76 kz900 low rpm issue

Hi all

Here is my problem

Bought a 76 kz900.
77 kz1000 vm26 carbs, 77 kz1000 stock airbox, 4in1 exhaust.
Everything worked fine, well tuned.

Put a k&n air filter element in the stock airbox, and a kz1000j 4in2 stock exhaust.

Now has little but annoying hesitations at low rmp when i give a little gas, cruising at low rpm. as soon as i give more gas hesitation disappears and runs fine. during this "running fine" in the way to redline, there is less torque than before but well i'm not looking for a race bike so i can stand it. what i can't stand are those hesitations at low rpm with little gas.

Playing with pilot adjustment screw doesn't really help. anyway it seems that turning them out the problem decreases.

How can i fix it?

thanks

i would put the old air filter element back in and see what happens....kind of wierd...you went from 4-1 to a stock system but also switched from stock paper filter to k/n....
apparently that bike is way more sensitive on the intake side....my waguess is that if you put stock air filter back in and its better, if you want to run k/n, go up 1 size on pilot.....hope this helps.....

I second the going up one size on the pilots. Roy

Got low voltage to the coils? Got enough amperage there? Try running a good wire from the batt. to the coils and take it for a ride.

Ok will give a try to your suggests, and i'll keep you adviced.

thanks a lot!

vict182 wrote:

Hi all

Here is my problem

Bought a 76 kz900.
77 kz1000 vm26 carbs, 77 kz1000 stock airbox, 4in1 exhaust.
Everything worked fine, well tuned.

Put a k&n air filter element in the stock airbox, and a kz1000j 4in2 stock exhaust.

Now has little but annoying hesitations at low rmp when i give a little gas, cruising at low rpm. as soon as i give more gas hesitation disappears and runs fine. during this "running fine" in the way to redline, there is less torque than before but well i'm not looking for a race bike so i can stand it. what i can't stand are those hesitations at low rpm with little gas.

Playing with pilot adjustment screw doesn't really help. anyway it seems that turning them out the problem decreases.

How can i fix it?

thanks

When I had that problem, the biggest "fix" for it was to raise the carb needles a slot or even 1/2 slot.

The pilot jets did improve it a little but not enough to cure it. Needle position was dead on it, one slot makes a huge difference in off idle throttle response.

i second raising the needle your a bit lean in the transition area between the pilot and the midrange i'd try one clip position to begin with my self

i had the same symtoms when i put a 716 big bore kit on my z650,(pod filters) went up on the pilot jets and this cured the problem

Intake side changes have a dramatic effect. The advise here already will get you going fine.

Up 1 on pilot, and lower needle clip position (raise needle) to richen off idle to almost 3/4 throttle.

If your anxious to ride, the main can be tuned later with your butt-dyno!

Good luck.

vict182 wrote:

during this "running fine" in the way to redline, there is less torque than before but well i'm not looking for a race bike so i can stand it.

thanks

My 650 also went from a Kerker 4-1 to a stock 4-2 exhaust. I also run a K&N in the stock airbox and feel the same thing you do. First of all your going to lose some torque at higher RPMs with stock exhaust. My bike feels softer near redline but pulls much better on the bottom end and at midrange (which is where we ride 90% of the time) I adjusted my floats which were ALL high and noticed a smoother, better responding motor. But still have a slight hesitation at lower R's. I agree with bumping the pilot jets up a size to help with lower RPM response.

@Blue: so you still have this problem?

@all:
don't think it's an electrical problem, as i hadn't had it before to make those changes on the bike.
replaced k&n with stock element, no difference.
while playing with pilot screws noticed some improvement turning them out.

will try to replace the 4in2 with the old 4in1 just to make sure that this issue is caused by this change, before to start playing with jets.

any other suggestion will be great!

vict182 wrote:

...while playing with pilot screws noticed some improvement turning them out....

FWIW, turning side-located pilot screw out counter-clockwise leans out the pilot mixture by introducing more air. Edit -- as later noted, the carbs at hand have bottom-located pilot screws which turn out counter-clockwise for richer and turn in clockwise for leaner.

Clean pilot circuit is critical to lower rpm performance and performance during first 1/4 throttle. And critical to smooth strong pull away from idle without hesitation or stumble.

If not already done, would also check float bowl fuel levels (using the clear tube test method). Edit -- I see this has been done.

Good Luck!