720 gas pop and miss??

Just got the 720 gas Standard running that has no starter -used my 620 and a endless belt on the pulleys to start the 720
-have rebuilt the carb and all ports appeared to be clean and open
-tractor starts real good and runs OK --but at idle there is a POP and miss while running-
-I installed spark testers on both plug wires, but it is hard to tell a skip when the miss and pop happen
I suspected electrical -switched one at a time, spark plugs, cap, rotor, condenser from other 720 gas in shop that runs good -removed points and filed square on vise
Nothing changed electrical helped at all
I suppose it is the carb that is still not clean
I will remove and re-clean the carb
could it be the valves not closing correctly?
could it be the distributor itself? compared to the other 720 gas tractors I have, the distributor is installed in a completely different orientation - I was going to remove the distributor, check the weights and retime the distributor
-had it running and closed both idle screws -it stopped popping but the tractor did not stop -possibly idle circuit still plugged and gas being pulled from the load circuit??
when you apply choke it does seem to run better- therefore carb issue--
Any help appreciated
Ken

I think you may be on to it being a carb issue but do remember a guy that had an AOS that acted the same way....finally found that a weak valve spring was allowing a valve to open and leaning out that cyl. Without pulling and testing the springs I am not sure how you would prove it...Vaccum Gauge?
Will you be changing your handle come Sept?

Yes Bob - maybe Formerly Canadian Ken---
But I do prefer Aussie Ken -what do you think?

I think I will invetigate the valve issue first, then the carb again - to rule out the carb, I should just switch the carb from one of the 720"s that runs good to rule that out -there are luxuries in having duplicates of the same model at home!!!
Ken

You will have to learn to post with an Aussie accent LOL. Good luck with the 720.

I had something similar going with my JD 630 and it was caused by the carb. I would make sure I had a good stream of gas coming out at the carb first and then put in the working carb from you other tractor. You could also put your carb on the working tractor and see what happens there. Either way I would start with the simplest solution and work to the most complex/expensive solution which experience has taught me is the best methodology for old two cylinders. Have you checked your air cleaner bowl? Found one of mine full of water and gunk one time which will also cause similar issues. Has to be one of three issues: not getting proper spark, air, and/or fuel. Good luck Aussie Ken.