Kz1100 running very rich

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.

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!

eddiem wrote: . . . I need to look but wouldn't these carbs have an overflow hose?