Fires on 3 cylinders Carbs?

My 76 900 will run on 1,2,4 and intermitantly on 3
3 will fire on starting fluid and occationly wheen idling or riding. Changed the 29s to my 26s with no change.
Spark on all cylinders. New rings are not seated so compression seems low @95 each :huh: (but tester is also leaking down it wont hold at highest pressure it reads)
Pulls hard but can feel and hear a miss. I have also changed out the coil for 2+3 and switched plug wires over from 2-3 and 3-2 No change. Has smoke which smells rich. can it be too rich on 3 to run, and yes the plug is wet ( i only pulled them after idle and not after riding around the block. First time on the road in 14 years No tabs/insurance
By the way the 29s havent been tuned very much just a bench sync so far Air screws are 1 turn out stock jetting clip position unknown I didnt tear them down.
Thanks in advance

Have you double checked all your valve clearances. After first setup, clearances can change causing strange occurances.

Also, 95 psi is REALLY low. Sounds like valves/rings bad, not just rings not seated yet.

Brand new proper rebuild and compression should be 150+ on all.

GL.

All valve clearances seem fine bench setting was about 007?
Its only run maybe 45 min since rebuild. Im not to confident in the comp. tester. It pulls better than it did 14 years ago LOL even on 3 cylinders It is also 1015 now My previous post about no comp. was dazed and confused(bent valve was found)
now all have same comp. With my luck the bore job that was done was wrong, but measured correct

If not already done, would perform clear-tube test to double-check fuel level in #3 carb float bowl, especially to assure the fuel level isn't too high, which could result in the suspected over-rich mixture.

Good Fortune!

Patton wrote:

If not already done, would perform clear-tube test to double-check fuel level in #3 carb float bowl, especially to assure the fuel level isn't too high, which could result in the suspected over-rich mixture.

Good Fortune!

I would second this

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- also when you cleaned the carbs did you check the choke circuit (and the little hole in the bottom of the float bowl)? Sounds unlikely since it stays on cylinder 3 with 2 different sets of carbs...but you never know... maybe a massive vacuum leak on thosecarb manifolds? that would likely remain with either set of carbs.

Clear tube method was used on both sets of carbs and the manifolds are new last fall

To aid diagnosis, if not already done, could install a brand new spark plug (per factory specs) in #3 cylinder, and test run to determine whether this has any effect toward improving performance, at least for a short time.

If so, how long and how far before the new plug fuel fouls?

There are only three requirements for combustion:
--- Adequate compression;
--- Satisfactory fuel mixture;
--- Healthy properly timed spark.

At idle rpm, what is voltage at ignition coil primary terminal? Look for same as battery voltage measured across battery terminals. Should be 12~13Vdc at both coil and across battery terminals.

At 3000~4000 rpm, what is voltage at ignition coil primary terminal? Look for same as battery voltage measured across battery terminals. Should be 14~15Vdc at both coil and across battery terminals.

These measurements are to assure that required voltage is reaching the coils. Otherwise, spark quality won't be up to snuff.

Good Fortune!