Carb Settings and Notes for '70-'71 Yamaha XS1-XS1B
Note: There are various casting versions for this carb. The setting listed are for the most common. This carb is not super common anymore and it is very hard to determine the exact style you have because the ID is very rarely readable on the carb.
Mikuni Type First Gen BS38
Carb ID 256 (W1 and E2 Casting)
Main Jet - 130
Idle Jet - 45
and later 42.5 (BS30/96)
Fuel Passage Plug - No
Jet Needle - 4JN19-4
Needle Jet - Z6
Float Height - 25mm +- 1mm
Air Screw - 1 Turn
Carb Settings and Notes for '72 Yamaha XS2
Mikuni Type First Gen BS38
Carb ID 306
Main Jet - 130
Idle Jet - 42.5 (BS30/96)
Fuel Passage Plug - No
Jet Needle - 4JN19-4
Needle Jet - Z6
Float Height - 25mm +- 1mm
Air Screw - 3/4 Turn
Carb Settings and Notes for '73 Yamaha TX650
Mikuni Type First Gen BS38
Carb ID 306
Main Jet - 130
Idle Jet - 42.5 (BS30/96)
Fuel Passage Plug - No
Jet Needle - 4JN19-4
Needle Jet - Z6
Float Height - 25mm +- 1mm
Air Screw - 3/4 Turn
Carb Settings and Notes for '74 Yamaha TX650A
Mikuni Type First Gen BS38
Carb ID 447
Main Jet - 130
Idle Jet - 45 (BS30/96)
Fuel Passage Plug - No
Jet Needle - 4N8-4
Needle Jet - Z6
Float Height - 25mm +- 1mm
Air Screw - 3/4 Turn
Carb Settings and Notes for '75 Yamaha XS650B
Mikuni Type First Gen BS38
Carb ID 447
Main Jet - 130
Idle Jet - 45 (BS30/96)
Fuel Passage Plug - No
Jet Needle - 4N8-4
Needle Jet - Z6
Float Height - 25mm +- 1mm
Air Screw - 3/4 Turn
Carb Settings and Notes for '76 Yamaha XS650C
Mikuni Type First Gen BS38
Carb ID 584
Main Jet - 122.5
Idle Jet - 25 (VM22/210)
Fuel Passage Plug - No
Jet Needle - 4M1-3
Needle Jet - Z8
Float Height - 25mm +- 1mm
Air Screw - 1.5 Turn
Carb Settings and Notes for '77 Yamaha XS650D
Mikuni Type First Gen BS38
Carb ID 3G1-00
Main Jet - 122.5
Idle Jet - 25 (VM22/210)
Fuel Passage Plug - No
Jet Needle - 4M1-3
Needle Jet - Z8
Float Height - 25mm +- 1mm
Air Screw - 1.25 Turn
Carb Settings and Notes for '78 Yamaha XS650E and XS650SF/2F
Mikuni Type First Gen BS38
Carb ID 2F0-00
Main Jet - 135
Idle Jet - 27.5 (VM22/210)
Fuel Passage Plug - No
Jet Needle - 502-3
Needle Jet - Z2
Float Height - 24mm +- 1mm
Air Screw - 2.25 Turn
Carb Settings and Notes for '79 Yamaha XS650SF/2F
Mikuni Type First Gen BS38
Carb ID 2F0-00
Main Jet - 135
Idle Jet - 27.5 (VM22/210)
Fuel Passage Plug - No
Jet Needle - 502-3
Needle Jet - Z2
Float Height - 24mm +- 1mm
Air Screw - 2.25 Turn