CV Carb Rejet Suggestions

Discussion in 'Engine, Fuel and Exhaust' started by softglide1, May 31, 2011.

  1. softglide1

    softglide1 New Member

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    I am trying to raise the fuel mileage on my brothers bike. 2001 FXDWG carburated. It has the Harley replacement air filter, and Reinhart Bub 2 into 1 exhaust. Started out with a 180 main 45 low speed jets and the adjustable needle. That's when the mileage went down into the 20s. I tried the 185 main and 46 low speed with two washers under the stock needle. This set up made the bike hard to start after riding and stopping to fill up. Blew lots of black smoke after it finally started. Tried to adjust the fuel mixture but didn't seem to matter. Came home and changed the low speed back to 45 and adjusted it to 2.5 turns out. Went riding again mileage came back up to around 34 both of these trips were slower speeds 50-65. Bike would die after idleing a short time, but started right back up. We road on, the next fuel stop mileage was down a little to 31, this was more higway riding at 65. This time I adjusted the air mixture to 3.75 turns to smooth out the idle. I'm thinking about changing the main back to the 180 to see if the needle is coming up and letting more fuel thru than he needs? It seems like your not using much throttle at these speeds and most of it would be coming from the low speed jet.

    Am I missing something? The bike runs great no problem taking fuel, seems to be no surge or falter when you let off the throttle in third gear. Sorry I'm taking so long to explain but more info is better than none.
     
  2. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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  3. BUBBIE

    BUBBIE Well-Known Member

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    If my bike,,, I'd go with a .044 slow jet and see IF it idles good at the 2.5 turns out...NOT just setting it there but turning to find the right running and then check where it is positioned.... I would also PULL out the two washers First under the stock needle and put in the 180 jet..... OR 175...

    Start with What was in the bike When It Ran Good?

    I can't see why you want to go bigger and get better mileage in the same sentence.. IT Doesn't work that way... Bigger jets and raise the needle = Poorer mileage..

    Burning Black tell me WAY WRONG, especially IF it was running good before..

    A good running bike Doesn't need a carb change. I really don't agree to modify the carb when the bike is running good STOCK... Even with modifications,, air and exhaust ,,, some bikes run Good and are NOT Lean..Especially carbed bikes.. changing the slow speed OFTEN cures a lean condition.

    the idle jet by+- .002 to /.003 is a BIG change and the main jet by+- .005 is the usual...

    If you are LEAN then go bigger on the jets. IF FAT on gas GO Smaller..

    The idle jet is IDLE and part of the Running of the bike until about 1/2 throttle.. THEN the big jet kicks in the fuel.. By raising the needle with washers you are getting MORE gas into the engine and SOONER.. BURNING Black is NOT what you need here.

    If you find the low speed jet that works at a good idle and is 2.5 turns out to idle fine ,,, you Probably have the correct small jet...(other things could make a difference,,, baring them,, intake manifold leak etc, etc.)

    signed....BUBBIE
     
  4. glider

    glider Veteran Member

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    Lots of good advice here but one thing overlooked is if you tune these motors for best MPG, more than likely you will have drivability issues. Tune it where it runs best and runs properly and drive it easy if you want better MPG.
     
  5. glazier

    glazier Junior Member

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    On my 2000 Heritage, with the same motor and stock carb as yours, I recently rebuilt the carb, and went to a 46 slow jet (48 was in there) and a 190 main jet was already installed. I added the two washers under the needle and went back to the 48 slow jet. Idle mixture screw is about 2 1/2 turns out and it runs great. Recently went to SE 203 cams and it added a little more power, but did decrease the mpg as did the two washers under the needle, but it runs great now. I'm not worried about my gas mileage. I want my bike running as good as possible. I'm now getting about 34 mpg. Was getting about 38 mpg before the washers under the needle and new cams. Can't believe your mpg went down to the 20's. Don't worry about mileage. It's a bike, not an everyday car. Why are y'all that concerned about the mileage anyway??? Get it running the best possible and live with the mileage. Or else, buy a Honda :D
     
  6. murf

    murf Active Member

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    What do the plugs look like during these adjustments. After warmed up run it a couple miles with each change then check plugs. Plugs may tell you when fuel/air is right. IMO
     
  7. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Like BUBBIE says, going to a richer mixture will LOWER your MPG, so going to bigger jets, turning the mixture screw richer all are conspiring to flood your engine with fuel. You have to go in the opposite direction..."--lean best is considered best volumetric efficiency" but sacrifice power and a bit of drivability...spark plugs will be dark brown (not black or sooty) and your pipes will not be black, nor smell raw gas.
     
  8. BUBBIE

    BUBBIE Well-Known Member

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    **************************************************************
    Harley, Off the Floor new, had my 97 dyna getting 59 miles per gal.. It Hick=upped at every throttle twist...

    Couldn't wait to do the carb ,,, jetted proper.. both idle and main jet along with a full stage one got me down to 43/46 mpg range and running was good...

    My 2000 FXDS carbed was about the same and needed re-jetting as soon as I got home also..Sneezing every now and then.

    Harley gets good mileage but at the expensive Cost of HEAT and TOO LEAN..
    That WILL destroy an engine quickly.. Harley has their motors set right on the AFR range where Damage is Possible from HEAT-LEAN conditions that the regulators insist on (EPA)

    I can't figure my 06 sport R with proper jetting gets 49 miles per gal (great) and it's NOT running Lean... Python 3 exhaust and big sucker air and 46 idle and ? 195 main jet..(bad memory) but running HOT and I don't mean Heat...

    My 09 was at 46/48 MPG new, and too hot-Lean.. MAN, I could feel the HEAT...Now with Modifications and a Great Fueler TFI, I'm getting 40/42 MPG like clock work and it runs Like a Bike Should...

    signed....BUBBIE
     
  9. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    What BUBBIE said regarding his 06 Sporty running at 49 MPG on highway is what I get with my 04 Sporty which is running a bit rich, but I'm good with that, as the DRIVABILITY is key...! :D

    Running in town, my fuel mileage drops by about 5-7 MPG, but that is due to the idle mixture, low speed jetting and raising the needle with 2-3 #4 washers...which makes the fuel come on a bit "fatter" so the bike does not feel like it is lugging when you snap open the throttle. :s
     
  10. softglide1

    softglide1 New Member

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    Thanks for the suggestions and advice. Don't know about the 44 low speed I put the 45 backin it and it's turned out 3.25 to run smooth. Changed the plugs todayand we rode 80miles, they were black but not wet. His bike is set up with 45 low and 180 main. Mine 2006 Softail is 46 low and 185 main, same exhaust and air filter. HIs bike got 34 mpg mine 49 mpg. The difference with the bikes are his no windshield, mine after market fairing, dressser style bags and trunk. Mine shows a little lean on the plugs. I've had it on a dyno, they said it was jetted right and to play with the fuel mixture. Never did make it stop coughing, I eventuall drilled the low speed like we did the shovel head kehin carbs. The cough went away and so did the mileage. Went to big would like to try a 47 in mine. I can turn my fuel mixture all the way in and not stall the motor tho. Would make you think that it was already to big. Maybe I should take the washers off of my needle too.