Jetting for stock airbox??

If I go back to a stock airbox from pods, what kind of jetting changes will I need to make? Any Ideas? You still checking in George?

What bike are you talking about? Helps to put your bike info in your signature line so people know what you're asking about...

Sorry, 1978 kz1000, but it has 76 vm carbs off a kz900

Pro_window78 wrote:

If I go back to a stock airbox from pods, what kind of jetting changes will I need to make? Any Ideas?....

What exhaust system is fitted?
Are existing jet sizes known?
Are carbs stock oem for 1978 KZ1000?
How do sparkplugs appear now (color)?
With existing setup, what is plug reading after high speed throttle chop test?

Would suggest leaving the existing jets in place until test running with airbox installed, and equipped with a K&N filter. The K&N flows as well or almost as well as pods. Might be pleasantly surprised with acceptable performance from exiting jets, and at least have some basis for comparison.

A critical factor in main jet sizing is the plug reading at full throttle (readily determined by high speed throttle chop test). Tan and clean would be nice.

A critical factor in pilot jet sizing is a nice regular steady low rpm idle with strong pull away from idle and no bogging or surging or excessive exhaust popping at lower throttle operation, just nice even lower rpm cruising.

All this presupposes the other engine components being up to snuff -- compression, valve clearances, correctly timed quality spark, ample clean fuel supply, proper floatbowl fuel levels, and that carbs are clean and otherwise okay internally.

Important to remember that even perfect carbs can't compensate for deficiencies in the other components.

kawasaki.com diagram shows 17.5 pilot and 107.5 main.

This 1978 KZ1000 carb rebuild kit from Z1E includes 2 different sized pilot jets and 2 different sized main jets. Click here > Carb Rebuild Kit

Z1E also lists pilot jets separately in sizes 15, 17.5, 20, and 22.

Good Luck!

Here's info from Z1E as to 1976 KZ900 carbs.

26mm (VM26SS) KZ900A4 & A5
Main Jet 115
Air Jet 1.0
Needle Jet O-6
Jet Needle 5DL31-3 (last number is clip position)
Throttle valve (slide) 1.5mm cutaway
Pilot Jet 17.5
Air Screw setting 1 3/8 turns out

Z1E's KZ900 carb rebuild kit shows a singe pilot jet and a single main jet, presumeably 115 and 17.5; and also shows same 4 different size separately available pilot jets.

The KZ900 carbs are very forgiving and user friendly carbs, which may perform similarly on the bike at hand even after replacing the pods with a stock airbox and K&N filter.

Am well satisfied with performance of the oem Mikuni 26mm carbs on my KZ900-B1 kitted to 1015 with K&N filter in stock airbox and 4>1 Kerker.

Good Luck!

They were just rebuilt and custom jetted by George. It has a Kerker megaphone and my plugs are sooty, I am putting new coils and wires on, just ordered from z1. It has a dyna 3 ignition. My old original coils were cracked and suspect so I went ahead and got new stuff. I just prefer an airbox, It's how the bike was built for a reason. Just my .02 tho. I have also done the coil repowering mod. Is that hard on the coils? would it cause the oldies to go out? Just rambling now, sorry.

Pro_window78 wrote:

They were just rebuilt and custom jetted by George. It has a Kerker megaphone and my plugs are sooty, I am putting new coils and wires on, just ordered from z1. It has a dyna 3 ignition. My old original coils were cracked and suspect so I went ahead and got new stuff. I just prefer an airbox, It's how the bike was built for a reason. Just my .02 tho. I have also done the coil repowering mod. Is that hard on the coils? would it cause the oldies to go out? Just rambling now, sorry.

Coil repowering mod is NOT hard on the coils, and simply helps assure getting full battery voltage to the coils like they're supposed to have anyway.

And the coil mod should not damage an older coil.

Take care when installing the new green Dyna coils to avoid the primary terminal screw head from touching and shorting out against the spacer on the coil mounting bolt. It's a close fit in that area. Can insulate the spacer with shrink wrap, or zip ties, or whatever, and might perhaps use a plastic spacer instead of the oem metal spacer.

Good Luck!

Sooty plug condition may be partially resolved with the new Dyna green coils and Dyna plug wires, all toward improved spark quality.

Won't hurt to also check proper functioning of the advancer unit and assure it's clean and freshly lubed with moly grease.

Would also assure valve clearances being to specs, as too tight valves can cause loss of compression at normal engine operating temperature which in turn results in sooty plugs.

Good Luck!

I went with 17.5 pilots and 110 mains and couldn't be happier. It is a stock '78 KZ1000 A2 with stock airbox and filter and Kerker 4-1 with street baffle.

Yeah, I'll be ordering my shim kit within the next couple of weeks.

Gman wrote:

I went with 17.5 pilots and 110 mains and couldn't be happier. It is a stock '78 KZ1000 A2 with stock airbox and filter and Kerker 4-1 with street baffle.

Say GMAN do you know what clip position your needle is in and how many turns out on the pilot screws?

I just bought the same bike and it appears to be having some carb issues.