Pilot Jet question

I have a 1978 KZ1000 with a 4 into 1 Kerker, Pods, VS28 carbs, dyna coils. I have not yet installed the dyna s elec ignition yet. It has 120 mains, needle jet set on the 3rd clip, floats set ok, exhaust gaskets good but still some popping at decelleration and a little just idling. From reading some of the posts I am only guessing maybe to go up on the pilot. I dont now what is currently in there. I think stock is 15 so I figured if it is 15 try a 17.5 ??? How do you know what size you have? The carbs have been cleaned and in good shape throughout. Carb boots, clamps exhaust gaskets are in good shape. I wanted to try the pilots first and also Wiredgeorge's coil mod but don;t know how to determine pilot size. The bike runs great otherwise.
Any help would be greatly appreciated. The bike is ridden very often or as much as I can.
Thanks!

Its usally stamped on them, but you will probally need a magnifying glass to see the numbers, unless you got alot better eyes then me

1045

I suspect you might want to figure out what carburetors you have before trying to rejet as rejetting is relative to the original jetting. Since VM28 carburetors didn't come on any 1978 bike except the Z1R, you most likely have carburetors from some other model and jetting varies a great deal from one assembly to the other.

I went to Z1enterprizes carb reference guide and they match the 28's. They have a flat top with 2 phillips screws. It looks like the later version. Z1 says there were an earlier and later version 28's.
Hope this helps.
Thanks

The two-screw tops are Z1 VM28SC... the 73/74 had the same jetting while the jetting changed a lot in 75 for the Z1B. The early 73/74 carbs had 17mm drain plugs in the bowl bottom while the 75 had more normal 6mm screws angled off the side of the bowl. Which does yours have?

Mine are the 6mm angled off to the side of the bowls.

The carbs described are the Z1B version; #112.5 main jets 5J9-2 jet needles and #17.5 pilot jets, stock set up. Your main jet and jet needle set up seem correct. Usually the 1.5 slide cut out and #17.5 pilot jets will accomodate the use of pods without bumping up the pilot jet size. The backfiring you describe may be from poor combustion as opposed to incorrect jetting. Before messing with the jetting, go to our website and check out two of the tech tips under "wg's Tech Stuff Index". Once is labeled VALVE CLEARANCES and the other COIL REPOWERING. Either tech tips describe fixes for problems that can cause incomplete combustion and the backfiring you describe. Both issue should be checked by any vintage bike owner before messing with the carburetors.

I will do that and post what I find. Thank you all for your input.