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Intermittent Ignition cyl 2 - No sign of vacuum leak 1978 CB750 K8

Ahh shoot my bad went back to size 35. Anyways went back to the 40.

I cut the ends of the wire and recrimped, still had the same issue. so I swapped the ignition coils. And then the same issue appeared on 1 or 4 with the 1/4 spark plug wires attached. depending on which wire was attached. so essentially three different wires had the same issue and it seems like it is all out of the same port on the ignition coil. I assumed the two ports were wired together? The coils were replaced recently so maybe I have a dud?


Have you seen this happen before?


The floats all look identical but I will try throwing one of the old ones back in or ordering a new one
 
Ah my bad #35.

Finally received new coils and now all 4 cylinders are working. So far this is the happiest i've seen the bike

I had to adjust my mixture screws with the additional cylinder burning gas every stroke instead of every few.


I was able to get reasonable throttle response out of a #35 pilot but the #40 with the screws all the way seemed a bit better. (although at idle this is very rich looking at the colortune and the rich smell is very noticeable) It does lean out once the RPMs go up though

Is there any overlap in the ranges of the pilot screws or should I order a #38, Would it also be smart to get a digital tach to help with adjustment? I'm currently doing it by ear and testing the throttle in increments


Currently when I blip the throttle fast the bike hesitates than catches up after I back off. If I do it a touch slower it seems fine. Looking at the colortune it goes from rich to completely lean to the point where I can see the combustion stop when the throttle is opened up quickly. The Accell pump is working and the backflow valve on it is not jammed open.

Any suggestions on getting the engine more fuel? or do these bikes just not like to be blipped?
 
If it hesitates with the stock jets then more then likely the accelerator pump is working correct on all 4 carbs. Check make sure you have a squirt out of all 4.
 
Accel pump 100% works on all 4. I am able to squirt fuel right out the front of the carbs when I have it out of the bike. I have heard people have some luck with the older carbs without the Accel pump. If they raise the needle.

Would that actually help or just cause other issues if I shimmed the needles?
 
If there is even the slightest bit of slack in pump linkage you can get a balk even if the pump is working right. It must work instantly.

Engine condition can in unusual conditions make a balk too, slow timing, engine in less than good shape, plugs black from fouling due to not sparking can do it too. If not a pure carb problem only, then it can balk due to engine refusing for a second to take the opening throttle due to something wrong with it.
 
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