KZ750 cleaned carb, compression, spark, no run

I've got an '83 KZ750, I've been lurking around the forums and trying advice in other topics but I figured it was time to start my own. Picked the bike up not running but complete. Pulled and cleaned the carbs. Reinstalled. Fresh battery fully charged. Fresh plugs, all four gapped and installed. Each sparking strong and tested. Go to start (pull in clutch, bike in neutral, full choke, press start). Starter runs and churns no dice. Fuel in the line, in the carbs (pulled them after this to verify assembled correctly) and in channel leading to engine block. Reinstalled, using starter fluid shot a few sprays in to each carb as best I could. Bike ROARS up to 6k RPM for a few seconds before dying again. Won't fire without starter fluid and won't stay running after it fires.

Air-Fuel mixture screws at 2.5 turns for each carb and carbs are sync'd, verified pilot circuit is clear of obstructions. I'm at a bit of a loss as to what I need to try next to get the bike running. Any help would be appreciated.

Are you using the stock air box and oem style filter element?

your carbs are still dirty.

Yes, stock airbox and filter element. I was (and still am) skeptical about having to hook the airbox just to get the bike to fire, but after some hair pulling I caved and hooked them back up to the same result (dead air should be the same whether the bike is sucking from the airbox or from the garage).

If the carbs are still dirty then I'll be damned. Twice cleaned so far and there aren't nearly as many channels as there are on my Vulcan 750. Is there a guide for cleaning?

Another place to look is for a vacuum leak - starting fluid will run the engine to higher RPMs, but that sounds to me like you've got something set up wrong in the carbs and it's just too lean.

I'll back the air/fuel mixture screw out a turn or two more to verify. If that's the case I can at least work from there.

So, backing out the screws to about 3.5 turns and a quick spray of starter fluid choke all the way out the bike starts and runs for a bit at about 6k (pushing the choke back in drops the RPMs to about 3k before shortly dying) I can try taking the screws out to 4 turns but at this point it would seem the jetting is all wrong in these carbs. I'll pull the carbs again and verify the pilot jets are the right size, otherwise I'm not sure what this would be.

Just putting in my .02. I've done this too many times recently too. Are all the vacuum hoses in place? Ends split and make vacuum leaks.

Running the bike with the airbox and filter definitely matters compared to open, non-restricted carbs. Along with the proper restriction created by the filter there is the affect that all 4 carbs have on vacuum inside the common airbox vs sucking through open air. You were smart to eliminate that variable despite the effort required.

By any chance do your carb holders have vacuum ports on them? If so, make sure they are capped. Ed

marcoceppi wrote: ...carbs... Twice cleaned so far... Is there a guide for cleaning?

Good Fortune!