Page 2 of 2 FirstFirst 12
Results 11 to 14 of 14

Thread: Exhaust Leak Causing Misfire?

  1. #11
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    4,343

    Default

    I attempted to keep track of different spring collars for some time.

    It is my impression that the IDs were probably the same for all, even for Scheblers.
    If the collar does not slide easily when the choke is operated, the holes wear larger.
    Occasionally the needles will "hourglass" or have a flat side as well.

    The thicknesses of the collars vary however.
    In general, flathead models including Indians used a thinner collar, whereas postwar HD OHV's nearly always are found with thick collars.

    Too many exceptions to these rules cross my benches to declare any gospel.

    Since there is little height difference of the orifice hole for the two, I cannot imagine that there is a difference in air metering.

    Next quandry: Why are there differences in the lowspeed needle wells, if the collar does the metering? (The hole in the casting, as shown in the attachments.)
    And why do the last M74Bs with no serifs on the B have a needle well that is choked towards the bottom?
    Without L&L literature, we may never know.

    ....Cotten
    Attached Images Attached Images

  2. #12
    Join Date
    Jan 2008
    Posts
    133

    Default

    I come up with two sizes on the washer. 27345-27 is about .103 - .104" ID and 27345-41 is about .106 - .108" ID. A couple of thousandths make a big difference when coming off of idle.

  3. #13
    Join Date
    Jan 2008
    Posts
    133

    Default

    From the Harley manual-

    "CAUTION: The lift spring seat hole is calibrated and limits the amount of air bleed to idle circuit and must be in place; otherwise carburetor cannot be adjusted for satisfactory engine idling."

    .003" difference in the ID of the washer adds about 30% more air to the low speed circuit.

  4. #14
    Join Date
    Jan 2008
    Posts
    133

    Default

    Cotten,

    I may have found a partial answer to your quandry about the differences in the M74-B castings. I was trying to identify this carburetor, which someone destroyed by buffing it to death, and I noticed there is no hole for an idle enrichment lever. The idle mixture needle threads directly into the casting, and there is a separate idle bleed orifice threaded into the boss on the side. i don't have any literature for this carb, but I'm guessing it's an M53 off a K model. This would explain the additional material cast into the later bodies. Can anyone help?
    Attached Images Attached Images

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •