Carb jetting on a 74 Z1

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27 Apr 2009 16:57 - 27 Apr 2009 17:32 #285801 by Carr_113
Carb jetting on a 74 Z1 was created by Carr_113
I checked the guts of the carbs (which I believe to be stock) on my newly bought 1974 Z1 and was surprised by what I found. The bike was running like crap when I got it - too rich at idle and too lean everywhere else. The bike has the stock 903cc engine, pod filters, and a Kerker 4-into-1 exhaust. My Clymer manual states that this is the correct setup:

Fuel level - 3.5 mm
Float level - 24 mm
Main Jet - 112.5
Jet Needle - 5J9 - 3rd
Needle Jet - P-8
Throttle Valve Cut - 2.5
Pilot Jet - 20
Air Screw - 1 1/2

This is what I found:

Main Jet - marked 10.5?
Needle Jet - no marking
Pilot Jet - 17.5

My camera crapped out, otherwise I'd take pictures. Like I said earlier, from everything I've seen or read, these are in fact the stock carbs, with a bore of what I measured to be an I.D. on the engine side of 29mm and an I.D. on the filter side of 40mm.

Does anyone know why the carbs would have jets like this, or what application this would serve?

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)
Last edit: 27 Apr 2009 17:32 by Carr_113.

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29 Apr 2009 05:44 #286167 by Carr_113
Replied by Carr_113 on topic Carb jetting on a 74 Z1
...anyone have at least a little feedback for me?


:unsure:

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)

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29 Apr 2009 06:08 #286174 by Russ Jackson
Replied by Russ Jackson on topic Carb jetting on a 74 Z1
I am not an expert but this might help classickawasaki.se/Tekndokument/vmmanual.pdf

Give the experts on this site a little time one of them will chime in...Russ

1976 KZ 900 B1 29 smoothbores, Kerker, Lester Mags
2008 Kawasaki Concours 14 abs

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30 Apr 2009 10:10 #286528 by Russ Jackson
Replied by Russ Jackson on topic Carb jetting on a 74 Z1
Bump..I think if you post a picture someone will help out...Russ

1976 KZ 900 B1 29 smoothbores, Kerker, Lester Mags
2008 Kawasaki Concours 14 abs

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30 Apr 2009 16:40 - 30 Apr 2009 16:41 #286601 by Patton
Replied by Patton on topic Carb jetting on a 74 Z1
Here's a link to Z!E's carb info.
Click > Z1E carb info

Check out the pictures and scroll down to the following chart:

28mm (VM28SC) Z1 & early Z1-A
Main Jet 112.5
Air Jet 1.0
Needle Jet P-8
Jet Needle 5J9-3 - last number is the clip position where 1 is at the top of the needle (leanest) and 5 is at the bottom (richest)
Throttle valve (slide) 2.5mm cutaway
Pilot Jet 20.0
Air Screw setting 1 1/2 turns out

28mm (VM28SC) Late Z1-A & all Z1-B
Main Jet 112.5
Air Jet 1.0
Needle Jet O-8
Jet Needle 5J9-2 (last number is the clip position)
Throttle valve (slide) 1.5mm cutaway
Pilot Jet 17.5
Air Screw setting 1 1/4 turns out

Good Luck! :)

1973 Z1
KZ900 LTD
Last edit: 30 Apr 2009 16:41 by Patton.

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30 Apr 2009 18:46 #286640 by gane
Replied by gane on topic Carb jetting on a 74 Z1
Carr, Pic's would help, I thought 900's & early 1000's used vm 26's , you could have vm 28's, or (not to get hopes up,) a set of 29 smoothbores. Luck G

[img][/img] 1977 KZ1000A1

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30 Apr 2009 20:01 #286664 by oldkaws4ever
Replied by oldkaws4ever on topic Carb jetting on a 74 Z1
Z1's used 28's without the pump, kz 900s and some kz 1000's used 26mm. Some kz 1000's used 28mm with the accelerator pump, like the z1r for instance.

74 Z1a 900 (Apart and making it better than ever)
77 Kz 650b (Threw a rod, going to sandwich in a 900 or 1000 motor)
76 Kz 400d
05 ninja zx-636
81 Kz 750 Ltd
Darien, Illinois

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01 May 2009 05:53 #286943 by shighley
Replied by shighley on topic Carb jetting on a 74 Z1
Carr_113; Here's my two cents worth on the jet marking question. As far as I can tell the main jets are marked by the diameter of the thru hole, measured in millimeters. I've seen aftermarket (non mikuni) jets with the decimal point in the wrong place. That may explain your 10.5, which might be 1.05 mm. When you get down to the thousandths (0.000) of a mm, it is impossible to measure with common tools. Your 112.5 main is really a 1.125 mm diameter. This doesn't seem to work with the pilot jets as a 17.5 doesn't measure 0.175 or 1.75 mm. I'd like to know whats up with that. Always learning. Ride safe, Steve

\'74 Z1-A, Bought new, worn out 3 times, being ridden now
\'83 XVZ12TK, was daily driver until frame broke
\'78 KZ650SR-D1A, Son's bike, I'm the wrench (He's young)!

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01 May 2009 17:29 - 01 May 2009 17:34 #287034 by Carr_113
Replied by Carr_113 on topic Carb jetting on a 74 Z1
Thanks to everyone for your replies! I finally got a camera that works and have taken some pics to try and identify these things.

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)
Attachments:
Last edit: 01 May 2009 17:34 by Carr_113.

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01 May 2009 17:36 #287035 by Carr_113
Replied by Carr_113 on topic Carb jetting on a 74 Z1
another

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)
Attachments:

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01 May 2009 17:37 #287036 by Carr_113
Replied by Carr_113 on topic Carb jetting on a 74 Z1
3/4

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)
Attachments:

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01 May 2009 17:38 #287037 by Carr_113
Replied by Carr_113 on topic Carb jetting on a 74 Z1
side

'74 Z1-A
'80 KZ750E
'80 GS750E
'81 KZ440
'79 XS650 (needs love)
'72-'73 CB350 (3 or 4, in pieces)
Attachments:

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