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2 Carb questions

Discussion in 'XJ Technical Chat' started by Scott Leithead, Jan 23, 2020.

  1. Scott Leithead

    Scott Leithead New Member

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    1. restored '82 maxim using Haynes manual. carb main and pilot air jets appeared to be wrong in specs list. then reverses them in the pictorial install section. What is the correct size match ? main fuel 110, main air 205 or main fuel 110 , main air 50?
    2. the pilot fuel metering screws show beginning turns out "2-1/2". it stumbled off idle so I turned them at 1-1/2 and worked better but still not a smooth transition. at 4,400 ft. above sea level. any Ideas?
     
  2. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Main fuel jet-110
    Idle jet is probably 40

    airjets— the higher number goes in the hole toward the enricher plunger, and the lower number goes toward the airbox

    If your jets are not matching what you should have, the rack was probably replaced at some point. The bodies are the same for 650/750 but jetting is different.

    did you do a running sync.... not just playing with the mixture screws?
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    air jets jets.jpg
    sounds like you have a 650?

    Y
    Years & Models: 1980-1 XJ650 Maxim, Midnight Maxim, and XJ650RJ and RJC Seca Canadian models
    Carb Manufacturer: Hitachi
    Carb Series: HSC32
    Carb Model ID: 4H800
    Main FUEL Jet Size: #110
    Pilot FUEL Jet Size: #40
    Main AIR Jet Size: #50
    Pilot AIR Jet Size: #195
    AIR COMPENSATOR Jet Size: #36
    Starter FUEL Jet Size: #40 (non-replaceable, in float bowl)
    Main jet NEEDLE ID: #Y-12
    Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
    Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")

    Years & Models: 1982-3 XJ650 Maxim USA models
    Carb Manufacturer: Hitachi
    Carb Series: HSC32
    Carb Model ID: 5N800
    Main FUEL Jet Size: #110
    Pilot FUEL Jet Size: #40
    Main AIR Jet Size: #50
    Pilot AIR Jet Size: #205
    AIR COMPENSATOR Jet Size: #36
    Starter FUEL Jet Size: #40 (non-replaceable, in float bowl)
    Main jet NEEDLE ID: #Y-10
    Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
    Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")
    Idle RPM's: 1,050 rpms
     
    Last edited: Jan 23, 2020
  4. Polock

    Polock Well-Known Member

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    small fuel-big air
    big fuel-small air
     
    Franz and chacal like this.
  5. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Size matters
     
  6. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    This is the easiest way to remember the placement...….
     
  7. Scott Leithead

    Scott Leithead New Member

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    Thank you for the reply.
    I just finished reading the "church of clean" article.
    It is a 650( sorry for the ambiguity) and I could not imagine why they would choke off the main with the smaller air jet!
    I have 40+ years experience so it isn't my first rodeo, but there is a first time for everything (hitachi's).
    I did try and sync with a syncpro set but it did not give me what I felt were accurate readings.
    I'll go back in now and recheck everything and see how it ru s after.
    Thanks again for your response and expertise!
     
  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    make sure the main fuel jet and pilot fuel jets where they belong too.

    you can open your profile and add your bike to your signiture line

    82 XJ650 Maxim
    XJ650J
    are both proper ID for your bike
     
  9. Polock

    Polock Well-Known Member

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    the air jet determines the vacuum applied to the fuel jet, the tiny low jet needs lots of vacuum. the high jet not so much.
     

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