76 kz900 low rpm issue

The jet needle and its clip position has little effect during first 1/4 throttle position, and mostly affects performance between 1/4 ~ 3/4 throttle position.

I would not suspect the jet needle clip position to be causing hesitation or stumble upon initial pulling away from idle, as performance in this lower rpm range is still being primarily governed by the pilot circuit.

Good Luck!

Running strong in mid-range indicates that the jet needle clip position is just fine.

Good Luck!

Sorry but i cannot explain myself good enough because of my bad english.

When i say "turning out the pilot screw" i mean the screw placed on the bottom of the float bowl engine side.

Turning out that screw i can notice some improvement.

carbs installed are from a 77kz1000, so without the air/fuel adjusting screw side placed.

Will post other news!

Thanks a lot

vict182 wrote:

Sorry but i cannot explain myself good enough because of my bad english.

When i say "turning out the pilot screw" i mean the screw placed on the bottom of the float bowl engine side.

Turning out that screw i can notice some improvement.

carbs installed are from a 77kz1000, so without the air/fuel adjusting screw side placed.

Will post other news!

Thanks a lot

Yes, a bottom-located pilot adjusting screw regulates volume of air/fuel mixture allowed from the pilot circuit into the carb bore and is often referred to as a "pilot mixture adjustment screw." Turning counter-clockwise richens by allowing additional air/fuel mixture. Turning clockwise leans by allowing less air/fuel mixture.

Whereas, a side-located pilot adjusting screw regulates only volume of air allowed to the pilot jet which affects air/fuel mixture allowed from the pilot circuit into the carb bore and is often referred to as a "pilot air adjustment screw." Turning counter-clockwise leans by allowing additional air into the pilot circuit.

Summary ---
Side-located pilot screw turns out counter-clockwise for leaner and turns in clockwise for richer.
Bottom-located pilot screw turns out counter-clockwise for richer and turns in clockwise for leaner.

Noticing improvement by turning out the bottom-located screw results from enrichening the pilot circuit. Perhaps slight choke application would produse similar improvement.

Side-located or bottom-located pilot adjustment screw influences the pilot circuit which primarily affects idle and lower rpm performance during the first one-fourth opening of throttle posuition.

As earlier noted, the jet needle clip position primarily affects one-fourth to three-fourths throttle opening position, and imo the clip position would have very little influence on any hesitation or stumble when first pulling away from idle.

Good Luck!

That was just awesome!

Thanks a lot!!!

Now i have a lot of notions so i can proceed with my job!

I'll keep you adviced.

question:

i had as a notion that less baffled exhaust means more air flowing so you need to richen the mixture.

i had an aftermarket 4in1 which was very quite. i have replaced it with a kz1000j 4in2 and it's where the issue begins. seems i'm running lean.

could it be that the old aftermarket 4in1 allows more air than the actual kz1000j 4in2?

this could be the only reason of my problem.

or my notions about that are wrong?

You switched from stock air filter element to a K&N which probably (? check to verify) flows more air than the stock element. That will 'lean out' the air/fuel mixture requiring possibly a pilot jet change, a jet needle raising (drop the needle clip 1 notch), and a bigger main jet. *Possibly.* Depends on how much extra air the K&N flows.

When you mess with the intake side, always a chance of dirt getting inside the carbs, and --- as chance would have it -- the pilot jet circuit has *very* small passageways, they're very easy to get blocked, and could explain the poor acceleration off-idle.

Put it this way. If you have returned to the prior condition, ie. stock air filter element *and* the 4-into-1 that you had before the hesitation, and IT'S STILL NOT RIGHT, and by your posts that sounds like it is in fact where you are going -- then make sure to return the pilot mixture screws you've been adjusting *back to where they were.*

If you still have the hesitation after going back to the original airbox and 4-into-1 and pilot setting -- you may well have some dirt now in the carbs.

Another way the pilot circuit can clog:

1) if you took off the gas tank at any point and, seeing as though it's a 30+ year-old machine, the petcock filter is worn -- sediment in the gas tank that gets sloshed around due to the unusual angles you put the tank in to get it off may flow down the fuel hoses into the carbs.

Did you install or do you have inline fuel filters?

There is usually dirt and sediment in the gas tank, and often dirt and sediment in the bottom of the carb float bowls, and so jostling things around can dirty up the passageways in the carbs. Having an inline fuel filter is cool because it can really cut down on this type of problem, just fyi, and I hope your pilot circuit's not clogged btw. Cheers and good luck!

vict182 wrote:

@Blue: so you still have this problem?

Yes I do. I've been too busy to tackle it. It's not bad enough to worry me but someday I'll pull (ugh!) carbs again and check it out.