Carb jet sizes
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Thread: Carb jet sizes

  1. #1

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    Carb jet sizes

    Took my carbs apart on my 97 bird today as there was a bad smell of fuel on tickover and it is extremely heavy on fuel, jet sizes were 145 for cylinder 1+4 and 150 for 2+3. Are the bigger ones suppose to be on the outside? It has a stock filter and aftermarket downpipes + Remus end cans. needle's are not adjustable. Any recommendations on how to set it? Put the bigger jets on the outside maybe?

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  3. #2

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    Re: Carb jet sizes

    No bigger should go to inside. These cylinders are partially shouted by 1 and 4 and run a little hotter. The extra fuel is to help cool them.
    What did your plugs look like when you pulled them.

    I'd go through and make sure to blow out all the passages. Also check your float needle seats for signs of scoring (thin line around seat tip). If they have this they may not be seating properly. It only takes one to get the conditions your describing. You may also want to check the vacuum line coming from your petcock for the fuel shutoff. If that vacuum line is wet or shows witness lines of fuel then it is leaking under running conditions and will give you the same symptoms. Check the floats for signs of fuel soak. If you have a gram scale they should all weigh about the same.

    Once you get it all back together you can check the running float levels. Take piece of clear plastic line and connect it to the fuel drain at the bottom of the carb. Put a u bend in it that loops down under the carb float bowl. Make sure the open end is a above the carb body. The fire the bike on the center stand with the drain screw open and see where the level settles. You want it at about the point where the bowl meets the carb body. Note the point with a marker or pen the close the bowl drain and check the next carb. They all should be equal. If not then the ones off are either float level is misadjusted or the float is starting to saturate.

    Good luck and keep us posted so we can help
    Last edited by beestoys; 05-19-2019 at 11:52 AM.
    Route 191 formerly Route 666 Some say that this section of the
    road has 1100 curves in 95 miles.

  4. #3

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    That's brilliant information, thanks a mill I'll. Keep you posted.
    When I got the bike it was had to start, I changed the plugs and it started perfectly but after a few months it's starting to do the same again so I assume the new plugs are fouled too

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  6. #4

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    Re: Carb jet sizes

    Need to check my thinking here but, 150 sounds bigger than stock jetting to me. I thought it was 140 outter and 142 on the inner cylinders? Hmmmm

    T.
    "Stemmata quid faciunt."

  7. #5

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    Re: Carb jet sizes

    Yep,..just checked the FSM.. 140 for cylinders #1 and #4 and 142 for cylinders #2 and #3 on the main jets. Slow jet size is listed as #42. Jet needle is shown as J5FZ (for the 49 State/Canada version) and J5FU (for California). Pilot screw settings: 2 3/4 turns out for the 49 State/Canada set up,..and 2 1/2 turns out for the California set up. We say here on site that "if your running a stock filter and stock (near to stock?) exhaust system (and that includes having changed out the exhaust cans to a aftermarket twin can slip on design),..that you do not "normally" need to alter the jetting.

    The large inner jets may explain in part your lack luster fuel mileage issue. Do not alter the filter with a high flow aftermarket unit...this almost never works without performance issues (flat spot) at mid throttle settings.

    T.
    "Stemmata quid faciunt."

  8. #6

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    Re: Carb jet sizes

    This next bit may give you a bit of info on what might have possibly been done to your carbs. This attached tuning sheet is what is included with the "Factory Pro" carb tuning kit for the 1100XX. You can see the different stages of tune depending on what you have done to the motor/exhaust system etc. Of note is the idea that you can bump the outer two cylinders so that all carbs are jetted the same with 142's. Factory Pro are all about "best power" and they use the factory Keihin jets sizing format. Do not mix up this info or confuse it with jet sizing as found in the Dyna Jet kits...Dyna Jet uses their own jets sizing format that does not align with the Keihin factory jet sizes. Dyna Jet also use a stepped jet needle/metering rod design. It is reported that this design brings on emulsion tube wear and tear. There are no required "hole drilling" in the Factory Pro mods...but Dyna Jet have you drill the slide pistons to help with throttle response I believe. These may be clues to if you have a jet kit install or not. That 150 inner main jet says that somebody has been in there messing about,..at least in my mind.

    I bought this Factory Pro kit years ago now, and a Ti Force full 4 into 2 into 1 Titanium exhaust system. None of these items have as yet been installed. I got to love the quiet exhaust note of the stock system when on extended touring mode.

    T.
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    Last edited by TigreST; 05-19-2019 at 6:14 PM.
    "Stemmata quid faciunt."


 

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