Forum bmwbike.com

I recently set up the ignition on my R69S as per all the articles re Arbritz etc, and the bike started and ran better than ever. Suddenly it now dies after about 10 km. If allowed to cool it will start and just about get me home. The coil is new and checks out OK - 26.8KOhms on the secondary and zero on the primary. The points and capaciter are new, as are the plugs and the advance/retard unit. Am I missing something or has anyone else heard of this?

Where did you get that coil and is it a new plastic-cased coil or is it rewound original coil?
It has the symptoms of an old coil with failing insulation on the windings. And I don't think that new coils weaken and come back like that; I think they fail completely.
I did not know it was possible to test a coil, and besides, a cold test would not find the shorted windings that happen in a hot coil.
For the meantime, you may be able to extend the range after restarting by leaving the front cover off and riding with the coil exposed to the airstream.

Hallo ,
zero ohms in the primary?There must be something about 10 ohm. I think you will have it and you have only forgotten to reduce the range of the ohmmeter, but test it again.
You (better your cycle) have the symptoms of a bad coil or capaciter, they could be bad, even when new.
rolf

Hi Allen, thanks for the reply. The coil is from Motorworks and is plastic, and is the second fitted in three years, the first went open circuit on the secondary as did the original. You can test the secondary winding by simply measuring the resistance between the two plug leads. Each plug is connected to one end of the secondary and NOT down to earth as in a normal coil. All the ones I have measured when OK are about 26 - 27 KOhms. I tested the coil immediately on breakdown and it seemed OK. You are absolutly right to suggest leaving the cover off, that is how I got home. All I have done is to dismantle, clean and very carefully reset the ignition system using the same components The bike was running OK prior to this but did not start anywhere near as well. Pehaps coincedence? I'll keep trying,
regards, Alun

Hi Rolf. You are right, I will check it all again. I agree it does sound like coil failure but it does not show the same measurments as the last two coil failures I have had.
Regards, Alun.

Hallo,
are you sure that you havn`t any ignition when she stops? Take an extra spark plug and drive until it stops, then take that plug into the spark plug cap(?) and kick, spark or not?
Take the plug directly to the cable (without cap), also?
If there is a spark , I think it could be no fuel, because the filler cap was plugged. open the tank and drive again.
rolf
What was the exactly symptoms before it stops?

You've been reading my mind! There is absolutely no warning, it cuts out completely on both cylinders which leads me to think ignition, plus I cannot get a spark until it cools. I tried undoing the fuel cap just in case. Iv'e tried a new capacitor but the result was the same. I am coming to the conclusion it must be the coil again. I think maybe coil ingnition is on the way.

Hey Alun,
take a look to the contact-breaker.
it could be, that he was going too strong and when the engine gets hot..he pinched(?can`t move)
rolf

Alun,

I had this exact experience with a 'new" black plastic coil (Emerald Isle manufacture, I think). Apparently, a few of the early production units had some problems. Vech promptly replaced mine--only a handful of failures out of hundreds of early run coils.

Nevertheless...the replacement coil about 1600 miles ago cured the problem. I have since gotten a re-wound from Huggett and will carry the black plastic unit as a backup.

Hi Brad. Thanks for this, it goes some way to explain the problems I have had. Incedently I checked my first failed Emerald coil and this had gone open circuit on the primary and not the secondary as I thought. I ran the bike in the workshop last night and it gave up after 2 minutes, I tested the secondary immediately and it was OK but I did not have time to check the primary. I'll try again tonight.

Regards, Alun.