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Henderson and Excelsior throttle cable danger!

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  • Henderson and Excelsior throttle cable danger!

    Some of you may have followed along on my thread about our Lindbergh ride this September on our Series 20 Excelsior's. If you did, you know one of our riders experienced a horrible crash, all due to a stuck throttle. I just posted an update on his condition as well as a detailed explanation of the throttle issue in hopes that others can avoid this issue. I'll repost the throttle cable issue here. Please share this with any X or Henderson owners you may know, it could save their life!

    This is a good time to elaborate on what caused Stewarts crash on day 5 of our ride. Hopefully others can learn from these details and avoid a similar disaster! Stewart is the second friend I know that had a similar situation that locked the throttle in a wide open position and resulted in a horrible crash. Doug Rollert learned this lesson years ago on his beautiful 23 Deluxe.

    This applies directly to all late teens-mid 28 Henderson and 20-mid 28 Excelsior machines but the general concept of tending the throttle cable applies to all motorcycles!

    The Schwinn design used an external throttle cable setup, meaning it was not fed through the hollow handlebar. The solid cable slid through a coiled wire housing. I believe this was referred to as the Bowden Cable, patented by a man by that name. Correct operation requires both ends of the coiled wire housing to be securely fastened at both ends at all times. If either end can move, throttle cable action is reduced, or lost all together. Schwinn used a big clamp on the handlebar cross bar to hold the housing in place and a series of small clips along the way to attach the housing to the frame. The wire cable was attached to the twisting tube on the handlebar with a small ball and socket, allowing a universal swivel if you will for alignment. This wire attachment also has a long threaded tube screwed on the end which slid over the wire casing to aid in alignment and protect the wire from dirt and damage. With the throttle fully closed, this tube should almost touch the clamp. Here is a closeup shot of the setup on my 24 X, this is in the fully closed position. Note the sliding tube is very close to the clamp:

    Throttle cable 1.jpg


    With the throttle fully open, the sliding tube still covers the casing, keeping things aligned and protected properly.

    Throttle cable at frame.jpg

    This is where the casing is attached to the frame neck. Hendersons are setup exactly the same up to this point. The only difference comes at the carburetor end which is less important.


    Here is the problem...... In Doug Rollert's case, he used a reproduction cable housing which was a smaller OD. While attempting a tight U turn on a side street, It allowed the cable to suddenly slide through the frame clip when the handlebars were turned all the way to the left. This pulled the throttle wide open and his foot slipped off the foot clutch and launched him into a parked truck. This sent him to the hospital for major surgery and bent the forks, fender, wheel and frame.

    In Stewarts case, the 2 screws on the handlebar clamp loosened up just enough to allow the casing to be pulled through, perhaps a little bit each time the throttle was opened quickly. As time went on, the distance between the clamp and the sliding tube increased. In addition, there may have been a slight misalignment in the location of the clamp, giving a slight curve to the housing. We suspect that as Stewart crested a steep hill in Kentucky with the throttle near wide open, he shut it off abruptly when the sharp curve appeared just after the crest. The excess cable suddenly bunched up and made a loop between the clamp and the sliding tube, locking the throttle in a near wide open position. The rest is history. Here are pictures of Stewarts setup after the crash. The casing could be slid through the clamp with little effort. Granted, the handlebars are busted off and bent, but the loop was clearly locked in place. All the other clamps were tight, so this had to be the culprit.

    Throttle cable kink 2.jpgThrottle cable kink 3.jpg

    You can see from the last picture there is way too much cable housing exposed between the end of the sliding tube and the clamp, allowing a nasty kink in the housing, locking the throttle open.

    So, CHECK YOUR CABLES!

    1. Be sure all the clamps are TIGHT and will hold the casing properly. Some reproduction casings are a smaller OD so the clamps must be modified to properly hold the casing!
    2. Be sure the sliding tube is as close to the handlebar clamp as possible with the throttle fully closed. Any excess housing showing is a recipe for disaster!
    3. Be sure the swivel joint and tube are aligned properly to allow the sliding tube to easily slide over the casing with perfect straight alignment. Simply rotating the handlebar clamp will do the trick.
    4. CHECK THE SCREWS REGULARLY to be sure they are TIGHT. Use loctite on them as well!

    You can be sure we examined our setups immediately after Hans discovered the cause of Stewarts crash!

    In theory, this applies to other machines as well. The cable housing must remain tight at all times, especially at the handlebar end!
    Attached Files

  • #2
    Gene -- thank you for sharing this. I actually just sent off an article to our chapter newsletter editor talking about making custom cables for unusual bikes for which no good replacements are available. I deeply enjoy making cables -- and making them work!

    Anyways, despite Bowden Cables (yes, you had the name correct) being around for a very long time -- many riders remain unfamiliar with them or how they actually work. EVERYTHING you describe is all too common -- and all too common with "modern" repo cables. Add in the unfamiliarity with the system (ie you can use the inner OR the outer to actuate!) and problems creep up fast. It's sorta like wiring -- basic wiring already scares most riders . . .full rewiring is simply a bridge too far.

    The truth is that control conduit (the outer casing) comes in several sizes. Most aftermarket companies choose 5mm or 5.5mm conduit for repo cables. This allows them to buy rolls of conduit cheaply and realize economy across many makes/models. BUT, a lot of American prewar bikes are 6mm conduit; with some even being 6.8mm where as European bikes were often 5 or 5.5mm! So, indeed, none of the clamps fit the chosen conduit from the supplier because they went with the most common conduit size post-war; not necessarily the "correct" conduit size for the bike in question. Maddening, but all too common. It usually is dealt with by shimming clamps with beer cans or what have you; but any slip can cause issues.

    The way to avoid all this is to make your own. Flanders is the best source in my opinion: http://www.flandersco.com/action.las...gory=CablePart

    It is dead simple to cut the vinyl casing off the conduit if you need the non-sheathed look.

    If you can solder -- you can make cables -- and make them better than the aftermarket stuff that isn't quite right.

    Comment


    • #3
      Great info Chuck! I'd be interested to see the article you sent to the local chapter newsletter, as would others I'm sure.

      I had a very nice repro cable and housing made by Tom Fickau which matched the OD of the original housing perfectly. I tried and tried but could not make the cable slide easily inside the housing. I hate cables that drag and are hard to move! So, I went with new stuff. I bought a roll from the local lawn mower shop. It has a black vinyl cover, easily removed, and a teflon lining which of course makes the inner wire smaller but it slides very nicely. This was a Howard Wagner trick I learned years ago. The OD was smaller indeed and knowing ahead of time the issue my friend Doug Rollert had on his Henderson, I minded the clamps very carefully, making sure they gripped the smaller housing correctly. This involved flattening them a bit and trimming a tiny bit off the tip end for the frame clips. The handlebar clamp needed a bit of work to widen the gap between the two flats, insuring the curved clamp area was gripping properly. I also shared this information with our group on Whats App as we worked through our restorations. Stewarts problem came from the handlebar clamp screws working loose, just a bit.......

      The issue I did have was that my throttle moved too easily believe it or not! I was trying to hold a steady speed at 45 mph. Once set, if I let go, the throttle would either open or close on it's own pretty quickly. It seemed like if I could set it with the butterfly exactly 1/2 open, it was balanced and would hold. Anything more, it would open up and accelerate. Anything less than half and it would close up and slow down. So, I had my hand on the throttle virtually all the time, which caused the only discomfort I experienced the entire trip, a sharp pain in my upper back. Other than that the X was a delight to ride all day long.

      Anyway, MIND YOUR CABLE CLAMPS!

      Comment


      • #4
        Gene, Just a thought but a couple of staked points ( outside divot, inside the point) on each cable clamp half where they contact the cable housing would help grab it instead of just the slick surface. I did that on all my Super X's. It helped. Done before the nickle was applied with a pointed punch over a curve buck. Rich P.S. some H-D cable clamps have a similar little tang.
        DrSprocket

        Comment


        • #5
          This is an excellent report and valuable information that all of us should be aware of. Thanks for posting it, Gene.

          When I was restoring my 1913 Henderson I puzzled about the proper way to connect the cable linkage at the carb end. What seemed correct meant that the twist grip turned the opposite way from what we'd expect. I could reposition the control arm on the Schebler H carb 180 degrees to rectify that but it didn't seem right. I've seen both setups on early Hendersons.

          In the end, I went with what seemed correct at the carb end and accepted the fact that my Henderson would have a "reverse" twist grip. What this means is that I close the throttle by pulling the Bowden cable in, thereby avoiding the "bunching up" problem described above. (It could possibly bunch up when opening the throttle, but the consequences are much less dire.) Could it be that this was the reason it was connected that way?

          For reference, I used this closeup from a picture of William Henderson's bike. You can see the carburetor control arm extending up toward the left side of the bike. This is the setup I used.

          1913 Henderson.jpg

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