Topic: Carbs, yes I've searched and read and read but no answers to my questions yet!

[CB750R]

Ya ok its another carb question, ya its pods,  full tune up, fresh engine rebuild, timing timed running a dyna S,  fires up super easy, but part throttle around town, less than half throttle is surging, and back fires on decelleration, get outa town and wind it out it feels great but then seems to lean out at speed, anything past half throttle power fades out.  I was on 115, then 124, now 128s for main jets. Emulsion tubes and pilot jets are squeaky clean so no problem there.  has anyone had issues with the pod rubbers not fitting well and almost causing a reverse velocity stack shape to them??  My plug chop attemps were confussing, I have a loooooong ass hill here thats perfect, but my WOT chop the plug looked as clean as it went in. my guess is still too lean, but why does it feel so good winding through the gears, and soo surging/popping on decell around town?  Oh ya I'm running the 77F carbs on a 74 motor. just to make it more interesting...

the only jets available in my little town here are from my friends mukuni, jet kit for his bike, the jets have the same thread and shape of the kehiens that I've pulled out, or am I commiting a major carb sin here?  I figured I'd use his jets to get me in teh ball park then order some specific ones for kehien when I have an idea where to go...

Am is still lean?? and need to go bigger?  or is there something you guys see here that indicates I've got other things to fiddle with? 

[TwoTired]

Somebody here said that mikuni jets were numbered from flow results vs. the Keihin mm numbering system.

Did your search uncover the chart below?
You may have to change more than just your main jet.

Have you marked your thottle to know the precise throttle setting where objections are noted?

Cheers,

[scondon]

If you've already synched your carbs and checked for air leaks I would...

Clean the pilot circuit which involves removing the pilot jets and fuel mixture screws(spring,washer and o-ring on each screw) and flushing copious amounts of carb cleaner through the pilot jet orifice, fuel screw orifice and air jet(located in the air intake of each carb). Once you are certain that the pilot circuits are clean then you can reassemble and adjust your fuel mixture screws to reduce or eliminate the popping on decelleration. Having just one circuit that is partially blocked can throw things out of whack.

My guess is still too lean, but why does it feel so good winding through the gears.

    The 77 carbs have a accelerator pump that squirts fuel into each carb throat when the throttle is twisted. Usually there is plenty of throttle twisting when winding up through the gears. Hold the throttle steady and you are no longer getting that extra fuel.

has anyone had issues with the pod rubbers not fitting well and almost causing a reverse velocity stack shape to them?? 

    Make sure your pods are for the 77-78 carbs as they have a bigger diameter to fit the larger air intakes. If your squeezing on pods from earlier carbs I imagine they would distort somewhat.

My plug chop attemps were confussing, I have a loooooong ass hill here thats perfect, but my WOT chop the plug looked as clean as it went in. my guess is still too lean

   If your plug chop was done in 4th gear at WOT(1/4 - 1/2 mile) then I would start looking at other things. Too lean leaves a definite white,chalky deposit on the plug.


   The chart that TT dug up for you should help you make some decision as to what needs tuning(jets, needles), but only after you've cleaned, synched and checked for air leaks.

    Keihin jets can be bought here....

http://www.crc2onlinecatalog.com/misc_carb_parts.htm#Main%20Jets

[CB750R]

thanks so far for the input, I'm going to take the pods off, I have a sneeky suspicion they may be interferring with the air jets on the mouth of the carb, not directly mind you but the lip the smaller pod rubber I think is causing a dead spot in air flow that may hamper things, I'm off to work, hopefully I'll have some positive news tonight.   I have seen that chart thanks, for that, I have taped lines onto my throttle to help diagnose where issues are.  my hill here is at least a half mile, and no white chaulkyness on the plugs so I'm obvoiusly not in the DANGER zone, but definatly not in the sweet spot yet either!!  Rings, pistons, conrods, assembling the head, nooo problem, tuning a carb, man thats the test of a home mechanic!!

[eldar]

if you have the 77 carbs, then you should have the slots on the needles yet. Drop the clip one slot to raise the needle, that might help you lean running.
 
Also have you tuned your idle mix with a shop tach? Best way to do it. I dont really trust the "ear" method.