TOPIC:

I got a PM from a member and thought it worth sharing.

bike is running extremely rich black smoke, at idle, rev's take a while to settle to idle, intermittent pops from the exhaust and it drinks fuel. in short I've had carb solvent through every orifice in the bare carb bodies , compressed air, they've been to the professional ultrasonic cleaner twice, even bought myself 1! to make sure!!! they seem to be as clean as a whistle, I've disconnected the choke mechanism to be sure they're sealing OK. and bottomed out the pilot screws but still it runs rich, in short how can i be sure there's enough air getting through the pilot circuit without drilling out the brass plugs to check!! and clean them mechanically,, they appear to be clear when I'm running air and solvent through them but that's under pressure !!!! I seem to have hit a brick wall....( any advice would be greatly appreciated,

FIRST : Don't drill ANYTHING ! (Desperation can make us do silly things!)

Taking everything as stated at face-value your problem leaves me somewhat mystified, too ! Is this Rich problem all 6 cyl's? I'm going to have to pick my own brain for a for a while, but wanted to Acknowledge your inquiry and put it in the forum for others to take a poke at. I'll be back !

If it's running very rich despite the mixture screws screwed right down, then it must logically be getting fuel from somewhere. The only thing I can think of is your float levels must be set way too high. Or the float valves are kaput.

Usually, if an engine is running so rich that it's billowing black smoke, it's on the verge of stalling out from being over rich. IF the problem is associated with high float levels, you can see this by looking in the carb bores when running and SEE gas burbling up around the main jet. So look for this first.

I wouldn't discount the choke plungers. If they aren't closing and are sitting just barely open for whatever reason, this could be your issue.

At this point I wouldn't be looking at the anti backfiring valves on the left side of the carbs. You're running rich right now and that will cause the backfiring even if the antibackfiring valves are working.

The issue with the idle ramping down slow is attributed to the throttle plates being open too much and the idle is actually being achieved with the transition ports and partially the main circuit. What happens here is the main circuit is feeding the fuel that the idle circuit should be feeding and it really takes a significant drop in carb bore air flow to stop the feed of fuel from the main circuit. The way you're set up now is causing just enough air flow to keep fuel moving through the main jet. The only way you could have set up the carbs to achieve idle and have this happen is when the idle circuit including the transition ports are partially plugged. NOTE HERE the transition ports are the smallest point in the idle circuit and if I learned anything here on this site it's a valuable lesson from Scotch to blow clear the transition ports from the port back through the carb with the idle jets removed. I've rebuilt over 500 carbs in my career days as a Chrysler mechanic and I can say that the Holley 2 barrels gave me trouble ALL the time with transition ports. I wished Scotch had taught carb rebuilding back then. Scotch's flushing tool with usage instructions is without a doubt probably the best $$ you could spend to sort out the majority of the issues with the KZ1300 carbs. The only thing it doesn't sort out is the initial set up of the throttle plates and air bleeds. That is just following the proper instructions and not taking any short cuts.

KB

This may be too simplistic, but have you checked air box, filter and inlet tracts?

Some helpful ideas, for sure. Thanks for helping out, guys !

Some additional ideas due to lack of more specific info.

Was this bike running prior to the carb-work/mods being done? What prompted the work? It was noted in the inquiry that some parts were changed out: <."....coils/leads, plugs, electronic saches ignition, jet kit (standard) ....."> Anything specific or simply upgrading and due-diligence in being thorough! Not clear about the "electronic saches ignition"

When the jetting was re-placed did the kit come with float needle-valves? Which cyls. are being affected by the RICH syndrome? All 6? Given the recent work; If all 6 are RICH then it's likely there's an "Assembly" issue. If the problem is (example) with cyl's #1 & #2 only, we can focus on one carb. If the problem (example) is with cyl's #1, #4 & #5 we know it's an issue with those venturi's and related circuits in 3 carbs. Were the carbs "statically" sync'd on bench before installation? (Strip of paper trick?)
Nothing mentioned about "flooding". Are the Nytrophil floats still floating? (correctly) Buoyancy is critical. If they're absorbing fuel, "RICH" is guarantee! With carbs off the bike and connected to a temporary fuel supply what do the levels do over a couple of days. If the floats are absorbing fuel, the carbs will over-flow.
Not to offend, BUT: 1) Make certain all idle-jets are screwed in snug. It could be easy to drop them in during re-assembly but forget to actually seat several of them prior to installing the idle tower caps.. (Murphy's Law !) 2) Same premise with the Enrichment-valve assembly - It is difficult to imagine but if a diaphragm-spring is left out that carb will be RICH.These last two ideas are a real "stretch of the imagination but at this point......? (refer to Mr. Murphy) With clean and unobstructed parts, there is NO likelihood the piston assembly is jammed closed as the diaphragm spring is quite strong relatively speaking and the piston-valve will be pushed (IN). If for example the spring was forgotten the slightest vacuum would actuate the diaphragm, closing off the air supply port (supplied from under the main-jet diaphragm immediately behind the enrichment valve) and this will cause RICH.
It was indicated that the Choke assembly was disconnected to ensure the plungers are closing. I will presume that the disconnect method was by simply loosening the securing screw on each of the 3 choke lifting yokes, allowing the plungers to remain closed regardless of the choke-lever position? Check the choke plungers again with a loupe or magnifying glass. TINY slivers of aluminum/brass from the threads of the body and choke plunger retaining nut can (and will) get imbedded in the seal. Check the "seat" in the bottom of the housing. If there's any nicks, pitting etc., the choke(s) will leak. Note: When the lifting yokes are secured with their screw it's important to ensure the only contact between the yoke and spool is at the flange on spool end. If the yoke is slightly off to one side and touching the spool, it is possible for the slight side-pressure to cause the plunger to bind and not return to full-closed.
Something that I think is easily over looked - Ensure that the fast-idle cam/roller are not in contact at IDLE with the choke fully OFF! This can play havoc with sync'ing and not getting a quick return to idle. I have reason to believe that this point being misunderstood/overlooked can result in attempted compensations elsewhere and could exacerbate a RICH condition. Kawboy mentions this very condition which points back to an inadequate STATIC sync and possibly an incorrectly adjusted Fast-Idle set-up.

OR, maybe you fuelled the tank with your "40/1:woohoo: " weed-eater fuel ....... ?
Hope something within these ideas "Turns ON the light-Bulb" !!