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Running CVP velocity needle. shims?

Discussion in 'Motorcycle Tech Talk' started by Loony, Apr 16, 2018.

  1. Loony

    Loony New Member

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    Got some pics of what was and what is.....

    This is what was in the bike when i bought it and it had the carb fart.

    Don't know what needle it is but it had a plastic spacer 0.8mm

    Cant post pics............

    I then went for the CVP velocity needle without the plastic shim and this appeared to solve the farting.

    cant post pics

    I recently added some really short exhaust pipes and lost power which i live with but talking to a friend he said try a shim under the CVP needle and see if that improves mid range. TBH couldn't really tell but i guess better.
    The shim is 0.6mm and he gave me 2. I have been running one but now have the fart back.

    cant post pics

    No shim but recess in slide.

    cant post pics


    Jets are at 45 pilot 185 Main. if i go any bigger on the jets i lose about 20 miles of range.
    I have the CVP emulsion tube, the CVP needle jet, EZ mixture screw about 2 turns out.

    I am running the stock rubber breather pipes that run back into the inlet manifold. Some say to modify this on the XLforum.

    So my question is what, if any, shim should i be running?

    Please see XLforum Sportster Motorcycle Air intake, Carburetor, EFI, Fuel, and Exhaust

    I am Loony on there just posted the same question but with pics.

    Thanks
  2. hotroadking

    hotroadking Super Moderator Staff Member

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    Well, I'd say your friends tip isn't working out, remove the shims, if the carb farts disapear then leave them out, that trick brings the needle up quicker, if the bike was running good before then leave the carb as it was.

    On these shorty pipes, do they have baffles? If not that will fix your low and
    mid range, open drag style pipes are made for 1/4 mile and making neighbors
    hate you when you go to work in the morning. Or comeing back from a bar at 2 am.
    ;)
  3. kenfuzed

    kenfuzed Administrator Staff Member

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    Sorry, seeing this late.
    First, do NOT shim the needle. This will do nothing for a hesitation (carb fart) problem. Adjusting the EZ-Just out an extra 1/8th turn will likely cure the hesitation... that is if the passages are not clogged which you'll never be able to adjust around. Also remove any spacer that the previous needle used, unless you are trying to run this on a DynoJet ThunderSlide... in which case you will be hard pressed to tune it correctly. On a stock slide with a CVP needle, no shims or spacers.

    Like HRK mentions, drag pipes are for sound and on a driver you'll always be battling to find any performance on the low end. If you can't baffle them, there is a trick to add a large washer on a bolt (think butterfly valve) in the path of the pipe where a baffle would normally go.

    Did I mention No Shims? ;)
  4. hotroadking

    hotroadking Super Moderator Staff Member

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    Those used to be called Lolly Pops a trick to fix the full flowing
    drag pipes and not put baffles in them, which IMHO is the right
    way to do it, and just FYI, other than the guy on the bike with
    the unbaffled straight exhaust, EVERYONE hates the sound
    as it kills their ears.

    http://www.nightrider.com/biketech/exhaust.htm

    [​IMG]
  5. Loony

    Loony New Member

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    When i say carb fart, it is an occasional pop now and then under low speed acceleration, could be anything.

    I agree with no baffles. I am running a spacer with 38??mm hole in a 48mm ID pipe? (cant remember exactly)

    anyway sounds much better and does help with performance compared to completely open pipes.

    It is actually quite reserved at tick over and i don't ride at 2am, I am neighbour aware of my actions. However car drivers can get $%%^£. My short pipes are actually quieter than full stock system with screamin eagle slips.

    I also have torque cones up top and cant really tell now its been so long changing this and that.

    ok, no shims are being run. Just wanted to be crystal clear on that.

    The bike performs well enough for what i want it for after all its an old harley and i should know better by now than to charge about like a maniac.


    Thanks for the replys
    Last edited: Apr 28, 2018

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