Kz1100 running very rich

well I did get this one running this weekend after doing the carbs and new rear shocks and even got to put a few miles on it to

I'm going to pull the carbs off and rebuild them along with some new carb and airbox boots. Taking off the airbox boots,the boots were very hard.

I went thru the same thing on a kz1000 Checked every thing, Stock jets, float levels right on, New fuel valve even double checked the air intake. in my case it turned out that PO had bored out the main jets way too big. still had the stock jet numbers on them At full throttle it smoked like a diesel and burn your eyes to follow behind it. I guess the PO thought he'd make a wild guess on the jet size. :ohmy:

Barry2 wrote: I went thru the same thing on a kz1000 Checked every thing, Stock jets, float levels right on, New fuel valve even double checked the air intake. in my case it turned out that PO had bored out the main jets way too big. still had the stock jet numbers on them At full throttle it smoked like a diesel and burn your eyes to follow behind it. I guess the PO thought he'd make a wild guess on the jet size. :ohmy:

I was at a local vintage motorcycle shop and the owner told me that they had the proper size bits to drill jets. I said why would you do that with the price of jets? Don't get me wrong I'm as cheap as the next guy but even I never understood doing that. Especially when you pay for drilling the jets is as much as a set of new jets.

If I drilled jets I'd end up being confused about which jet is what. lol

As long as jets are readily available there's no need for drilling unless you're looking for that sweet spot. I'm kinda anal that way. :whistle:
Steve

Perhaps not applicable to the bike at hand, but would check for the following possibility that can happen on Z1 models with the stock air-box configuration.

When there's a crankcase vent tube that exits into the air-box, presence of raw gasoline in the carb throat (from whatever reason) may flow backward toward and into the air-box.

Raw gasoline that gets inside the air-box would intuitively be expected to escape via a drain hole, likely through a hose attached to the drain hole which allows the raw gasoline to exit onto the road surface or garage floor or wherever.

BUT, raw gasoline that gets inside the air-box -- instead of discharging via a drain -- might flow down the crankcase vent tube directly into the crankcase. Which is a possibility with the Z1 air-box design.







Long story short -- do what's necessary to assure there's no gasoline draining from the air box down through the crankcase vent hose into the crankcase.

Carbs with a functioning overflow circuit usually avoid raw gasoline in the carb throat because the maximum float bowl fuel level is governed by height of the overflow tube in the float bowl.

However, when using carbs without an overflow circuit (such as the popular Mikuni smoothbores) -- or any carbs with a non-functional overflow circuit -- a leaking fuel valve (or other cause) may result in raw gasoline rising from inside the float bowl up into the carb throat.

Good Fortune!

Good point.
Steve

76KZ900 wrote:

Barry2 wrote: I went thru the same thing on a kz1000 Checked every thing, Stock jets, float levels right on, New fuel valve even double checked the air intake. in my case it turned out that PO had bored out the main jets way too big. still had the stock jet numbers on them At full throttle it smoked like a diesel and burn your eyes to follow behind it. I guess the PO thought he'd make a wild guess on the jet size. :ohmy:

I was at a local vintage motorcycle shop and the owner told me that they had the proper size bits to drill jets. I said why would you do that with the price of jets? Don't get me wrong I'm as cheap as the next guy but even I never understood doing that. Especially when you pay for drilling the jets is as much as a set of new jets.

I've never fully understood the "desire" to drill jets out firstly for the economic reasons stated, but also there is no going back if you miscalculate the size, or may need the other jets for altitude etc. down the road. Also if you buy new jets you know the size for certain, who's to say existing jets may not already have been tampered with. I would also argue that drilling isn't an exact science depending on how it's done and who's doing it, more material can be removed than intended.

This is true. In the past working in a HP shop, we drilled jets, soldered them and drilled them again. Same with the emulsion tubes. Not for the first timer for sure. :whistle:
Steve

Patton wrote: Perhaps not applicable to the bike at hand, but would check for the following possibility that can happen on Z1 models with the stock air-box configuration.

When there's a crankcase vent tube that exits into the air-box, presence of raw gasoline in the carb throat (from whatever reason) may flow backward toward and into the air-box.

Raw gasoline that gets inside the air-box would intuitively be expected to escape via a drain hole, likely through a hose attached to the drain hole which allows the raw gasoline to exit onto the road surface or garage floor or wherever.

BUT, raw gasoline that gets inside the air-box -- instead of discharging via a drain -- might flow down the crankcase vent tube directly into the crankcase. Which is a possibility with the Z1 air-box design.

Long story short -- do what's necessary to assure there's no gasoline draining from the air box down through the crankcase vent hose into the crankcase.

Carbs with a functioning overflow circuit usually avoid raw gasoline in the carb throat because the maximum float bowl fuel level is governed by height of the overflow tube in the float bowl.

However, when using carbs without an overflow circuit (such as the popular Mikuni smoothbores) -- or any carbs with a non-functional overflow circuit -- a leaking fuel valve (or other cause) may result in raw gasoline rising from inside the float bowl up into the carb throat.

Good Fortune!

I didn't check with the airbox boots off yet but before I took them off there was gas leaking from where the vent hose connects to the airbox.
I need to look but wouldn't these carbs have an overflow hose?

Not the early ones or my 33's. Had the same problem.
Steve