TOPIC:

I have a set of keilin cv34 carbs of a 82 750E2 on my 78 650. I have kept the 750 stock air box with a Uni filter, and every thing works well, except the main secondary venturi system bogs out the engine. I was going to drop my secondary jets down from 125 to 107.5 to see if this would solve the problem. 107.5 is the standard jetting of a 650 with this air system. Does any one know if this will disrupt the venturi effect of the 1/2 to full throtle position?
Thanks Rev

Rev, I sure don't have any idea how to answer your question but if I do understand you right, your bike doesn't run well on the current jetting. You state that the "main secondary venturi system bogs out the engine"... Can you reword your problem a different way? In other words, your bike has operation problems. At what speeds/conditions do these problems occur and exactly what happens... you mention bog... does that mean it accelerates poorly at some rpm. How does the bike start, idle, pull away from stop (the off-idle transition) and what how does the bike perform in mid-range (as in passing) and wide open throttle?

By the way, you only have ONE venturi "system" in your carbs. That is the big hole going through them. The Secondary main jet size controls wide open throttle operation when the jet needle is out of the needle jet (slides raised). The "main jet" continues to have some effect in Keihin carbs even at wide open throttle as does the pilot jet but the main jet is mainly contributing to the mid-range performance. Knowing HOW the bike performs and exactly where the problem is will allow someone to guess if you need a different secondary mains, mains or pilot jets.

Thanks WiredGeorge for the clarification on the venturi, I was just going by what a mechanic was trying to tell me. The bike works fairly well when I take off from idle, and when I slowly open up the throttle to about 1/2 throttle. Opening up the throttle any more than this or when I just crank on it, the bike does not respond until I back off and open it up slowly. When I let the motor pull it self up to 8 grand it responds very well, but if I try to just crank it will accelerate very poorly leaving behind the scent of a very rich mixture. I am also having to clean the black carbon off the plugs once a week, or more to keep it running well. And as for starting, it comes to life at first touch of the starter switch.
Considering that the carbs were off a 82 Kz 750 E2, my thinking is to lower the jets down to a more reasonable setting for a Kz 650. Presently they have a #62 jet for the primary, and a 120 for the secondary. I was going to drop them down to 57 for the primary and 107.5 for the secondary. Would this be to drastic or should I only go down to 60 prim, and 117.5 for secondary which I believe is the lowest setting for a the 750? I know right now it runs away to rich.
Thanks Bill