Poor fuel economy

I have my kz1000st and in my opinion it is eating fuel. I average 10 ams per litre. So on a fill of about 16 liters I get about 150 km,I drive about 4km each way 2 is highway the rest is light city traffic. The bike works well I really don't want to screw with the carbs but my car gets the same milage!!

I do have a header and new plugs and a kn air filter . The bike could be running a bit rich. Any feedback would be appreciated.

2bskor wrote: I have my kz1000st and in my opinion it is eating fuel. I average 10 ams per litre. So on a fill of about 16 liters I get about 150 km,I drive about 4km each way 2 is highway the rest is light city traffic. The bike works well I really don't want to screw with the carbs but my car gets the same milage!!

I do have a header and new plugs and a kn air filter . The bike could be running a bit rich. Any feedback would be appreciated.

Would first sniff-test the crankcase oil and examine its condition to determine whether gasoline has contaminated the oil.

Next, would perform the clear tube test to assure fuel levels in carb float bowls are within specs.

Many things besides carb issues can contribute to poorer fuel mileage, both engine and chassis related.

Good Fortune!

I would check the coil voltage and valve clearance.

I have CV 34 carbs on my bike and the best fuel mileage is 52 mpg. Roy

Thanks. The coil voltage is perfect. I did the WG mod and put new coils on this winter. I did think about fuel in the oil. I can't really smell it but the sight glass has a beige foamy substance behind it , even after a new oil change. The filler cap also has a frothy almost whip cream beige sludge in it. The oil is normal when drained. What is the tube test?

2bskor wrote: ...What is the tube test?

I'm having similar fuel mileage concerns on my '81 KZ750 H2. Last tank was only around 21 mpg.

Where is the spot one would check the crankcase oil for fuel? When I change the oil I do not smell any gasoline. Should I just pull off the oil-fill cap and smell there?



Just yesterday I ran a 10ga wire from the battery connection on the solenoid to the coils to see if it is a coil voltage issue so I may have already solved my problem, though I'll find out on the weekend.

kz750saskatoon wrote: ...Where is the spot one would check the crankcase oil for fuel? When I change the oil I do not smell any gasoline. Should I just pull off the oil-fill cap and smell there?....

A "dip-stick" into the oil filler hole should produce enough oil for a sniff-test, and possibly enough to examine the physical condition of the oil.

A thin wood dowel is one option for a "dip-stick."
A bulb style "turkey baster" also works pretty well to draw an oil sample from the crankcase.

Good Fortune!

"the sight glass has a beige foamy substance behind it , even after a new oil change. The filler cap also has a frothy almost whip cream beige sludge in it."

That creamy beige sludgy stuff is moisture. I would suggest a good 30km ride or more so that the motor warms up fully and the moisture evaporates. Does not answer your fuel economy question though.

I would start with the maintenence chapter of your service manual.

Compression check. Valve lash inspection. Plug condition. Oil change. Etc... You know, a complete correct tune-up.

Take a few hours to pull all of the electrical connections apart, including using a pin to remove each small connector inside the larger connectors, one at a time, and scrub and scrape them till they are shiney new. Assemble with some die-electric grease around the boots to prevent moisture intrusion.

Good luck.

I don't know what it equates to in km per litre, but on my '77 KZ650-C1 I've never gotten more than 35 - 40 MPG since it was new. I will admit, however, that I do ride in a somewhat "spirited" fashion. Ed

It would roughly be 24 mpg or a guzzler!!

Sorry to hijack this thread partially.

When I did a compression check last year I got 105 or 110 PSI across all the cylinders. That seemed low to me but it seems to run okay, even though the mileage is low.

Valve clearances was also checked and I remember it being within specifications according to my Clymer manual.

I'll pull the plugs after a longer ride this weekend to see what they look like with the 10ga cable to the coils.

Like I said, maybe I have already narrowed the problem to electrical connections. That is something I am a bit hesitant to do as the wiring seems like a big mess on my bike.