Simple fuel screw question

I have a 77 kz650b with mikunis. When I unscrew the fuel screws am I adding or removing fuel? I am way too rich, and my screws are set at 1 1/2 turns from softly seated.

Cheers
David

The "FUEL" screw I think you are referring to is the Idle air screw. out more lets in more air and leans the mix and in gives it less air and richens the idle mix. if its running rich on 1/8 throttle and up it is dirty filter or jets may be too large for the altitude. the air screw only affects idle and just off idle transitioning to jets right off the bottom. but I have been wrong, I remember at least once back in about 76. so I may just be talking out my shorts.

Dman

It depends which Mikuni type you have. 1977 should have the pilot screw type. These are adjustment on the bottom of the carbs towards the head. These type turn the screws out to richen the mixture. In 1978 they changed to the air screw type. These have the adjustment on the top of the carbs towards the air intake. On these type turn the screw in to richen the mixture. Some 78s are air screw, some pilot, a few had both even, but 1977 came from the factory with pilot screw type.

The screws in question are on the top of each carb on the airbox side.

RonKZ650 wrote: "1977 came from the factory with pilot screw type."

Some, but not all of them. I bought my bike new, build date is January 1977, and it has the "pilot air adjusting screws" (part #16014-1004) on top by the intakes. These are the only carbs shown in the January 31, 1977 KZ650C1 Exclusive Parts List.

The earlier KZ650-B1 Kawasaki Parts Catalog (June 25, 1976) shows the "pilot adjusting screw" part #16014-018 along with a "limitter cap" part #16012-022 on the bottom of the carb just as you describe.

In the September 30, 1977 Kawasaki KZ650C Motorcycle Parts Catalog that covers C1 and C2 models both carb types are shown. According to this catalog, the (top) air screw type (like mine) was used on frame #16509 to 027500 and on C2 models, and it shows the (bottom) pilot adjusting screws on frame #1 to 016508. However, the guy writing the catalog got it wrong because my bike's frame number is less than 02000 so according to the catalog it would have the bottom type (but it came with the top type). Clearly this catalog is wrong , not only because it is wrong about the carbs on my earlier frame number, but also becasue the parts were already listed and being used when the January Catalog was published (which is when my bike was built).

The screws in question are on the top of each carb on the airbox side.

dman3998 is correct.

Turn side-located pilot air screw IN (clockwise) to enrichen pilot mixture, or OUT (counter-clockwise) to lean pilot mixture.

The pointed tip on the screw interacts with an orifice in the pilot air passage to regulate amount of air allowed to the pilot jet.

Good Luck!

Thanks everyone! Do I have a 78? The title says 77 but the guy I got it from said it might be a 78. Thanks for the input. I am going to get new plugs tomorrow and make an adjustment. The plugs are pretty black in 300 miles and I can tell a difference in performance but it still cold starts just fine. 1/4 turn? I am thinking this might take 1000 miles or so to figure out. BTW it has an airbox and V&H 4-1. Not sure what the jets are but I have feeling they are stock. Screws are set at 1 1/2 from lightly seated.

Cheers mates!
David

Check your frame# and motor# here to find what year your bike is: models.kz650.info/index.htm
Be sure to check both #'s. You may be surprised to find you have a different year motor with your frame. I know I was. When I checked my #'s I realized I had a '78 C2 motor in my '77 C1.

Davestradamus wrote:

...cold starts just fine. 1/4 turn? ... Screws are set at 1 1/2 from lightly seated....

Would go in 1/8 turn steps counter-clockwise to lean the pilot circuit. Usually, the optimal setting is where best low idle performance is determined.

Leaning the pilot circuit should not degrade cold starting ability, because cold starting mostly depends on the separate enrichener (choke) circuit.

Good Luck!

If air screws are to lean can it cause popping/backfire on decel?

sabell wrote:

If air screws are to lean can it cause popping/backfire on decel?

Yes.

Good Luck!