TOPIC:

tore them apart again, swapped back the old float needle and also checked all the floats, #2 was lower than the rest, which all sat pretty much bang on 23mm. i adjusted it and also noticed that #4 was cock-eyed, so straightened, and re adjusted. #2 bowl overflow hose was actually clogged, so whomever suggest not to assume things, yes, bang on. I cleaned it out and slapped them all back together and in. still havent checked float level yet, as Im trying to figure out how to do that without pouring fuel all over the place. 

so now it no longer back fires, via carb or pipe. no longer pukes fuel out the overflow hoses, although a tiny bit of dribble from #2. likely didnt adjust the height up quite enough i guess. 

But now it hard starts, runs a sec, revs up, and dies. it only runs, if i have the throttle cracked and the choke full on as well. so i do seem to be narrowing down issues, but it ran better when it was barfing fuel everywhere sadly. I also sealed the carb mount hose bib? for lack of a better term, put a tiny dab of gasket maker on the rubber covers and re installed. one was leaking previously. 

any thoughts? 

If it runs only with the choke and/or throttle, the idle / low-speed jets may be clogged. These jets have the smallest holes and are the easiest to block with particles in the fuel or with the residue left behind by old fuel.

You will need to remove the jets to clean them thoroughly; spray-type carb cleaner will not get the job done. Ideally you can use a soft bristle from a paint brush to ensure all of the small holes are clear - it's difficult to do this just visually - or you can use a small-diameter brass wire. Do not use a steel wire: steel is harder than brass, and inserting a steel wire into a brass jet can unintentionally change the size/shape of the hole.

I think a clogged jet issue could be masked by the carbs "barfing fuel everywhere". I have an old single-cylinder 4-stroke dual-purpose bike where I think the PO set the float too high. It doesn't expel fuel, but it will not start with the choke on: I can give it a few kicks with a cold engine (on a warm day) with no throttle and no choke and it will just start idling. The spark plug is a lovely tan. 

i agree. i think the previous vacuum leaks were actually helping it run. Ill pop the top and clean the jets. it tracks that it ran well and then not if the dirt or whatever is travelling through the  carbs. itll give me a chance to move float 2 up a hair as well. 

cheers