Misfire and popping on deceleration

[226dark]

I had my new tires put on along with spokes trued and while at i I thought I'd have my trusted mechanic sync the carbs after my bench sync.
It runs worse! It misses occasionally at idle, it is perfect while accelerating and steady throttle, then let up on throttle it pops and misses badly to the point of being embarrasing even riding to the nearest stop sign intersection. At speed and slowing down it's real bad. Not sure yet except that if you want something done right on your bike do it yourself! Is it the carb balancing done wrong or something else that got messed up?

Also it is is only the right side.
I am convinced that this reputable experienced mechanic of many years did not do the work himself, but rather had a younger new guy do the work. Spring is extremely busy for him and I had to wait an entire week to get the tires and tubes on.

 

[HoughMade]

Sounds lean. Open up the idle mixture screws a turn and see what happens....or look for an air leak.

 

[226dark]

Sounds lean. Open up the idle mixture screws a turn and see what happens....or look for an air leak.

Interesting that you mention air leak and was pondering on that before.
When i first got it running (and unlicensed, unisured) I took it out for 3 quick .25 mile rides up and down the block. The 2nd run it had this same symptom and what i was using to cap off the right intake boot - thread protector rubber thing from hardware store - went missing and third run replaced it and good again.
Currently though, I have the actual OEM blind plug on that barb.
I did in fact turn out the idle air adjust for right side 1/2 turn and same.
WHAT DID THEY DO TO MY RIDE?
(no time today to mess with it but will look again for air somewhere)

 

[faber]

If it's consistently on deceleration you should also look for exhaust leaks.

 

[226dark]

I should have updated this sooner. The problem started when I got it back from the mechanic who i asked to sync the carbs along with new tires on, tubes, spokes tightened.
I thought the exhaust leak suggestion was great and even went so far as buying a new header gasket to crush in. Not the problem.
I tried swapping around the left and right spark plugs. The same.
I tested the coil and good. While at it cleaned the bullet connectors again.
Close to 500 miles on rebuild (over 700 now) I checked the valve clearances. 3 were within spec (intake .003 - .005 in) (exhaust .006 - .008 in). I adjusted all of them to the lower tolerance. It just happened that the right exhaust was at .009 and not an easy slip-fit .009 but I couldn't wait to start it up after adjusting it to .006. Nope, was not the problem either.
Then with a timing light on the right H.T. and at idle with the light skipping a beat occasionally, I started moving around the ign. coil and condensor wires and then the timing light just stopped and it made an effort to run on one cylinder then died. On closer look one of the slide connectors going into the 2-prong condensor connector was not clicked all the way in. It was still plenty in and the bike ran perfect opening the throttle and at steady throttle, but then the misfire & popping on decelerating and occ. at idle. The mechanic may have pulled it accidentally or it may have worked loose on the 40 mile ride there but it only started doing that after I got the bike back. IT IS a very old bike, so stuff happens.
Now if any question, why did it never once miss when holding the throttle open ? I can take a guess - higher voltage or faster breaking of the points but not sure.

 

[drewpy]

the revs would mask the missing cylinder and poss the 'lectric would jump the gap.