First, here's a pic of the suspected problem:
All four pickup tubes are like this
I've been beating my head against the wall trying to get the fueling right after installing a set of pistons and barrels from an 850 and a Vance & Hines 4-1 exhaust.
All of the adjustments I've made have produced results that are inconsistent and I suspect the cracked choke pickup tubes may be letting unmetered fuel into the air/fuel mixture.
Plug chops show that the 1 and 4 cylinders are fouling the plugs and they are often wet, while 2 and 3 are lean. Adjustment of the air and fuel screws has little to no effect on this.
The carbs have been fully disassembled and soaked in carb dip, had all passages sprayed out with brake cleaner and reassembled with fresh o-rings.
I'm currently running the stock air box with K&N air filter, fresh air box boots and fresh intake o-rings.
The carburetors have 112.5 mains, pilot jets are stock and the needles are set with the clips in the center position. All parts are OEM, not from aftermarket rebuild kits. Float height is set at 25mm and the float needles all move freely.
The bike will usually run fine on initial start up, but the 1 & 4 cylinders stop firing as the plugs become fouled, with occasional surging when they happen to fire. I have confirmed that 1 and 4 are receiving good spark by placing a clean spark plug in the boot for 1 or 4 and holding it against the motor while pressing the start button.
So, could the split choke pickups be the cause of all this? If so, can they be removed and replaced? I can't seem to find them for sale, unless I'm using the wrong search terms.
Any thoughts or advice would be greatly appreciated.