Kz1000 Jetting

I have a 1977 KZ1000 B1 that has been heavily modified. I am looking for suggested jetting for my VM26SS carbs. When I rebuilt the bike I replaced the main jets with 122.5's and raised the needle 1 notch. The bike runs smoothly from idle to WOT, but is too rich...plugs are black and sooty.

The engine has the following mods.

Heads Flowed & Polished (PO so I don't know exactly what was done)
Air box replaced with Pods
Hindle 4-1 Header
Supertrapp 4" Can with 10 spacers
Dyna S electronic ignition (stock coils & wires)

Thanks,

Post edited by: Batman, at: 2007/10/10 16:49

Post edited by: Batman, at: 2007/10/11 16:31

Another pic...

Sooty plugs and backfiring? This is incomplete combustion... while it MIGHT be caused by incorrect jetting, it is just as likely it is caused by something else. On our website (see my sig) are two articles you should look at... under "wg's Tech Stuff Index". One is Valve Clearances and the other is Coil Repowering. Either of these articles might cure the plug fouling. If they don't you will need to figure out WHICH VM26 assembly you have in order to rejet. The main jets you are using are far too large for ANY of the about 6-8 different assemblies that were installed on various KZ900 and KZ1000 models. The jetting you need will be relative to the specific assembly. The assembly you have has an ID mark stamped on the flange where the flange inserts into the carb holding bracket. Look just UNDER your choke arm... there will be five numbers and letters stamped on two lines and they are hard to read as they are shallow and small. Figure out which carb assembly you have and I can get you close on the jetting.

Thanks wiredgeorge,

I have been on your site and read both articles. I was hoping that the jets were the issue so I am exploring that first. When I roll on the throttle, the engine makes its customary snarl till approx 1/2 - 5/8 throttle, then the sound changes...sounds muted/wet.

I am not getting any backfiring, some popping and snapping from the exhaust when off the throttle/decelerating and also occasional popping through the intake (mostly when engine is cold)...valve clearance perhaps?

I think the ID from my carb is 101 7A...you were right, very hard to read.

The issues noted in the tech articles should be undertaken before trying to correct performance issues by rejetting... In any case, your carburetors are from a 77 LTD (KZ1000B1).

Stock: 105 mains, 5DL31-3 jet needle, 15 pilot and 0-5 needle jet.


With pods and the 4 into 1 start at #115 mains, leave the jet needle along and try some 17.5 pilot jets.

To be honest, I don't see as many of the LTD carbs as I do the standards... The KZ1000A1 has a different jet needle/needle jet combo and I would recommend #20 pilot jets and reclipping the 5CN8 jet needles to the 4th slot. The 5DL31 jet needles are a tad richer than the 5CN8 but the 0-5 needle jet is a tad smaller... You don't need to go bigger on the mains but you may want to pick up a set of #20 pilot jets in the event my jetting guess isn't spot on.

George,

I pulled the carbs and I had 122.5 mains and 15 pilots. I ordered 112.5, 115 & 117.5 mains, 17.5 & 20 pilots. Since the carbs are off I am also going to check the valve clearances.

Just so I am clear...to start, 115 main, reclip needle to 3rd position and 17.5 pilot.

Thanks for your help!

Post edited by: Batman, at: 2007/10/11 16:35

Agree with everything George said and I would also drop the needles back to the 3rd Groove.

Post edited by: larrycavan, at: 2007/10/13 06:47

Thanks all,

I am heading out of town for the weekend, but will rejet when I get back...15 main, reclip needle to 3rd position and 17.5 pilot. I am also going to check the float level and bench sync them before they go back on the bike.

As there are only a few weeks of riding left here, I am going to leave the coil rewire and valve's for my winter maintenance...the bike is getting completely stripped for an engine clean and polish, frame repaint, new electrical covers and new wiring.

Batman wrote:

...also going to check the float level and bench sync them before they go back on the bike....

With the carbs reassembled and upright level on the bench, recommend the clear plastic tube test for reading float level, and do NOT rely on the upside-down dry bowl-off physical measurement method.

The wet clear plastic tube method is more accurate because it shows the true actual service fuel level.

Good Luck!

Patton wrote:

The wet clear plastic tube method is more accurate because it shows the true actual service fuel level.

That's the method I'll use...

Thanks

Post edited by: Batman, at: 2007/10/13 12:17