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Thread: GX Schebler info?

  1. #1
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    Default GX Schebler info?

    Any GX Model Schebler experts out there?

    Futile I know, but perhaps literature that might list manifold attachment, bore, venturies, or throttledisc angles?
    Or various idle bleeds, or various HS needles?

    Only a pure fool would attempt these tortured fossils; Any clues at all would be greatly appreciated!

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  2. #2
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    Hate to bring this back up Folks,..

    But I just received some of the worst replacement parts that have ever crossed my benches.

    (Yes,.. Even worse than Tedd's!)

    Not only was the reproduction float too light, but it was soldered on backwards.
    The whole batch of hardware was pathetic, too long to list, but the absolute worst was a buffed-shiney throttledisc that had a round and polished edge instead of beveled, chokedisc thickness far too narrow for a throttleshaft, and one screw hole was triangular. But it had a pretty stamp.

    Who wants to do GX Scheblers?

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  3. #3
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    Dear Tom, I've got two 1930 Harley C 500 cc single cylinder models to restore and a GX-1 and GX-4 Schebler to go with them. Yes they are pretty horrible, but the reprinted 1928 Schebler manual has a picture with a parts list, plus operating and maintenance instructions. Main problem of course is corrosion of the body, plus it's hard to find them anywhere near complete. As I find out helpful info I'll try to post it here.

  4. #4
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    Steve!

    The Service Station manual shows the GX-4, but the GX-1s on my bench have short chokeshafts with soldered-in discs, both of which I had to make. Cutting throttlediscs is routine, of course, but I found that only 11º will close in the middle of the idle bleeds, so the 9º discs are a mystery to me.
    Fortunately, I can get much of the critical hardware from Tom Fickau, but it looks like I'm about to start cutting needles. And considering how problematic this reproduction float is, I might as well figure out a way to cut something from foam, but weigh it down somehow.

    ....Cotten
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    Last edited by T. Cotten; 07-23-2016 at 07:52 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  5. #5
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    How do we fix this one, Folks?

    As you can see, this tortured GX-4 has both a damaged idle bleed hole in the body, and a damaged "one hole" idle bleed plug.

    Any sensible suggestions as to how to address this critical issue?
    Welding the thin wall of the body would be futile, as if I could find a TIGmeister who would risk it anyway.

    Can anyone give me accurate dimensions of the original end of the #1 plug and its body hole clearance?

    As always, many thanks in advance,

    ....Cotten
    PS: All two-hole DXs seem to have a #50 front hole and a #71 (or an odd #55 front hole for a Cleveland).
    So, if I calculate the surface area of those holes, and any gap between plug and body hole,... and try to approximate the 'divot' to a #50 with a plug that nearly seals to a cleaned up hole, and perhaps notched for the rear to ~#71.... think it will run?

    PPS: The GX-4 may be the only model that used the 9º disc? Why?

    PPS: Why does the "Service Station Manual" make the bodies appear black?
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    Last edited by T. Cotten; 09-30-2017 at 05:10 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  6. #6
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    Dear Tom, the GX-1 I have has the 11 degree throttle disc, soldered choke disc, and what looks like numbers 55 and 70 idle holes, same as the larger units, but hard to be exact because of corrosion of the body. Runs OK on a 500 cc 1930 Harley C single.

  7. #7
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    Thanks Steve!

    The Service Station manual calls the 11º "P-478", and the 9º "P-705".
    And lists the holes for your GX-1 at #50 and #71. Since your 'front' hole is smaller than "spec", it is hard to imagine it was altered, but it does imply that the size of the bleeds may not be life-or-death.
    It would have made me feel better if it was larger than spec, however, as my task is to somehow conjure this sick puppy close, at least.

    My concern is making the open area of the idle bleed approximate the original.
    Although the fuel to the idle bleed is metered by the needle, the orifices become the metering device for air to the main nozzle when the venturi kicks in, and the entire idle circuit reverses.
    Too large of a bleed would produce a lean mixture at cruising speeds, and the damage may do just that.

    I need more research before I do further surgery.
    It is confusing that this GX-4 has the "one-hole" bleed as pictured in the manual, rather than the two holes as spec'd in the listing.

    ....Cotten
    Last edited by T. Cotten; 10-01-2017 at 10:27 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  8. #8
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    Beyond all belief, Folks,...

    I found my old notes from a GX-2 that came in with a #1 "one hole" idle bleed.
    (Naturally, the Manual specs two holes for it as well. No model is spec'd for a #1 one-hole plug.)
    Amazingly, the hole in the body was #12 (.189"), and larger than the damaged hole in the GX-4. Perhaps the damage was from peening.
    The end of the undamaged #1 plug was .167"; subtracting the area of the plug from the body holes is a mere .00196 in².

    The combined areas of a #50 and #71 holes is .0044 in², nearly two and a half times larger.

    Flow through orifices is a complicated science, Folks.
    Two smaller orifices do not flow the same as one large one of the same 'area', much less one constricted like the plug/hole, but what can I do?
    If anyone out there is a genuine engineer with skills to direct me, please, please assist for the future conservators!

    My plan at this time is to dress the peened hole as close to spec as possible, and cut the plug's replacement tip a skosh oversize, if the hole does not clean
    completely.

    Any suggestions before I commit to raw intuition and luck?

    .....Cotten
    Last edited by T. Cotten; 10-01-2017 at 02:03 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  9. #9
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    This is the best I can do with it,

    .....Cotten
    PS: Now for the long anxious wait for it to get into service....
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    Last edited by T. Cotten; 10-02-2017 at 11:01 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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