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Thread: 1980 GS850G with 4 into 1 V&H and K&N filter - what main jets?

  1. #1
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    Default 1980 GS850G with 4 into 1 V&H and K&N filter - what main jets?

    Hey guys, my 82 GS850G has a Vance and Heins 4 into 1 pipe and a K&N Air filter. And it's breaking up badly after about 1/2 throttle. I opened the choke during the break up and it got worse and fell on it's face so I'm pretty sure the main jets are too small.

    I have not opened up the carbs yet but was wondering if any of you that have an 850 and slapped on a V&H pipe and an air filter.. what Jet's did you end up using? (Figured I'd save some time trying new ones)

    Stock is as follows:
    GS850 (80) the specs are for the CV's

    idle.................... 1050 +/- 100 r/min
    carb................... mik BS32SS
    id no................... 45120
    bore size ............ 32 (1.26)
    float height ......... 22.4 +/- 1.0 (0.88 +/- 0.04)
    fuel level ............ 5.0 +/- 0.5 (0.20" +/-0.02")
    VALVE SEAT........ 2.0
    STARTER JET....... 32.5
    PILOT SCREW ..... 3.5
    PILOT AIR JET ..... #200
    pilot jet............... #42.5
    jet needle........... 5D57-3 (the -3 3rd notch)
    needle jet .......... X - 6
    pilot outlet........... 0.7
    BY PASS............. 1.0, 0.8, 0.8
    MAIN AIR JET...... 1.7
    main jet............. #115

  2. #2
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    Half throttle is the needle, and the main jet had little effect
    Most people go to a jet kit, like Dynojet to get a better needle
    1978 GS 1000 (since new)
    1979 GS 1000 (The Fridge, superbike replica project)
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    1981 GS 850 (anyone want a project?)
    1981 GPZ 550 (backroad screamer)
    1970 450 Mk IIID (THUMP!)
    2007 DRz 400S
    1999 ATK 490ES
    1994 DR 350SES

  3. #3
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    Easiest solution would be to go back to a stock filter and you can use the stock jetting.
    2@ \'78 GS1000

  4. #4
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    Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

    What baffle is in the V&H pipe?

    Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

    .

    mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
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  5. #5
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    Quote Originally Posted by Steve View Post
    Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

    What baffle is in the V&H pipe?

    Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

    .

    Single filter in the orig sealed air box, and full baffle, The bike is not loud.

    Thanks in advance.

    3.jpg

  6. #6
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    There is a decent chance you may not have to re-jet.

    The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

    With a quiet baffle, flow might not be much more than stock, so not much will change there.

    At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

    I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

    .

    mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
    hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
    #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
    #2 son: 1980 GS1000G
    Family Portrait
    Siblings and Spouses
    Mom's first ride
    Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
    (Click on my username in the upper-left corner for e-mail info.)

  7. #7
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    My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.
    GED

    1980 GS850G (BLACK)
    http://www.thegsresources.com/_forum...d.php?t=185562
    1980 GS850G (RED) http://www.thegsresources.com/_forum...d.php?t=219169
    1980 GS850G (SILVER)

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  8. #8
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    Quote Originally Posted by Steve View Post
    There is a decent chance you may not have to re-jet.

    The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

    With a quiet baffle, flow might not be much more than stock, so not much will change there.

    At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

    I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

    .

    Excellent info thanks!

  9. #9
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    Quote Originally Posted by ged View Post
    My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.

    I will double check this! Thanks!

  10. #10
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    salty_monk is offline Forum LongTimer GSResource Superstar
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    I used that setup on a 1000G. I liked it. Better than pods.

    You don’t need to go up much. I think I ran 122.5 (stock 117), pushed the needle up a bit using washers and ran the air screws at about 3 turns out. I am at sea level.

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