1976 R90/6 Problems

new coils

So what you are suggesting is buying new coils and if so can you steer me toward a good replacement and source. According to my clymers manual my coils are not withen spec is this correct?

willyb said:

Pulled the tank and cleaned all the wire connections between the coils and still getting a nice spark to the left and nothing to the right. switched plug leads and spark followed to the right side and nothing to the left. So what is the best test for coil function although I can not imagine the coil is bad as the bike ran fine before the Alpha system install. I will check the plug in sections for the new ignition system although they seemed to attach fine when installed. Electrical system diagnosis is not my strongest talent so any step by step would be greatly appreciated as this is really frustrating. the carbs where cleaned well and working fine before all the other work was started.

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Did you actually swap plug leads at the coil.

If you suspect a coil or lead that might be breaking down internally, try temporarily reducing the corresponding spark plug gap to like .015 or so. It is surprising how low a gap will still fire - but only if the plug is clean.

I will give the plug gap suggestion a shot after I reinstall the coils.

Nobody has answered post 21 - Clymer has had this typo for years (and could somebody please verify this for us?). Trust what Kurt sez. The actual spec will depend on what coils you have, what sparkplug wires you have, and what plug caps you have. At the factory, they have used a couple of different items for each of these over the many years of production.

I repeat...…..go to a junk yard and get a VW Bug coil...…..They are all the same as BMW Rs and go for $5...……...

Coils I have are the originals, as are the plug wires. The caps are new as the new electronic ignition would not work properly with the stock plug caps.
Are the clymer specs for the ignition wrong? I do not mind buying new coils if mine are not up to spec.

It seems that you gave static resistance measurements earlier...I thought the sum of the four readings added up to the right range of resistance. Earlier in this post:

https://forums.bmwmoa.org/showthread.php?93002-1976-R90-6-Problems&p=1140536&viewfull=1#post1140536

you said you "switched plug leads" and the problem moved to the other side. So what did you switch? Did you pull the spark plug caps off of their plugs and move them to the other side? Or did you pull the high tension lead out of the coil tower and make the switch there? You're isolating different things depending on what you do.

If you just switched the spark plug caps side to side, you're still dealing with a "system" of cap-wire-coil and it would seem that one of the three items is at fault. If you switched the leads at the coil towers only, then I think you are narrowing it down to just the cap-wire.

Have you confirmed there is no corrosion inside the coil towers?

replace coils

Since you have the Alpha ignition, and NGK plug wires, why not call Rick Jones and get the Dyna single coil he sells. I replaced my old coils with the brown one and it works like a champ. Do not get the green one. He made that mistake and it didn't last 50 miles. Rick had the correct one, Brown, to my door in just a few days.

20774 said:

Looks like if you measure from cap to cap you'll get the requisite 22K ohms...I get that by adding up all of the individual ohms, leaving out the primary resistance. Doesn't mean the coils aren't breaking down in operation. Unfortunately, the only sure way to test this is to substitute known good parts...few people have coils just sitting around.

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I am one of those few. willyb should contact his air marshal to get hooked up with his local parts pirate, or perhaps send a PM to me.

Did you get your problem fixed?