"Bean Can" reassembly

[svejkovat]

I did not mark or photograph this when taking it apart. This dog gear can be mounted to the shaft 180 degrees from original. Does it matter? The slots for the Hall sensor are 180 degrees. So either way is fine?

Or can someone help me determine the right choice?

IMG_20240704_114648904.jpg (5).png (761.28 KiB) Viewed 413 times

[svejkovat]

And for trivia's sake.. why are the dog teeth (and corresponding slots of course) designed off center like that?

1983 R65 std (non LS) by the way.

[melville]

That drive dog is also used on VW distributors and probably others. The orientation of it can be important in applications without the wasted spark as used on Airheads.

I don't think it will make a difference on an Airhead bean can.

[Rob Frankham]

Yes, it does make a difference.

The camshaft, and therefore the bean can mechism, turns at half engine speed so. with the dog clutch assembled 180 degrees out, the engine will be getting a spark around TDC at the end of the exhaust stroke. Can't help on a quick and easy way to determine the right way up if it isn't marked because I'm away from home at present. Can work it out when I get home in the middle of next week if you're still in the dark...

The dog teeth are offset so that the 'can' can only be located to the camshaft the right way up.

Rob

Edit... total nonsense by me, it makes no difference... apologies for this

Rob

[svejkovat]

I'm struggling with the mechanics on that. This can disassembled on my table has two slots in the rotating sleeve, 180 degrees apart, that trigger the Hall sensor. Members at another forum confirmed that their points equipped cans have two cams, 180 degrees apart, on the shaft. If so, rotation at 1/2 rpm should have no effect if the dog gear is mounted either way? But I agree with your reasoning for the offset dog teeth. BMW maintains that the can is not a "serviceable" part. So if it was never intended to be disassembled, that orientation would certainly assure that it was installed in the proper "phase". Which, maddeningly now, suggests there is a proper one to begin with.

[svejkovat]

"That drive dog is also used on VW distributors and probably others. The orientation of it can be important in applications without the wasted spark as used on Airheads."

That didn't register at first. But I think you got it there. I looked at the Beetle drive dog online and it's appears identical. That would definitely be a reasonable explanation.

In answer to the spark occurring at the exhaust stroke... it is in any case with a wasted spark system. No?

Thanks

[melville]

I'm struggling with the mechanics on that. This can disassembled on my table has two slots in the rotating sleeve, 180 degrees apart, that trigger the Hall sensor. Members at another forum confirmed that their points equipped cans have two cams, 180 degrees apart, on the shaft. If so, rotation at 1/2 rpm should have no effect if the dog gear is mounted either way? But I agree with your reasoning for the offset dog teeth. BMW maintains that the can is not a "serviceable" part. So if it was never intended to be disassembled, that orientation would certainly assure that it was installed in the proper "phase". Which, maddeningly now, suggests there is a proper one to begin with.

Exactly. I think the points open in the same places regardless of where the drive dog goes.

[gspd]

For our airheads it makes absolutely no difference which way the slots are oriented.
On a 4 cylinder VW, it makes a difference. If it's installed wrong on a VW, the ignition rotor will be firing number 4 cylinder when it should be firing number 1 cylinder.