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Thread: XLH transmission drain plug stripped

  1. #1

    Default XLH transmission drain plug stripped

    I bought a 1974 XLH recently that was leaking quite a bit of oil. I found that the transmission drain plug was stripped. So I ordered a Colony oversize plug (9/16"-18) and a tap for the same. I took out the battery, gas tank, and drained the fluids out so I could lay the bike on it's side to work on the retap. The problem I'm having is that the plug freewheels and doesn't come out. I've pulled and pried on it with vise grips and various pry bars with no luck. I'm sure I could bust the thread out of the case if I wanted to, but with the new oversize plug only being a 1/16" bigger than the original I'm trying to be careful. I could probably cut/drill the plug out, but there again I don't want to bugger up the hole in the case to where I can't retap it. Any ideas?

  2. #2
    Join Date
    Dec 2010
    Lamoille County, Vermont


    You also don't want a boatload of chips in the transmission...

    Lock the plug in a pair of vice-grips... If you need to, clamp the vice-grips onto the frame.

    That lets you work on the plug. If you drill across it with a small drill (1/8") make a line of holes. THe ones on the outside just cut through the hex. The ones in the middle cut through the actual threaded part. Then you may be able to collapse the plug and remove it.

    You can also drill the center and go with ever-increasing drill sizes until the middle is able to collapse.

    If you don't mind stripping the threads, drill the cap, tap it and thread in a bolt. Then remove with a slide hammer. BUT that puts the case at risk. You don't want to blow out the aluminum case.

    Your basic premise is to worry it out. Just keep removing stuff... picking, poking and cutting and, eventually, collapse it and remove. If you want to avoid getting chips into the transmission, keep your tools covered in a thick layer of axle grease. That will trap chips and keep them from floating around into the trans.

    If you over-cut the threads, you can use an Irontite aluminum tapered plug and re-drill/re-tap to standard (my preferred method) or (and I'm not a fan of these) a Helicoil insert that will restore the threads to standard.

    Congrats on a neat bike! My first HD (and vintage bike) was a '76 XLCH... and I have a soft spot for this era bike! Post some pix!



  3. #3
    Join Date
    Apr 2010


    i did that job this morning-not on it's side-that can let more chips in[flush with Kerosene]
    You have to use drill with 1/2" bit to get enough clearance to start the tap[don't worry about stripping the old threads more]
    I have the colony tap that i start the threads and another without the lead in to finish
    I have been in a few BT trannys that the fill plug was retapped and left a bunch of chips inside-seem to lay in the bottom and not cause issues[That's not the way I do it!]
    Use grease on drill bit and tap and bring out often to clean and regrease
    Last edited by duffeycycles; 08-19-2015 at 05:12 PM.

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