Im confused about butterflies???

[Lucky_Lou]

Still tinkering trying to set the damn carbs up ive got confused by what seems to be contradictory info from the Clymer manual and info on this page
http://bmwmotorcycletech.info/bingcv.htm
the diagram of the enricher apears to be upside down compaired to the advice in the manual?? or maybe  im just plain thick (dont answer that one) clymer shows the teardrop at the top what is the correct position.....ok
confusion No2
Quote from above webpage "putting the butterfly in backwards will eliminate any chance of proper off idle performance this is doubly important with a dual plugged machine in which butterfly is more closed at idle"
Ok i understand about 1/2 to 1mm  free play on the throttle cable at idle but is this sudjesting the butterfly should be slightly open on the stop adjuster ?? presumebly this would bring in the idle jet through the two tiny holes at the bottom of the chamber. I cannot find any refferance to how far open this should be as a starting point for set up. your advice on this one would be greatly appreciated.
Lou

[Justin B.]

The throttle butterfly will never be in the absolutely closed position in a carburettor.  The cable free-play has nothing to do with the butterfly position, that is set with what is usually referred to as the "idle speed screw".

[Lucky_Lou]

The throttle butterfly will never be in the absolutely closed position in a carburettor..

yeh but how far open to start tuning??/1 turn 2 turns? must be a referance point somewhere or a vacuum amount on turnover? i think this is the key issue with these carbs as i can only start it holding a bit of throttle on and it dies if i let go.
Lou

[Barry]

It's my understanding that the butterfly when closed is not at exactly 90 deg and therfore slightly beveled at the edge so that it fits in the venturi correctly.   That is why it's important to have it the right way round.

It's also a good idea to hold a carb up to the light to check for an even ring of light around the butterfly. One of mine was not sitting centrally on the shaft and so would not fully close. I just slackened the screws slightly and moved it across.

[Justin B.]

As with the idle mixture screws there is no "correct" adjustment for these screws.  They are adjusted in combination to achieve the correct idle speed/mixture/sync.

[MrRiden]

For initial setup have the Idle stop screws, The ones that move the butterfly, turned in until they just make contact with the stop. You'll be sorting out how far to turn them in once installed and you begin to balance the carbs.
rich