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Thread: Stroker Flywheels

  1. #1
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    Default Stroker Flywheels

    I have an old set of Sportster S&S flywheels. I love these wheels - they're the first series that S&S sold up to around 1970 or so with the markings on the outside faces and not on the rims as they were in the later 1970's.

    These wheels are marked 400-6 on their outside faces, below the pinion/sprocket shaft holes, and from what I can tell they're 4-1/4" stroke. However, because I don't want to remove the shafts (original and in perfect condition), I can't get an exact distance reading from pinion hole to crank-pin hole center lines with my calipers. Does anyone have the old S&S information sheets that describe which stroke is associated with the 400-6 part No.?
    Bill Pedalino
    Huntington, New York
    AMCA 6755

  2. #2
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    Put them in a truing stand or lathe, raise the rod (either one) as high as it will go. Measure to the top of the piston pin casting (end of the rod, not the hole) to the face of the flywheel, rotate all the way down, repeat the measurement and subtract the shorter from the longer and that is the stroke.
    Robbie Knight Amca #2736

  3. #3
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    Quote Originally Posted by Rubone View Post
    Put them in a truing stand or lathe, raise the rod (either one) as high as it will go. Measure to the top of the piston pin casting (end of the rod, not the hole) to the face of the flywheel, rotate all the way down, repeat the measurement and subtract the shorter from the longer and that is the stroke.
    Golly, Bill,..

    Eyeball center of main to center of crankpin, then just round it to the most likely fraction of an inch.

    (Times two is the stroke of course.)

    How many strokes would they make?

    ....Cotten
    Last edited by T. Cotten; 03-01-2020 at 03:47 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  4. #4
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    Quote Originally Posted by Rubone View Post
    Put them in a truing stand or lathe, raise the rod (either one) as high as it will go. Measure to the top of the piston pin casting (end of the rod, not the hole) to the face of the flywheel, rotate all the way down, repeat the measurement and subtract the shorter from the longer and that is the stroke.
    Robbie,
    Thanks Robbie. Yes, that's one way - but its only the wheels and shafts - no crank pin or rods and I'm too lazy to dig out a set of rods and bearings, so that's why I'm looking for the product sheet. I can also install a crank pin, place the wheel in the lathe, indicate from the crank pin surface ,spin it 180 degrees, measure to the surface again. Worst case, I'll make an effort.

    Cotten,

    As for the strokes thy made back then (and I'm going by memory)
    4-/1/4"
    4-1/2"
    4-9/16" Actually these were HD KHK Wheels - not S&S
    4-5/8" - Always my favorite stroke!
    4-3/4"
    5"
    I may be leaving one or two sizes out (I seem to remember 4-3/8" and 4-13/16", but not sure), but the most popular sizes for the street in my area back then were 4-1/2" and 4-5/8". I ran a 5" stroke Sportster with Dych cylinders for a short while when I was young but the pistons were very short and rattled a lot, the oil scrapers had to be built up (smaller diameter wheels), and the motor was simply too impractical for street use. I currently own two 4-5/8" bikes (1970 XLCH and 1979 FX). I built these motors decades ago and they both run very well.
    Last edited by Bill Pedalino; 03-02-2020 at 06:23 AM.
    Bill Pedalino
    Huntington, New York
    AMCA 6755

  5. #5
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    Chicago
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    [QUOTE=Bill Pedalino;188072]Robbie,
    Thanks Robbie. Yes, that's one way - but its only the wheels and shafts - no crank pin or rods and I'm too lazy to dig out a set of rods and bearings, so that's why I'm looking for the product sheet. I can also install a crank pin, place the wheel in the lathe, indicate from the crank pin surface ,spin it 180 degrees, measure to the surface again. Worst case, I'll make an effort.

    Cotten,

    As for the strokes thy made back then (and I'm going by memory)
    4-/1/4"
    4-1/2"
    4-9/16" Actually these were HD KHK Wheels - not S&S
    4-5/8" - Always my favorite stroke!
    4-3/4"
    5"
    I may be leaving one or two sizes out (I seem to remember 4-3/8" and 4-13/16", but not sure), but the most popular sizes for the street in my area back then were 4-1/2" and 4-5/8". I ran a 5" stroke Sportster with Dych cylinders for a short while when I was young but the pistons were very short and rattled a lot, the oil scrapers had to be built up (smaller diameter wheels), and the motor was simply too impractical for street use. I currently own two 4-5/8" bikes (1970 XLCH and 1979 FX). I built these motors decades ago and they both run very well.[/QUOTE


    -6 is 4-5/8. I just slipped a set of those wheels, circa 1970 and serial 16xx-6 in my 64CH. You can see photos for comparison in the member bike builds.

    Only thing to keep in mind is to not torque to later steel wheel specs ;-)

  6. #6
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    Bill; Try the S&S Tech line. 608-627-8324. This phone number is in an old 1993 S&S catalog that I have from when I was a dealer. I'm guessing that it is still good.
    Craig

  7. #7
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    Quote Originally Posted by 41craig View Post
    Bill; Try the S&S Tech line. 608-627-8324. This phone number is in an old 1993 S&S catalog that I have from when I was a dealer. I'm guessing that it is still good.
    Craig

    By the time you are done calling . . . you can look at these pictures and determine for yourself if what I wrote above is or is not true.

    Blow up the photos -- the serial number is clear on the bottom of the wheels in the following two photos.

    IMG_4496.jpg

    IMG_4498.jpg


    All of the early S&S flywheels carried matched numbers for the left and right wheels. These are the serial number and correspond to records about balancing, etc. The final part of the number is the stroke code.

    In Bill's case it is 400-6 and in the flywheels pictured above it is 1609-6. The confusion here is that Bill stated "part number" and that isn't what his "400-6" refers to here.


    The part with the - followed by a number is the stroke code. As stated in my reply: -6 equals 4-5/8 whether they are the cast wheels or the forged wheels.


    You can find copies of the stroke code table all over the internet. S&S stayed with the same codes from the late 60s onwards. Here's the same info from S&S's website -- ignore that they say -6 is for 77-81 ironheads . . . if you look at older tables it is all the same. And, even if these were Big Twin -- they also use -6 for 4-5/8

    https://www.sscycle.com/tech-info/tech-tips/lower-end


    If you need more "proof" that -6 really are 4-5/8 wheels; here is a photo of stock length cylinders (5.330) being mocked up with S&S 1000cc Ironhead stroker pistons for a 4-5/8 stroke. Notice the piston just comes up to the Head Gasket Surface at TDC without base gaskets? That is exactly where it should be for 4-5/8.

    IMG_4472.jpg

    IMG_4475.jpg

    These photos are from my own bike and I just buttoned up the bottom end a few weeks ago. You can see the whole saga over on the Members Build section of the AMCA forum. I like strokers . . .and stroker parts.

  8. #8
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    Quote Originally Posted by chuckthebeatertruck View Post
    By the time you are done calling . . . you can look at these pictures and determine for yourself if what I wrote above is or is not true.

    Blow up the photos -- the serial number is clear on the bottom of the wheels in the following two photos.

    IMG_4496.jpg

    IMG_4498.jpg


    All of the early S&S flywheels carried matched numbers for the left and right wheels. These are the serial number and correspond to records about balancing, etc. The final part of the number is the stroke code.

    In Bill's case it is 400-6 and in the flywheels pictured above it is 1609-6. The confusion here is that Bill stated "part number" and that isn't what his "400-6" refers to here.


    The part with the - followed by a number is the stroke code. As stated in my reply: -6 equals 4-5/8 whether they are the cast wheels or the forged wheels.


    You can find copies of the stroke code table all over the internet. S&S stayed with the same codes from the late 60s onwards. Here's the same info from S&S's website -- ignore that they say -6 is for 77-81 ironheads . . . if you look at older tables it is all the same. And, even if these were Big Twin -- they also use -6 for 4-5/8

    https://www.sscycle.com/tech-info/tech-tips/lower-end


    If you need more "proof" that -6 really are 4-5/8 wheels; here is a photo of stock length cylinders (5.330) being mocked up with S&S 1000cc Ironhead stroker pistons for a 4-5/8 stroke. Notice the piston just comes up to the Head Gasket Surface at TDC without base gaskets? That is exactly where it should be for 4-5/8.

    IMG_4472.jpg

    IMG_4475.jpg

    These photos are from my own bike and I just buttoned up the bottom end a few weeks ago. You can see the whole saga over on the Members Build section of the AMCA forum. I like strokers . . .and stroker parts.
    CHuck,
    Thanks for the information. The wheels I have are earlier than the ones with the codes on the rim. But your information about the -6 is exactly what I'm looking for without doing any measuring work myself.
    By the way, that ring on the 1st gear shoulder really brings me back!
    Thanks so much....
    Bill Pedalino
    Huntington, New York
    AMCA 6755

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