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Alternator Pulley Cover Modification

Modification of Oilhead Alternator Pulley Cover

by Richard Rosenthal  –

I try to do as much of my own maintenance as possible on my 1996 Roadster. Partly it is out of parsimony, but in fact my closest OEM BMW dealer is 92 miles away, and anyway I really like to be able to handle routine maintenance items on my bike by myself. After all, no one in the world cares as much about my motorcycle then I do.

My maintenance chores include regular valve adjustments. I realize that some individuals can get to Top Dead Center (TDC) by putting the bike in gear and bumping the rear wheel until the correct position is obtained (using the timing chain gear markings to find same ~ which I find all but impossible to see, even when the arrow mark has been pointed out to me!) or by putting something long and relatively soft in the spark plug hole to determine when the cylinder gets to TDC). I’ve never had much luck using either of those methods. I’ve found that, for me at least, the best and simplest way to get to TDC is by using the bottom 16mm pulley nut situated under the black plastic alternator pulley cover and finding the factory TDC mark on the flywheel. The problem with this method is that it is an annoyance to take off the alternator cover to accomplish the valve adjustment job and then screw it back in place when the task is done.

I asked Duncan, of Duncan’s Beemers (located in Maynard, Massachusetts), to modify my Oilhead’s pulley cover so that a simple plug could be inserted directly over the spot where the 16mm pulley nut (which is used to turn the engine over to find TDC) is located.

Duncan took a new pulley cover (sure, I could have used the one on my bike, but I wasn’t sure this was gonna work). He found that the 16mm nut we needed to get to was directly under the BMW embossed logo on the bottom of the black plastic cover. He speculates, and I concur, that someone at BMW once had in mind doing exactly what we did. Duncan removed the logo using a 23mm hole cutter, then cleaned up the remaining excess plastic by hand. He then took a round rubber plug; a /5 fork leg bottom (part #31422000381 – the diameter of that part of the plug which holds it in place is .926″ ). The plug fits perfectly in the hole Duncan made. Now, when it comes time to do my valves, I’ll only have to pop out this small rubber plug, stick my 16mm socket inside, and go to work.

For the record, this modification was done a few months and a couple of thousand miles ago. I’ve had no problem with the rubber plug staying in place.


(click on photo or subtitle for a larger version)

Plug in place as it normally sits. The oil cooler hose naturally rests on top, making for an even more secure set-up.

A close-up of the plug, with me holding the oil cooler hose away from the area.

The rubber plug removed, showing the head of the 16mm plug, ready to turn the crankshaft.

Pic of the rubber plug, top view.

Pic of the rubber plug, bottom view.

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