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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!
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!
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