Electronic Ignition Module Maintenance
Here's something you're supposed to do about
once every millenium or so on your trusty BMW Airhead - apply heat sink compound
to the underside of the electronic ignition module.
Matt Parkhouse and Bob "Snowbum" Fleischer for the inspiration
for this article. Visit the
website for more information and join the Airheads!
Several esteemed Master Airhead Wrenchers
recommend performing this simple but important maintenance task about once
every 10 years or so. The post-1981 BMW motorcycles have an
electronic ignition module or system, and the module sits on top of a
A heat sink is a piece of hardware that is
used to transfer heat away from a critical component. It is used
most often with electronic or microelectronic equipment. Every
modern microprocessor, for example, uses a heat sink to help keep it cool.
If your bike runs fine when cold, but quits
after it gets hot, and you can't find any other cause, it may be that the
electronic ignition module is running too hot. Here's a simple
maintenance task that you may want to perform next time you're under the
Shack sells a small (6.5 gram) tube of Heat Sink Compound for
$1.99. This is enough to do about 30 Airheads. It's
number 276-1372; their website lists it as "heat sink
grease", but the label on the package clearly reads
"heat sink compound".
the electronic ignition module on an '84 R100RS. My '86 R65
has one in a similar position, right under the fuel tank.
The module is attached with two 7mm
bolts. After removing the bolts, you may find that you have
to tap or gently pry the module up off of the heat sink, as the
old heat sink paste will probably be pretty dried up.
the ignition module in my hand, and the heat sink. Note that
this unit apparently had heat sink compound applied at the factory
(unless someone did the maintenance, which I highly
I've heard that some early BMW
motorcycle models that used the electronic ignition did not have
any heat sink compound applied at the factory, so you may want to
check out your bike to see.
cleaned the bottom of the electronic ignition module and the heat
sink with alcohol. Then I cleaned it up a bit more with some
fine 3M Scotchbrite.
are the two pieces with the heat sink paste applied. It's
some type of inert compound that's non-toxic; I believe it's made
from silicone and zinc oxide.
Rub a thin coating on each mating
part and reattach the 7mm bolts. Once the fuel tank is off,
the whole job should take less than 5 minutes.
Be careful not to over-tighten the
bolts; they only need to be snugged up a bit.
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