carb changes and timing

Discussion in 'Engine, Fuel and Exhaust' started by nmaineron, May 19, 2011.

  1. nmaineron

    nmaineron Member

    I have a 94 FX Springer with an EV 27 and a White Bros exhaust that I did some changes to this winter.First I changed the needle to the 88 sportster needle,I am running a CV Carb BTW,plus I changed the low speed jet to a 42.All feels great except I have a very soft bog in fifth on a hard excel.Everything feels great except for this and it is so soft that I don't think I need to re-jet.Plugs look great!

    I set my timing by the book,always have and never experimented otherwise and I'm thinking I might be able to tune this little soft spot out by turning my plate a bit,but which way? I'm at your mercy! Thank,Ron
  2. glider

    glider Veteran Member

    Two things I see is a 42 low jet that is a bit small and the sporty needle that was made for a CV carb with no accelerator pump. The two are working against each other. The taper on the sporty needle is larger/faster than the standard needle and will add more than needed fuel. Your fuel metering goes from lean with the 42 into a rich condition as the needle raises possibly the cause of your bog.
    Run the bike through the gears into third gear and run third up to 60-70 MPH full throttle, then chop the throttle about 1/8 to 1/4 back and see if the bike either surges ahead or stumbles then recovers.

    If it surges ahead, your jetting is lean

    If it stumbles and recovers , your jetting is rich
    If it makes no difference, you're pretty close.

    Plugs will not tell the story any more with todays fuels. They will just show the additive packages added to the fuel as a color on the insulator.

  3. ckhismine

    ckhismine Active Member

    Glider is correct on the carb jetting. A neat way to set the timing on a evo is in the link below

    A Neat Timing Trick
  4. nmaineron

    nmaineron Member

    Wow, Glider our info on the sporty needle has me scratchin my head.The only reason that it is in there is because of all the hype made of it being the needle to have if you want your CV to perform at its best.

    Where I'm at is very close,I changed out a 45 because I was playing with trying to get the mixture screw to make a difference and couldn't,I can turn it all the way in and still have a strong idle.The 42 gives me a snappy throttle and a good idle at 2 1/2 turns.

    One thing that I have noticed is that my fuel mileage has taken a dump by almost 10 MPG with the 88 needle in there.I really ad no complaints with how it ran with the other needle cept I just have to play around.I'm thinking that needle has to come out.Any suggestions on a needle?
  5. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Perhaps going back to the original needle with a couple of washers under the seat to raise it slightly to get on the taper sooner may be something worth trying

  6. nmaineron

    nmaineron Member

    Thanks Brian,I may do that but I really had no issues with the other setup.I was just curious as to how the ole girl would run with the sporty needle in there.Thanks again,Ron
  7. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    You really have to be aware of idle speed and how far open the butterfly is when making your idle mixture adjustment. If the butterfly is open to much you may be taking the idle mixture port ineffective.