'79 kz400 carb draining

soon as I turn the fuel on, it comes pouring out of my port (left) carb from the bottom of the bowl - a steady stream.(the drain tube was tied in a knot) Got the bike free, pulled the carbs and they seem clean, just pulled the bowls and made sure the floats weren't stuck. ALSO - the primary jet in both carbs had a machine screw wrapped with plumber's tape shoved up the hole. Primary is the one offset from the center of the carb when held upside down, right?
1st, how to stop the draining
2nd, why plug a jet?
3rd, best fix?
thanks all
jon

qool67 wrote:

soon as I turn the fuel on, it comes pouring out of my port (left) carb from the bottom of the bowl - a steady stream.(the drain tube was tied in a knot) Got the bike free, pulled the carbs and they seem clean, just pulled the bowls and made sure the floats weren't stuck. ALSO - the primary jet in both carbs had a machine screw wrapped with plumber's tape shoved up the hole. Primary is the one offset from the center of the carb when held upside down, right?
1st, how to stop the draining
2nd, why plug a jet?
3rd, best fix?
thanks all
jon

Hello Jon! Good to see you on the forum.

Often, incomplete closure of the float needle/seat interface (leaking float needle) allows fuel to keep on coming into the float bowl. The float bowl overflow circuit is designed as an escape route for the excess fuel which passes from a nipple on bottom of the float bowl and on through a tube from the nipple routed around the swing arm to underneath the bike. This may happen regardless of a properly functioning float.

A sticking float may also cause the over flow by failing to push the float needle up into and against its seat. This may happen regardless of an otherwise perfectly sealing float needle/seat interface.

And of course a damaged or worn out float needle and/or seat may fail to seal off the incoming fuel as they are supposed to.

Would here first suspect crud or grit lodged in the float needle/seat interface. Often resolved by a good cleaning.

This is the main reason why it's so important to always use an in-line fuel filter.

ALSO - the primary jet in both carbs had a machine screw wrapped with plumber's tape shoved up the hole.



Sure don't see that very much.
Pic???

Good Luck!

For reference --- 1979 KZ400 carb

[Click on image to enlarge view]







REF NUMBER PART NUMBER DESCRIPTION QUANTITY US CA CN REMARKS


1 92009-1004 SCREW,PLUG 2


2 92055-1002 O RING,PILOT ADJ 2


3 92022-1003 WASHER,PLAIN 2


4 92081-1002 SPRING,PIROT ADJ SCRW 2


5 16014-1001 SCREW,PILOT ADJUST 2 X USE FOR 16001-1008/-1097, USE FOR 16001-1112 USA


6 11012-3727 CAP,JET NEEDLE 2


7 16005-1001 TOP,MIXING CHAMBER 2


8 220B0408 SCREW PAN HEAD 4X8 7


9 92081-1001 SPRING 2


10 92037-1005 CIRCLIP 2


11 16007-1001 COLLAR 2


12 16009-1010 JET NEEDLE,003303 2 X USE FOR 16001-1008/-1097, USE FOR 16001-1112 USA


13 16126-1042 VACUUM,VALVE 2


14 16017-1001 NEEDLE JET 2


15 13091-1019 HOLDER,NEEDLE JET 2 X USE FOR 16001-1008/-1097, USE FOR 16001-1112 USA


16 92063-1003 MAIN JET,2ND,#90 2 S.T.D., RACING USE ONLY, RACING USE ONLY, RACING USE ONLY, RACING USE ONLY


17 92062-1001 NOZZLE,MAIN 2


18 92063-1002 MAINJET,PRIMARY,#70 2


19 92064-1001 PILOT JET,#35 2


20 16012-1001 CAP,RUBBER 2


21 16030-1007 FLOAT VALVE 2


22 16044-007 CLIP,FLOAT VALVE 2


23 16031-1001 FLOAT 2


24 92043-1002 FLOAT PIN 2


25 16019-024 "O" RING,FLOAT BALL 2


26 461F0400 WASHER SPRING 4MM 8


27 220B0412 SCREW-PAN-CRSOSS,4X12 8


28 92055-1003 "O" RING,DRAIN SCREW 2 USE FOR 16001-1008


29 92009-1003 SCREW,DRAIN 2 USE FOR 16001-1008


30 92009-1095 SCREW,DRAIN 2 USE FOR 16001-1112/-1097


31 92055-1053 "O" RING,DRAIN SCREW 2 USE FOR 16001-1112/-1097

hey, thanks for the speedy replies, I'll replace my "adjustment" to the jets and start cleaning. (And here I'm thinking "what knucklehead put this rinky dink machine screw in here?!")
Thanks again,
Jon

Hi Jon,

Is the adjustment you mentioned the plug (#20) over the pilot jet? I remember asking Wired George about those and I think he said they're needed to draw the right amount of vacuum through the pilot system and are basically there to provide access to the pilot jet.

I don't believe I ever said that exactly. The plug atop a pilot jet is necessary as the design of the that particular carb assembly will have the pilot jet drawing gas through a hole between the pilot well and main jet well. If the pilot well is unplugged in this type assembly, it will be very rich at idle and run poorly through the RPM range. The primary main jet should be atop a pickup tube and not plugged. The primary main jet works in conjunction with the jet needle to meter gas at mid-range.

The correct jets must be used for the assembly to work properly. In addition, the flooding issue... clean the float seats using a q-tip and brasso to ensure they are as clean/smooth as possible, install new float needles and set the float level using the service fuel level method (clear plastic tube next to bowl). This technique is described in a most any service manual and many times on this board.

Sorry WG, didn't mean to mis-quote you....that is what you had told me.

hey, thanks again for the quick and thorough answers - I really appreciate it, and the exploded view of the carb too!
jon