Looking hard at the RH throttle control, which contains the balance screw, and actuating levers both left and right carbs, I am puzzled by the gap between the actuating levers. The left hand butterfly opens first before the actuating lever closes the gap mentioned and actuates the right hand butterfly. So therefore when operating the hand throttle (OR closing the idle throttle screw), all one is doing is opening the RH butterfly at first, unless the butterfly is pre-opened closing the balance screw, which serves merely to pre-open the RH butterfly, by up to about 4 mm. A balanced state at assembly and for idle can be attained by slackening off the balance screw, but How can a balanced state of air flow be achieved therefore, at higher ranges?
SPot on Sev. Thanks. I looked closer, and suspected the something was missing to close the gap, and after a search for image online, found that it was the top spring, that I had left out after replacing a cracked T-piece. I still had the spring, but wasn't sure where it went. PUt it back on, and all is fine now. The mechanism to balance the throttles with the advantage of a single cable, is ingenious. Must haver taken a lot of trial and error - more than mere maths - to get the posts and springs right. I see that the top spring (the lighter spring of two pushed the lh hand throttle shut and closes the gap at the rh throttle lever. In fact, it seems as if it slightly opens the LH throttle by a fraction of a millimetre. Then, as the carb is tuned with the screw, the lh throttle catches up the rh, and eventually overtakes it.
Well. you are a nit, then.....you should have asked the expert on SS carbs. Me! BTW.....'expert' means a drip under pressure.
Yep, true I did think of posting a question, and i think of you... but i feel like a pest because ive contributed so little other than ‘likes’. I also put in new main and needle jets so i started by investigating mixture, air leaks, pilot screws and cables before investigated throttle mechanism per se, which led to my observation...... but having completely forgotten about the extra spring I’d found, because to tell the truth, there are small springs everywhere around me, my son likes springs and designing missile launchers and foot pressure spy mechanisms with them. I have a few springs myself... The missing spring must have jumped when I seperated the carbs, didnt suspect two were required (not in my exploded BDST diagram ) but put that spring in tin of miscel spars, Luckily. Yeah, im a nit, spent a lot of time puzzling on that. Trust all’s well have been enjoying riding. Still got the piston slap on horizontal. I wonder if it pits a strain on small end... must do, surely?
Cheers Sev - most perceptive and kind of you to clarify that particular point; yeah i had that clear on the picture i found, and it was stated as fact in the article source - a comprehensive write up with very clear photos, on a BDST twin carb rebuild. I could find the link, its a US carb supplier... Also, i while I was at it I wrote a clear outline of solving hanging high idle, I think its a good start - I could submit it for improvement if a sticky for thst would be a good idea. Let me know.
There are a number of silly things that can cause a hanging throttle as it settles to idle. 1) The twistgrip rubber flange binds against the actual plastic cable housing. 2) The idle adjustment is a bit too high - bring it down to around a 1000 rpm and work back up so it is about 1050 - 1100 max. 3) The spring between the two carbs is all fouled up with crap - needs cleaning and lubricating. 4) The choke mechanism is sticking because of crap on the slider bar - needs cleaning and lubricating. 5) The choke cable is too tightly adjusted - or wrongly routed. 6) The throttle cables don't have enough free play in their adjustment. 7) The 'return' cable needs slightly less free play than the open 'throttle' cable - so it pulls the twistgrip back quicker. Etc, etc, etc.
