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Thread: Another way to fix a stripped drive shaft filler plug

  1. #1
    Registered User Anyname's Avatar
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    Another way to fix a stripped drive shaft filler plug

    So there I was, standing in my motorcycle shed, a 14MM tap in one hand and a new 14X1.5MM filler plug in the other. I was staring at the stripped drive shaft filler plug hole on my 1986 R80 and realizing that the only way that a 14 MM tap was going to re-thread that hole was if I pulled the final drive and reamed the hole first. It was also looking likely that I would either have to dismantle the final drive unit itself or grind the taper off of the tap to provide enough full threads for the new plug.

    Phooey. That's a lot of work just so that the R80 wouldn't have a rubber cork for a filler plug. It also seemed possible that bad things could happen to a perfectly good final drive during that much surgery.

    I took a second look at the filler hole and realized that while it looked to be stripped smooth, it still had some residual threads, especially near the bottom where the previous owner and BMW's 12 MM filler plug couldn't reach. A quick trip to the hardware store for some metric taps and dies, and I formulated a plan to sleeve the hole which a hollow plug threaded 12X1.5MM on the outside and 10X1.5MM on the inside. The standard 10X1.5 bolt stocked by my hardware even had a smooth raised lip for the gasket to seat on.

    This is what I came up with, sorry for the crappy photo, but it's hand held in poor light without a flash. Glare from my flash unit made the part unrecognizable. This is the sleeve and the new plug:
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    Last edited by Anyname; 11-07-2010 at 01:12 AM.
    BMW R bike rider, horizontally opposed to everything...

  2. #2
    Registered User Anyname's Avatar
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    Here is the sleeve threaded and epoxied into place. The 12MM threads I machined on the exterior of the sleeve had a better thread form than the original BMW plug and were not tapered at the end, so they actually gripped fairly well. I used the new plug to drive the sleeve into the filler hole. As you can see, I didn't remove any parts from the bike to install the sleeve. I did wax the filler plug to make sure that the epoxy didn't adhere to it and I only put epoxy on the threads near the shoulder of the sleeve. I didn't want epoxy in the swing arm.
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    BMW R bike rider, horizontally opposed to everything...

  3. #3
    Registered User Anyname's Avatar
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    This is the sleeve with the new 10X1.5 filler plug installed. I found that BMW sells 10MM aluminum filler plug gaskets. I have a pile of them left over from the fluids servicing kits I used to get with my K100.
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    BMW R bike rider, horizontally opposed to everything...

  4. #4
    Registered User Anyname's Avatar
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    This is the new filler plug, since the sleeve extends about 2/10ths of an inch above the casting, the new plug can have much longer threaded section than the original and should be less likely to strip the hole. I stamped 10X1.5 on the top of the plug so that the next owner will have a clue as to what the thread size is. So far the only down side I can see is that I now have to fill the drive shaft with fluid through a smaller hole. Since I have acquired a collection of turkey basters, cake decorators, ketchup dispensers and plastic syringes for squirting lubricants into difficult to access reservoirs on BMWs, that shouldn't be a major problem. The drive shaft only holds 150ML.
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    BMW R bike rider, horizontally opposed to everything...

  5. #5
    Bill Burke
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    Quite elegant. I like it. Certainly more elegant than my bodge job with a helicoil.

  6. #6
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    Good Job !

    I've certainly been 'surprised' by finding much less carefully done repair jobs before - I wouldn't be too worried about that one.
    BMWs in my garage: 1982 R65LS, 1978 R100/7

  7. #7
    Registered User ebeeby's Avatar
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    Nicely done!

    I have a feeling that Moe, Larry and Curly await the numbnuts who over-torque and strip these things. Some fingers in the eyes, hammer blows to the head, clumps of hair pulled out - for about 100 years - seems like a fitting purgatory.
    1973 R75/5

  8. #8
    Rally Rat
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    Quote Originally Posted by ebeeby View Post
    Nicely done!

    I have a feeling that Moe, Larry and Curly await the numbnuts who over-torque and strip these things. Some fingers in the eyes, hammer blows to the head, clumps of hair pulled out - for about 100 years - seems like a fitting purgatory.
    I agree. In 35 years of working on these bikes, I have never stripped one of these drain plug threads. I've sure fixed a lot of them, though...

  9. #9
    Simpleman
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    Nice and thanks for sharing

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