Plugs carbon up quickly

A little background first... I've been restoring a 76 KZ900 the past year. The bike had an extended arm when I got it with a two position Pingle fuel valve and filter (no reserve) so the PO may have been racing it. It's got a Vance and Hines header and pods. What happens is, it will start if I clean the plugs but will be a hard start, might take 5 or 6 minutes to get it smooth enough to keep running. Once it's warm though it will actually run pretty good for ten or fifteen minutes, and then will start to deteriorate, will run progressively rougher and will die on deceleration. I'll put it away and next time I go to start, i can't get even a single pop out of it. When I pull the plugs I'll find them all equally coated with black carbon. After I clean them it will revert to how it was before.. hard to start but once it warms up will run pretty good on all four with crisp throttle response, and slowly deteriorate from there. I haven't checked the jet sizes yet... anyone know what the right size for the setup with the header and pods? But mainly I'd like to hear any ideas on what's going on with the plugs. Any suggestions would be appreciated. Thanks

Firstly you need to determine which carbs you have on it, vm26 is stock for an a4. Stock pilot in those is 17.5. Stock main is 115.
"If" it has been raced it may have bigger or different carbs altogether. Also check which plugs you have and post the answers other wise we are all just guessing.
Could be plugs are too cool or jets/carbs are too big or mixture screws miles out and thats assuming your compression is good and your valves are sealing or stem seals are good. Generally with pods and a 4 into one 2 up on pilots and 1 up on mains is the start point.
This topic probably needs moving to carbs/engine not electrical.

Pics of plugs first.
Steve

This is after running about ten minutes.

Here are the carbs:

Pilot jets = 17,5 / Main jets 115 / jet needle in the third Slot with stock air box.
Check your jets size and needle Position first.
Check Ignitition Timing and free advancer movement (cleaning and some grease).

Float levels checked using the clear tube method? Looks like leakage around the gaskets.
Steve

If not already done, would also check valve clearances and adjust to specs.

In order to assure desired fat blue sparks, view sparks with new stock NGKB8ES plugs held against the engine head while spinning over the engine.

What's condition of the spark plug wires? Would use stock metal core ( NOT resistor style wires).

Would toss the "R" plugs and install stock NGKB8ES. NOT "R' plugs.

Good Fortune!

Simple answer is that it looks like your fuel mix is too rich and sooting up the plugs which leads to the soot coating creating a short to earth down the porcelain and a failed spark.
Cleaning the plugs removes the soot layer and temporarily removes the short.
It's also possible that it is a result of excessive oil burning ( worn bores/rings) which will have the same fouling effect.
Black exhaust smoke indicates over fueling coupled with a sooty exhaust outlet and blue/grey for oil burning.

Problem is I had a friend who's a self proclaimed expert on carbs go through them. I should have done it myself. It doesn't smoke at all so hoping I get the jets right and the fuel screws and that will be that. I'll let you all know.

The main jets are 120, pilots I can't read.. looks like 20. If needle is in 3rd position with stock airbox, where should it be with pods? Also I should mention that PO was running the Vance and Hines header without a baffle. I've since installed a generic baffle in the header.

120 is too big, 117.5 max I would say. Leave the needle in the middle. Then colourtune it. Colourtune will get your low rev mixture correct and thats where the majority of riding is done.
You might want to think about 1 grade hotter plugs also. Modern fuel is full of shite that needs burning off compared to 70's gear.