ok, this may seem obvious question but I am having a bit of trouble setting up a smooth idle and I am wondering if I am doing something stupid by misreading the manual!

what is the starting setting for adjusting idle mixure screws? The manual says 3/4 from fully in, am I reading this right - as thee quarter turns from fully in, or does it mean 3 to 4 turns. Also which way does the ajustment work i.e does moving the screw in make the mixure richer or leaner?

hi,
starting point is three quarters of a turn from fully in
moving the screw in makes mixture leaner

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Thanks Patta

Snowbums website is not short on detail when it comes to tweaking carbies

Synchronizing BMW Airhead Motorcycle Carburetors

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I'm having some problems setting mine up too...just cleaned both carbs and changed all o-rings etc, including the one on the butterfly shaft on my right hand Bing ..I suspect that I may have left too large an opening when reseating the butterfly, but I was playing around for ages getting it to seat in the position that seemed best (least light visible when pointed towards the light)

the bike runs perfectly well off idle, however the annoying thing is that I just can't get it to idle smoothly. I can screw both mixture screws right in (more so on the right side), and the bike will just start to surge like crazy. I've sprayed brake cleaner all around, with the engine running and it doesn't seem to have any obvious leaks. There's no dying point at all, and I've settled for a slightly high idle, unscrewing the throttle stop screws until they're barely toughing the cable stops.

It runs ok with both screws 1 turn and 1 1/2 turns out, there's good engine braking , and I'm just going to leave it that way...but that surging when I screw in just bothers me...isn't it supposed to kill the engine when I do that?

And yes, I can confirm to the OP that the mixture screw is actually a Fuel screw, unscrewing = richer idle mixture
Sorry for the hijack. Thanks for any hints. the bike is an r 80 G/S by the way....!

Before you play with the carburettor adjustments check both the tappets and ignition timing. If either is wrong you will never get them right.

Yes you are .

Too many possible problem steps omitted in your description.

First of all - you will not get even close to the perfection achived by using the hydraulic calibration system. Forget gauges!

You must also be sure that there is not leakage of air in any of the possible (and not possible) steps that will affect the idling...

Get the tuning manual from Bing USA - it is worth every cent!
Bing Manual

or you could stop by my friend in Sandviken, Sweden, and he'll do it for you: www.midland.se

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1)
Check Valve setting.
2)
Check Timing.
3)
Ride at least 20km.

Make sure you have 0.3mm slack in throttle cables.

4a)
Sync carbies @ 1,050 RPM using a sync meter
4b)
Turn one mixture screw to the left (rich) until engine runs rough, then to the right (lean( until the engine runs rough, take mid-point (repeat if you want)
4c)
Same for other mixture screw.
5)
Check sync of carbies, repeat 4a-c if you are manic obsessive.
6)
Open throttle to 1,500 revs, adjust throttle screws observing sync meter.
7)
Make sure throttle cable slack is still 0.3mm or so.

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