Coil for 1981 R65

[YOCKYRIDES]

My 1981 R65 has a cracked coil housing.
Is there an inexpensive aftermarket replacement coil that will not require replacement of the Ignition Control Unit?
Sources, part numbers and approximate prices appreciated.
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Just found an old posting on this exact issue and a Motorad Electrik kit was recommended.
Anybody have experience with Accel? Part number?

 

[boxermaf]

Call Rick @ Motorrad Elektrik and order the Dyna Brown coil (it is actually orange in color, but the "Brown" coil is for the solid state ignition system, the Dyna Green coil is for use with points ignition). Cost is approximately 90$, and will include instructions and mounting bracket. Very easy to install. Your crack-o-matic coil problems will be over.

 

[rpeckham136133]

Many '81+ BMW's are using the Harley EVO coil, often available on eBay for $20 or so. Considered very dependable, not polarity dependent.

Harley coil 31614-83A

 

[YOCKYRIDES]

Was '81 a crossover year for parts? My 83 R65 uses a different coil, I think.

 

[rpeckham136133]

The "crossover" was the change to the electronic ignition control module, but it was done in a hybrid sort of way.... Some of the early ones used points and the icm, then they went to the Hall sensor, both inside the so-called beancan, under the front cover. And continued to use the very old-school rotating mass with springs to control the spark advance in both versions of the beancan. The Hall sensor began, I believe, in '81. At the same time, the clutch flywheel assembly got changed to the clutch-carrier assembly... so yes, there were some crossovers.

Motorrad Elektrik has a very nice "all electronic" ignition system that bolts in place of the beancan, but actually has an electronically-programmed advance curve.

Check out their website for the various and sundry parts for the range of iterations of ignition systems. Motorrad Elektric home page, be sure to poke around on the website to see their offerings. Very good things are said about their products and their service.

 

[YOCKYRIDES]

Tried finding the coil resistance (ohm) spec for 1981 R65 but it doesn't seem to be in any book I own. Anybody know?

 

[20774]

Most coils on dual-coil Airheads (at least the pre '81) have a resistance of about 5K ohms. Total resistance from one spark plug cap to the other cap plug cap is around 20-22K ohms. That's 5K per coil and 5K for the resistance in the spark plug caps (if installed).

 

[boxermaf]

I think that he wants the PRIMARY side coil resistance, which is important to know if one is using points or the solid state ignition ICU. The seconday side resistance makes little practical difference in the application. There is info on this @ snowbum's site, but basically, you want to have a 3 Ohm (or higher) primary coil resistance if using a points& condensor setup (Dyna Green coil is 3 Ohms). The solid state ICU can safely handle lower primary resistance coils, and the Dyna Brown coil recommended for use with it is between 1 and 2 Ohms resistance on the primary.

you could use a higher primary resistance coil with the solid state ICU (like using the Dyna green coil with the ICU) without any ill effects though your spark may be just slightly weaker. The points ignitions require a higher primary resistance to avoid the excessive current which could damage the points/condensor. The solid state ICU was revised slightly in the late 80s and by the 1990s the airheads were using a 12V dual output coil with approx 0.9 Ohm primary resistance.

78-80 R65 bikes used (2) 6V coils in series, but by 1981 the 12V dual output coil was used on all R65 bikes. These were the familiar dark gray "crack-o-matic" coils. If your 81-> R65 has different coils, it is likely that some PO had switched out the problematic OEM coil at some point. As indicated earlier in this thread, 1981 and later bikes all used the "beancan" Hall effect ignition trigger with mechanical advance mechanism, running the solid state ICU unit under the tank.

 

[YOCKYRIDES]

Boxermaf is correct that I wanted the primary resistance. So a 4 ohm unit should work on a solid state ignition...?

Thank you everyone for responding.

 

[boxermaf]

A 4 ohm coil can work with the solid state ignition, as it is more resistance than the ~ 2.4 ohm coil that it was designed to work with. Your spark may be just a little bit weaker than it could be with the lower primary resistance coil, but the difference may not be enough for any real world detectable difference while riding, etc.