Carbs

Discussion in 'Softail Models' started by traveller, Oct 2, 2014.

  1. traveller

    traveller Member

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    need to pick the brains of the pro's. I have a 03 FLSTS, I've installed screaming ignition,dual exhaust,s&s 570 easy start cam,600 lift valve springs, 10.5 to 1 pistons,milled heads .050.oil cooler and modified the existing carb,(42mm CV). I know I need more air flow, the question is what size carb venturi in your opinion would I need. thanks for any input.
     
  2. Jennmarr

    Jennmarr Junior Member

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    I can't help you on carb size, but I imagine that whoever can will need to know your engine displacement. Is it still 88", or did you go to 95", or maybe even bigger?
     
  3. dolt

    dolt Senior Member Contributor

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    As Jennmarr points out, displacement would be helpful in answering your question; however, a 42mm CV should be sufficient for anything up to 110".

    You say you have modified the carb; how? What does "carb venturi" mean?
     
  4. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    The carb venture is where the carb throat narrows to create the point of lowest pressure
    A 42 mm carb should be sufficient but personally I do not like keihin cv carbs as the have a tendency to ice in my environment

    Brian
     
  5. dolt

    dolt Senior Member Contributor

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    I know what the carb venture is but not sure the OP does.:s He knows he is running a 42mm CV but wants to know "what size venturi" he needs for more air flow??:shock

    Perhaps he is asking if he needs more than a 42mm carburetor which would have been a better way to ask the question. If that is the question and displacement is not more than the 42mm CV can accommodate; the 42mm CV is adequate for his build. If that's not the question, I still want to understand what the OP is trying to find out.:D
     
  6. GusSimpson

    GusSimpson Member

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    Thinking out of the box....

    I enjoy the ease of tuning the Mikuni HSR42 is why we have them on 3ea. different bikes although most performance shops who think out of the box here on the west coast choose S&S SUPER E. CARBS for ease and function of tuning wether it be on the street or if your setting up on the Dyno machine for performance or on the track...and it is aslo a matter of what most want to spend being you have alot invested already S&S CARB is the ticket

    As for the Mikuni HSR42 still installed on the bike... I can in less than 5 minutes make a mainjet change out, Removing the air breather and carb takes 20 minutes to make a fuel needle clip adjustmernt or fuel needle size swap out, 15 minutes to change out the Pump nozzle with carb still installed providing cap bolt screws are used. for the cost and tunibility of ther Mikuni HSR42
     
  7. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    I was a wee bit confused by the question as I thought you would with your very good technical knowledge would know exactly what the venturie was
    However there is always the chance that as we gather information in our heads wee bits get omitted from time to time

    Brian
     
  8. GusSimpson

    GusSimpson Member

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    Each of changes made or performed are not performed at the same time, otherwise how would you know what change may or may not cure ur issue. :)

    always perform main jet changes seperatley such as 1st the Pilot jet...then the mainjet then fuel needle adjustment, then pump squirt if you have a accel pump. other wise the S&S tunability of the carb installed cuts the time down considerably.

    hope this helps
     
  9. dolt

    dolt Senior Member Contributor

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    Not sure how we got from a 42mm CV to SuperE and Mikuni carbs which are not related the OP at all. I can't speak to the Super E vs the CV but there is plenty of dyno data that shows the CV making more power than the Mikuni at low to mid range rpms, particularly TQ where the Mikuni makes a wee bit more HP at the upper end. As for tuning, both are very easy to tune and, IMHO, the CV easiest simply because there are fewer adjustments. Some may say, "yeah but you can develop a "finer" state of tune with the Mikuni because there are more adjustments" but a carb is a compromise at best and carburetor and fine tuning should never be used in the same sentence. Oops.:shock JMHO.:hii
     
  10. dolt

    dolt Senior Member Contributor

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    Amen brother; I believe that is what we commonly refer to as brain farts, of which I have had my share. I was seeking clarification on the purpose of the OP.:hii