jetting \"standard\" kz 1200

I do have a z900 bored to 1200cc (wiseco 10.25:1) Does have 0.395 webcams, 4 into 2 exhaust medium baffled, stock pipes, stock 26mm Z900-A4 carbs and stock intake. Dyna S ignition retarded 3 degrees...
Carb needle has been risen 1 clip and main jet is 130.
And it is still knocking/pinging. .:evil:
This occurs when throttle is approx half up to full applied. Of course when doing this fast...
I was wondering if someone knows what to do about jetting/needles adjustment etc.
Besides of this knocking problems it runs very well and fast (up to 11.000 according to tach)

martijn

I suspect that the bike is rich on top... it is HARD to tell the difference between too rich and too lean... both behave pretty much as described...

To test, take it out and open up the throttle to where the bike is "knocking/pinging" and open the choke a bit... this extra gas will richen the mixture. If the problem gets worse, the main jets you have are too big, as I suspect. If the problem gets better, you need bigger main jets.

I suspect your main jets are the culprit in this problem.

I will definitly try that!! I always thought that pinging was caused by running to lean.
The pinging only happens if the engine has to "pull" starting at approx 5500rpm. If gently it is not noticable.
Thanks George!

Well, if it is indeed "pinging" (which is not the way I first read your note), then you should try some higher octane gas OR try finding a Dyna II with adjustable advance curves... just retarding your advance 3 degrees may not be the best way to retard the advance. You have just come on full advance at 5500 rpm so maybe you are not really retarded there at all based on other things... like if you have newish cam chain components (like the chain). In other words, you may not be retarding as much as you think...

mmm, well indeed all cam components are new. I was struggeling with the camchaintensioner.
The petrol I'm using is the Shell V-power ore similair. This feul has an octanenumber of 98 up to 100.
i read on a similair topic about the air screws (still standard 17,5 jet. Is this airscrew position "controlling"the overall feul-air mixture??

Again thanks for the info George!!

98-100 octane? I guess you are not in the US? If you are outside the US, I am not sure what your octane scale means compared to the US system... Here we have three grades 87-90-93 (at least in Texas... it varies a bit by state/region). The 87 Octane is regular and works well with stock KZ900 or KZ1000 compression.

The airscrew, on the side of the carb body, adjust air that mixes with fuel in the pilot system... While the pilot air/fuel mixture flows throughout the range of operation, it isn't noticeable since the volume of air:fuel mixture at higher rpms (controlled by main jet or jet needle) is relatively greater than the pilot circuit. In other words, if you are mis-adjusted, once you roll off idle, it won't matter much. Your air screws are not fussy and should be 1 3/8 tuns out from lightly seated.

I suspect timing unless the Shell gas you are using has too-low octane.

I do live in Europe, the Netherlands. That feul can be compared to yours! It is the highest ocatane number we can get. Normal in Europe is 93- 95- 98. This because of the high specific Hp per litre and high compressions (not calculated ones but real) lean burn engines...

to be continued

Swopt carbs yesterday. Went from the 26mm kZ900-A4 to the standard 28mm KZ900-B.
I found that the needle is more tappered (1,5 degree more) and the needle tube is 0,05mm bigger.
Put a 120 main jet in it and needle on the fifth.
No more pinging:woohoo: :woohoo:
She stumbles a bit from 4500 to 7000rpm. But then it's a rocket... breaking trough the clutch sometimes and pulling hard from 8 to 10.
So I probably have to lower the needles.
To be continued