know the initial timing procedure used if you don't have the tester mentioned in the BMW shop manual.
Is there a way to static time the unit without the tester??

Any one have any other suggestions?

Mark the position of the ignition can before you remove it, then just install the substitute to the same position. It'll be close enough I expect.

A couple of things I found with strange ignition symptoms....The battery connections can be the culprit, if just slightly loose, or rubbed through earthing somewhere on the frame. Likewise the ignition switch itself, with the barrel for the keys being worn just enough to momentarily lose continuity. Where the power lead exits the top of the crankcase just in front of the starter motor cover, can wear and earth out on the case. The red wire from the diode bord to the starter solenoid can be faulty as well. Sometimes it only happens when the bike is hot, never when idling on the stand, or over bumps and corrugations. Spark plugs or leads ( or both) shorting intermittently ( have you looked at the heads at night for signs of blue sparking around the lead caps??) Had all these problems myself in 25 years of the same bike with 3/4 million kays on it, and nearly drove myself mad trying to diagnose what was wrong. Just keep looking; you will find the culprit eventually

Thanks for all the advice!

Checked all the connections, renewed the heat sink paste, cleaned out a massive amount of green copper corrosion from the coil towers and replaced the ignition unit.

The ignition unit was the culprit. The input shaft was very stiff to turn.

I've had this bike since 1984 and over 125,000 miles and am anxious to ride it some more. It has taken a back to a new KTM RC8 and a KTM 450 EXCR dual sporter for a while.

Again thanks!

BMW archer, congratulations, doesn't it feel good to finally find and fix something so annoying?

Your quest helps us all learn more about symptoms, diagnostic tools and diligence.

BMWARCHER wrote:Thanks for all the advice!

Checked all the connections, renewed the heat sink paste, cleaned out a massive amount of green copper corrosion from the coil towers and replaced the ignition unit.

The ignition unit was the culprit. The input shaft was very stiff to turn.

I've had this bike since 1984 and over 125,000 miles and am anxious to ride it some more. It has taken a back to a new KTM RC8 and a KTM 450 EXCR dual sporter for a while.

Again thanks!

Well, BMWarcher, you have all the bases covered well. KTM.ARCHER now?

KTMARCHER on KTM forums,ELKARCHER on archery hunting forums, BULTACOARCHER on desert racing forums-district 37 AMA