Engine randomly missing

[pat_in_the_hat]

Alright. Pretty sure its a carb related issue.
But, when it sits and idles, the left cylinder will miss fire randomly (roughly every 15 seconds). It continues to run, just misses once, then acts like nothing happened.
But whenever im applying any throttle it runs great, its just when idling.
Since its the low end, its related to pilot jet, right? im pretty sure ive tried adjusting it to every possible adjustment without getting rid of the miss fire.
What else could it be?
Could it possibly be the coil?

Im about to give up and take it to a shop to get adjusted. Im just nervous about them finding all my work and saying its a piece of shit hah

 

[pat_in_the_hat]

it woudnt be a spark plug problem, would it? since it still fires, just misses once in a while.

 

[bikefreak69]

I am no expert but I don't think it is a spark issue, my BS 38 carbs are very sensitive to fuel screw adjustment and the timing with the Pamco ignition is also very sensitive to adjustment. I think it could be that the carbs are not quite synchronized and therefore the butterflies not being exactly aligned may have something to do with your slight miss at idle.

 

[CDNTX650]

I have been going through this myself, same deal. Its sync. My left pipe would flubber a bit at idle if you really listened for it, vac guage looks the same for both.. So i did it by ear. Slow the right side downn hair with the sync screw. Very very touchy and hard to get exactly even. Suppose its nature of the beast....it aint efi.

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[pat_in_the_hat]

yup, you are right, it is the sync. I tried to adjust the slides closer to each other. The miss is not as frequent now, but it still happens once in a blue moon. So they must still be off a bit, but thats what was causing it.

Thanks for the help!

 

[jonboy-xsbobber]

I have the same problem with the left cylinder missing I just got new Mikuni vm 34 round slides and the left is still missing at idle haven't tuned the new carbs yet but thought it was weird that the same cylinder would still be missing any thoughts?

 

[pat_in_the_hat]

from what ive read, its due to the carbs not being perfectly synced. One ends up being open more, thus running faster and choking out the other carb (i believe)

 

[weekendrider]

pat in the hat, what is your idle speed?

 

[pat_in_the_hat]

i dont know the exact idle speed as i dont have a tach. But it only happens when it is idled down without any throttle. And I noticed it only does it if it sits for at least 10 seconds or so. Then it does it randomly.

 

[weekendrider]

Try turning the idle speed up a bit.

 

[pat_in_the_hat]

hmm, alright, ill have to try that. Thanks!