Z650- fuel consumption

i just pulled the plugs. they are all black, sooty and dry. each is in the same condition.

the bike only smokes noticeably when i rev the engine while i'm stopped. if it also smokes while i'm riding i've not noticed.

so, where should i start looking? judging from the condition of the plugs, the engine is running rich, correct?

-bt

also, i have NGK B7ES plugs, which i believe are the Normal Heat Range plugs for this bike. i do have a aftermarket foam air filter, which i cleaned not too long ago (which involved removing the gunk and re-applying new oil to the filter. i think i did it correctly). this bike has gotten this type of mileage for as long as i've owned it...about 7 years (although i haven't really ridden it much for the past 5 years)

Post edited by: bionicTechnophobe, at: 2006/04/28 11:56

What rpm do you all shift and cruise at?

I almost never switch gears below 5000 rpm. I would say on average, I shift at 6000~7000 rpm.

I also find that I will cruise at approx 80-90 kph/ 50-56 mph, as I live in the country, but leave it in 4th gear at approx 5000 -5500 rpm. If I switch into 5th, the revs drop down to 4000 rpm, and find this too low.

Maybe this contributes to my lower overall milage?

Also, my cylinder head has had some porting done to it, helping it flow more. And probably lowering my range?

The NGK B7ES plug is correct for the B2A per my Kawasaki service manual. I'm certainly no tuning expert so these are just some ideas.

What position are the needle clips? The service manual specifies that position 3 (the middle of the five) is the factory setting. It's possible they were raised for some reason.

The service manual offers the following in the troubleshooting section:

Black smoke

Air cleaner clogged
Main jet too large or fallen off (this happens?!)
Starter plunger stuck open
Fuel level too high

and:

Fuel/air mixture incorrect
Main jet clogged or wrong size
Jet needle or needle jet worn
Fuel level too high or too low
Air bleed pipe bleed holes clogged
Air cleaner clogged, poorly sealed or missing
Air cleaner duct poorly sealed
Starter plunger stuck open
Water or foreign matter in fuel
Carburetor holders loose
Fuel tank air vent obstructed
Fuel tap clogged
Fuel line clogged

Some of these in the second group are obviously not your problem (would result in fuel starvation) and others you've already addressed. The obvious culprits would seem to be the starter plungers not closing completely or the needle clip set too low resulting in the needle being too high.

If the needles are reassembled incorrectly, the mixture could still be too rich even with the clip in the correct position. There are two plastic washers one above and one below the clip with a spring below all of them. One washer is thinner than the other and it belongs below (toward the pointed end of the needle) the clip and the thicker one above. If those are reversed it would richen the mixture.

I had a carb that was running rich and I found both washers below the clip! The previous owner had made a simple mistake on reassembly and it was a learning experience for me finding that one.

- Nate >>