If you ride a motorcycle long distances, you have probably had a problem with numbness or cramps in your thumb or fingers from holding the throttle. This fall I rode from Raleigh, NC to the Blue Ridge Parkway on my relatively new Bonneville, and the only complaint for the whole three day weekend was "numb thumb". In the last post I mentioned the need for a throttle lock, or what should be called a throttle brake, as such a device is not intended to lock the throttle, but provide a finely adjustable brake to relieve the rider of the necessity of holding constant torque on the motorcycle throttle.A number of products are commercially available. I considered all of them. None of the local motorcycle dealers carried any of these. When ordering sight unseen from the internet, or on the basis of one photo, there is always the concern of improper fit and the need to return the product.
Some of the "universal" brakes were ugly and clumsy. Some were just too cheap. I tried one of these, and found it difficult bordering on dangerous to use. Some are really nice looking and exceedingly expensive. Then there is Kaoko, which is priced in the middle, but depends on an exposed set screw to tension the adjusting nut, which was subject to moving about as the throttle moved. That looked to me like a feature that would require constant fiddling. They're sort of expensive too.
So, I made one (two actually) myself. It turned out to be a simple and straightforward device. If you have a lathe, a mill or drill press, (and I assume you do) and a motorcycle, you can make one for your bike too.
Ok, enough talk, time for pictures. The first photo shows all the components. The threaded part at top left fits inside the handlebar end, and carries all the other parts. I'm going to call it the threaded carrier (clever, huh?).
The black plastic ring which I'm going to call a bushing, at bottom left is made of Delrin. It is one of the ways my design differs from the Kaoko throttle brake. I try to keep some Delrin rod and sheet in the materials bin because it is so useful, and easy to machine. It's also pretty cheap. The purpose of this part is to provide a smooth wear resistant surface for the adjusting nut and throttle grip end to work against, and to isolate the adjusting nut from throttle motion that might cause it to tighten or loosen unexpectedly. The notch in the ring fits around the brass pin pressed into the threaded carrier. This is what prevents the Delrin bushing from rotating, but allows it to slide sidewise when pushed by the adjusting nut.
There is a round recess bored in the threaded portion of the carrier. The little white Delrin button and spring fit this recess, and press against the underside of the adjusting nut, to keep it from slopping around. This eliminates the need for a setscrew in the adjusting nut, and is the second difference between my brake and the Kaoko brake.
The adjusting nut is just that. Twisting it clockwise viewed from the bar end causes it to press against the bushing, braking the throttle. Twisting it counter clockwise releases pressure on the bushing and throttle. The design for the adjusting nut was shamelessly ripped off from Steve Bedair's site. Thanks again to Steve.
This photo from the preceding post shows the brake installed on my bike. This was before I sanded and rounded the sharp edges, and blended the outside of the adjusting nut into the contours of the new bar end. The last photo shows the assembled brake, and the original bar end.
I spent some time this weekend riding and using my new brake. I had already tried out a really ugly prototype the weekend prior. The brake works really well, if you fight the tendency to over tighten it. Very light pressure on the throttle is sufficient to provide relief for your throttle hand and an end to numb thumb. The hidden tensioning button for the adjusting nut works as anticipated. I'm considering publishing plans for this brake. Of course, this design can be applied to other bikes, but dimensions would vary depending. I already have a request from a neighbor for one for his bike.



