Carburetor Rebuild now MPG is only 62 MPG
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Thread: Carburetor Rebuild now MPG is only 62 MPG

  1. #1
    Senior Member msmiller's Avatar
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    Carburetor Rebuild now MPG is only 62 MPG

    I rebuilt my 2009 TK carb with a moose racing rebuild kit and used the suggested (from pro cycle) jet setup #125 Main Jet and #34 Pilot with the kits needle and one shim/washer. My intention was to make the bike run a bit cooler as suggested on here. Question is if I am using more gas does this mean I am now running with a "cooler" setup? MPG used to be 75-78 MPG first full tank MPG now 62 MPG. Bike runs fine. Thank you for your time. M

  2. #2
    Senior Member SportsterDoc's Avatar
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    I tuned both Harleys with a combination of plug reads, throttle response and an oil tank temperature gauge.
    Going richer than factory brought the oil temp down ~ 20 F on sustained grades.
    It also dropped MPG ~ 14 %.
    I would look up posts on Sportster.org, to check my memory, but it ceased in 2012.

    From memory, going up interstate 5 from Los Angeles with the 1200 Sport, stock was almost 60 MPG (1200 cc, dual plug heads, W grind cams).
    Again, from memory, the same trip, after rejetting, dropped from 60 MPG to 52 MPH.

    This was on a Keihin CV40 carb, with mixture at 2 3/4, pilot from 42 to 45 (0.45 mm), needle N65C (stock for 1988, with no accelerator pump) and 195 main reamed to 203 (2.03 mm). So it was made richer every which way.

    BTW, both Sportsters were California models, the leanest of the three produced by Harley at that time (CA, 49 state and international), so base was very lean.

    However, if too rich, the mixture can "wash down" the cylinder walls to dilute crankcase oil, darken plugs and send unburned fuel (black smoke) out the exhaust.

    Riding to over 8,000 feet elevation, my TW performed very well with only a mixture screw adjustment (from 1 1/4 turns out from factory to 2 3/4 turns out from gentle seat)

    Bottom line, how do your plugs look?
    Does it seem to run any cooler?
    Instead of hesitating, if it was lean, does it now blubber from too rich?

    If any rich symptoms are present, I would first remove the needle shim.
    Last edited by SportsterDoc; 03-01-2018 at 11:48 AM.
    msmiller, littletommy, Ken and 1 others like this.
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  3. #3
    Senior Member msmiller's Avatar
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    Bike seems to run fine maybe lacking a little zip but i weigh as much as the bike. I will check the plug over the weekend to see what it looks like.

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  5. #4
    Senior Member SportsterDoc's Avatar
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    Here is what I posted for TW mileage:

    Initial around Red Rock Canyon Loop for break-in was 78 MPG.

    Once I started working it, it dropped...

    I am not a big fan of shims and most riding is mid range (using the needle).

    After I dialed in the 1200 Sport with what I posted in post #2, I shimmed the needle and performance dropped.

    https://tw200forum.com/forum/general-...s-today-2.html

    https://tw200forum.com/forum/trails-o...on-return.html
    2014 Honda CB1100
    2018 Yamaha XT250
    2016 Moto Guzzi V7 II
    2017 Yamaha TW200
    2012 Triumph Bonneville
    2002 H-D Sportster 1200 Sport
    2003 H-D Sportster 883
    1976 Honda CB750F
    1975 Honda CB360
    1970 Yamaha CT1
    1972 Yamaha CT2
    1972 Yamaha AT2/CT2
    1970 Honda SL350
    1970 Honda CL350
    1967 Honda CL160
    1967 Honda CB160
    1962 Honda CA110

  6. #5
    Super Moderator littletommy's Avatar
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    You will take a hit on gas mileage and it would run cooler.
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    Senior Member elime's Avatar
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    Were there signs of overheating?

    I run my TW's lean and tend to ride them hard, albeit asphalt riding. I have had zero problems with overheating or burned pistons or valves. You must be riding it easy to get 75 to 78 mpg. If it ran well I would have left it alone.
    Long live the internal combustion engine!

  8. #7
    Senior Member jtstdub's Avatar
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    Bone stock my head temp in 105deg weather runs in the 315-330 range. <>75mpg . Traffic, hills etc.

    Jim
    Hidden Content 2003 Tw200, 2014 BWS 150, 1969 VW Beetle Baja, 1972 Super Beetle and a 1987 Suzuki Samurai.

  9. #8
    Senior Member DougDotyTW200's Avatar
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    I have not done any mileage testing on mine but it seems odd to me that the Moose kit comes with a 125 jet when stock is 126 and mileage dropped. Would this be because their jets are non oem and the #'ing system does not correlate or are they making up for it with needle shape and height. The only known here is that it uses more fuel and the mileage dropped which means it will likely run a bit cooler.
    2016, stock'ish and a 2003 Starting on a 225 or bigger 6 speed build as a spare for now and install later when done and ready on this bike.

  10. #9
    Senior Member grewen's Avatar
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    i put the same kit in mine and it turned it into a brand new bike. i was so impressed on how much better it ran. yes i lost about the same mileage as you, but it was worth it. also if you hold the 125 jet up to the light, you will see it is actually bigger than the stock 126. i'm guessing it ran cooler as i never had an overheating problem
    Last edited by grewen; 03-01-2018 at 12:43 PM.
    Greg

    2019 honda cb500x
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  11. #10
    Senior Member msmiller's Avatar
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    Quote Originally Posted by DougDotyTW200 View Post
    I have not done any mileage testing on mine but it seems odd to me that the Moose kit comes with a 125 jet when stock is 126 and mileage dropped. Would this be because their jets are non oem and the #'ing system does not correlate or are they making up for it with needle shape and height. The only known here is that it uses more fuel and the mileage dropped which means it will likely run a bit cooler.

    Exactly the #'s on my rebuild kit are not the same as stock but thankful procycle stick a note in the package with their suggested setup. I used that and the bike started first try. Been riding everyday for a week (to work nothing fun) bike performs like it used too just getting less MPG. M

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