Vintage BMW Motorcycle Owners

Got the engine running, finally.
Starts and accelerates ok.
How can I fine tune each side in terms of air/fuel mixture, if it is forbidden to pull the plug wires on each side while the engine is running (equipped with PowerDynamo electric ignition/charging system)?
I do not want to come up with a mixture that is too lean and cause the engine to over heat.
I also do not want a too rich mixture...

Edit:
Came back from a short ride, the bike is not a first kick starter, but once running, it is responding & pulling very well.
It needs about 10 kicks and a bit open throttle to catch. Would like it to be a first kicker.
I have an EMPI Universal Pro-Sync.

Carb spec's for Bing 1/22/61-62
main jet 105
idle jet 40
needle jet position #1 top (yours look like #2 in previous post photo)


Shorten spark plug
Old wheel spoke and shorting jumper
note:
Always ground jumper 1st then connect other side to plug wire








Merry Christmas
Tommy

Thanks a lot Tommy .

I have one question: Engine idles well but will die when opening throttle.
Is this a sign for a too lean mixture, or a too rich mix?

EDIT
Got it starting easily but right side is smoking white grey smoke, while the other is not smoking.
I can't get the EMPI synchro tool to read both side the same.
One side reads 3 while the other is 5. How important is the uniformity between the two sides in these old engines?

2 pictures of the left side plug and then 3 right side smoky plug on cardboard background :

Michael,

The right one is washed with fuel and is very rich. The left looks rich but is firing and looks to be running and if your idling for a while it can look that way even with decent mixture.

Sorry to say but it looks like your right carb has an issue. Do you have another one sitting around? As I remember you had purchased new carbs. I might try the old one on the right.

I also seem to remember that you were using a sonic cleaner. I used to use one as well and I have stopped as I am not sure how it affects the internals of the older carbs. It is very possibly fine but I am not sure.

You stated:


How can I fine tune each side in terms of air/fuel mixture, if it is forbidden to pull the plug wires on each side while the engine is running (equipped with PowerDynamo electric ignition/charging system)?

There is a way to do this, without damaging the electronic ignition. Find a couple of brass thread on ends, that come (or used to come) on new spark plugs and solder a brass rod on the end of each one.
You then thread one on the end of each spark plug, and place the plug cap on the end of the brass rod.

You can then start the engine, and have a buddy with a well insulated screwdriver, touch the head and while doing so, then lean the screwdriver over and touch and hold it on the brass shaft. That will kill the one cylinder, and give the ignition a place to discharge without any damage.
And you can then set the idle air mix correctly, the same way one does with the original magneto ignition.

Thanks Vech, will give it a try this weekend.

jwonder wrote: ↑

Sat Dec 25, 2021 9:30 am

The left looks rich but is firing and looks to be running and if your idling for a while it can look that way even with decent mixture.

Love the kernels of experience shared in this forum. This ^^ is a great example.

After installing a new ATU, setting my timing, valves, syncing my carbs, I take a look at my plugs after a decent ride. Right side looks perfect and left side is a bit sooty. Crap, I start running thru possible things to check when I remember this post. My old routine when I get home from my rides was to shut off my fuel, put my bike idling on the sidestand to empty the bowl, and walk away to open two side gates and my shop door. Just takes a minute to get back to the bike and wheel it in, sometimes still idling, sometimes it’s used all the fuel. So … remembering this post, I clean up the plug and go for a ride up a nice little grade, up in the revs nicely in 3rd. As I near the top I pulled the clutch in, killed the motor, coasted to a stop and put it on the centerstand. Checked plugs and they looked beautiful and identical.

Long winded way to say thanks James, in this case, but also to all who share tips and experiences here.