Bean can

[Dizerens5]

I'm going over the whole ignition system on my 79 (originally contact breaker but some PO has fitted Boyer electronic) and I'm not clear: if I take off the bean can, is there some kind of dog clutch or whatever on the drive from camshaft, so that the position on replacing is automatically correct apart from fine adjustment? The literature I have is not clear. You understand -  I'm used to the old British technology where the ATU went on a taper therefore had to be set about right "by hand" before tapping firmly into place.

[Bob_Roller]

If you are talking about if you remove the bean can from the engine, all you need to do, is to mark the engine case and bean can to keep the timing close .

Twin cylinder BMW's use what's called the 'wasted spark' ignition system .

Both plugs fire at the same time .

The drive end of the bean can has two raised areas, that mate up to the camshaft, doesn't matter if you rotate the bean can or not after you remove it.

Impossible to get it back on incorrectly .

[montmil]

... is there some kind of dog clutch or whatever on the drive from camshaft, so that the position on replacing is automatically correct apart from fine adjustment?

Yes. The camshaft has an offset notch that engages the drive dogs on the bean can. As both the notch and dogs are offset, it is impossible to install the can incorrectly.   Monte

[Dizerens5]

Thank you - that's exactly what I needed to know!