Carby Evolution

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The following table and descriptions outline the evolutionary changes to the carburetors used on all XS/TX 650 Yamahas.

All specs taken from the microfiche. All other observations taken from carburetor body comparisons themselves. Changes are listed as the year changed. To find your carburetors start at the first year listed till you find something different than what is listed then go to the next year listed. Keep following this till you arrive at your year. If an item is listed as a change in a year it follows through for all following years till noted again. 
Some model numbers do not represent Australian models.
1970 XS1 1971 XS1B 1972 XS2 1973 TX650 1974 TX650A 1975 XS650B 1976 XS650C 1977 XS650D 1978 XS650E 1979 XS650F 1980 XS650G 1981 XS650H 1982 XS650J 1983 XS650K
Body Model #  256-00 447-00 584-00 2F0-00 3G1-00 5V4-00
Body Part # 306-14901/2-03-00 447-14901/2-00-00 584-12901/2-00-00 2F0-12901/2-00-00 3G1-12900-00-00 5V4-12900-00-00
Main Jet 130 127.5 122.5 135 132.5
Air Jet 1.2 1.0 1.0 1.0 1.0 1..0 1.0/1.4
Needle Jet Size/Length to meeting of body from end  Z-6 12.5mm Z-6 8mm Z-8 8mm Z-2 8mm Y-0
Jet Needle-Clip Position 4JN19-4 4N8-4 4M1-3 502-3 5HX12-Fixed (USA)
Pilot Jet 45 42.5 45 25 27.5 42.5
Pilot Screw Type 1 Type 2 Type 3 Type 4
Pilot Screw Setting 1 .25 1.5 +/- .5
Starter Jet .6 .7 1=80/2=.5
Float Level 25mm 25mm +/- 1mm 24mm +/- 1mm 27.3 +/- .5mm 22 +/- 1mm
Butterfly 125 120 135


XS1 (1970) 

Bodies

Yamaha Series 256

Solex Bodies.

Bottom of Venturi has raised floor

#125 Butterfly plates.

Throttle cable connectors are dual 2 finger style. 

Fuel crossover tube through 90 degree fittings.

Choke assembly mounted to left side of carburetor body.

Choke lift arm on left side of carburetor body.

Choke assembly connected by a flat metal strap.

Emulsion tube/Main Nozzle Z-6 and is 12.5mm long where it meets into the body

Pilot Jet 45.0.

Butterfly shafts have end caps.

Bell housing (air box end) has 2 molded in orifices (non removable jets).

Intake mounting - 47mm

Type I pilot screw (brass, threaded head straight shank then a taper)

Depression for overflow tube on carburetor body is 9.5mm deep from gasket surface

Enrichening tube is on same side as the overflow tube recess.

Float Bowls

Float bowl overflow hose connected to a plastic 90 degree nipple.

Float bowl has enrichening circuit pickup tube on right when looking at it upright mounted on the carb.

Enrichening tube pickup is on same side as the overflow tube.

Enrichening tube protrudes 10mm above gasket surface on the float bowl.

XS1B (1971)

Pilot Jet 42.5.

XS2 (1972)

Bodies

Choke assembly mounted to right side of carburetor body.

Choke valve capped off on right hand carburetor (#2). Choke for #2 is via a cross over tube

Butterfly shafts no longer have end caps.

Float Bowls

Enrichening tube moved opposite overflow tube

Float bowl stamped "A" on bottom center.

Will only fit on 72/3 models.

TX650 (1973)

Throttle cable connectors are dual ring and barrel style. 

TX650A (1974)

Bodies

Mikuni Bodies 

Raised floor removed in venturi and has a round bottom there.

Emulsion tube/Main Nozzle Z-6 and has been reduced to 8mm long where it meets into the body

Yamaha Series 447

#120 Butterfly plates

Pilot Jet #45.0

Depression for overflow tube on carburetor body is 6.5mm deep from gasket surface

Float Bowls

Float bowl stamped "H" on bottom center.

Will fit on 72/3 models but overflow system will not work as designed. But may work better? Since overflow is 3mm lower than previous years.

XS650B (1975)

Identical to 1974

XS650C (1976)

Bodies

Yamaha Series 584

Throttle cable connectors are single ring and barrel style.

Carburetor synchronization assembly introduced.

Carburetor synchronization access ports/screws added

Reintroduced right carburetor choke assembly.

Z-8 Emulsion Tube/Main Nozzle

Type II pilot screw (same as type I but has a knurled head added to the top of it)

Pilot Jet #25.0

Enrichening tube protrudes 20mm above gasket surface on the float bowl.

Float Bowls

Float bowl overflow hose connected to a brass nipple molded into bowl.

XS650D (1977)

Float bowl overflow hose nipples removed.

XS650E (1978)

Bodies

Yamaha Series 2F0

Bell housing (air box end) has 4 molded in orifices (non removable jets).

Z-2 Emulsion Tube/Main Nozzle

Type III pilot screw (steel, with integrated o-ring on screw)

Pilot Jet #27.5

Float Bowls

 

XS650F (1979)

Identical to 1978

XS650G (1980)

Yamaha Series 3G1 (3W6 for Australian Models)

#135 Butterfly plates

Pull knob choke assembly

Chrome diaphragm covers

Fuel tee instead of individual spigots.

Removable main air jet from bell housing.

Intake mounting - 42mm

Top mounted pilot screw.

Type IV pilot screw (brass, just like type one only longer with a smooth smaller diameter boss for the screwdriver slot).

Pilot Jet #42.5

Float Bowls

Only a bowl. No jets at all in the bowl.

Float bowls have side access drain screws.

Float bowl nipples have no hose nipples for hoses but they do have drain bosses.

XS650H (1981) 

Identical to 1980

XS650J (1982)

Yamaha Series 5V4

Black paint on bodies

Steel brackets has black oxide coating

Screws have black oxide coating

Cable operated choke

XS650K (1983)

Identical to 1982

If anyone has Australian model numbers or knows of variations that should be noted on this page, please let me know at xs650@xs650.org.au and if I can confirm this information I will include it.