Paula
Member
Clutch Arm
The clutch arm was broken when I purchased this bike. The casting had fractured where the clutch cable attaches to the end of the arm:
A previous owner had jury-rigged the setup so it would work, but I still wanted to replace the arm for the purposes of this restoration. My first thought was to fabricate one from steel bar stock (since I enjoy that kind of work), but before I got around to it, an alternative presented itself. I was talking to Chuck Gatto, and he mentioned that he was making up some repro clutch arms for sale, and had had some castings made and machined. I happened to mention that I was considering fabricating a new clutch arm for my engine. Not long after, I received a package in the mail with an unmachined clutch arm casting, along with a note: "Hi Paula, This one is on me. Have fun!, Chuck."
So, thanks to Chuck, I would be able to make a new clutch arm, just like an original! Here's a picture showing the original broken arm next to the new casting I was given:
The machining of the clutch arm casting is fairly straightforward. With the casting mounted "pulley" side up, the hole for the pivot pin is drilled and reamed, the larger boss is faced, and the 1/2-13 hole for the pulley bolt is drilled and tapped:
The casting is then inverted in the vise so that the pivot pin boss (where the arm rides against the crankcase) can be faced:
Next, the arm is positioned with the top side up. A 17/64 hole is drilled to a depth of about 3/4". Then, a 9/64" hole is drilled through the arm:
Lastly, a 1/16" wide slitting saw is used to slit through to the center of the drilled end of the arm. Also, a 1/4-20 hole is drilled and tapped for attaching the spring anchor:
The pivot pin was made from a piece of 1/2" dia. drill rod. One end of the pin was tapped 5/16-18 for the retainer bolt. The finished pin was pressed into place. After smoothing up the casting a bit, a couple coats of primer were applied. Here's the finished arm after painting, ready for duty:
Paula
The clutch arm was broken when I purchased this bike. The casting had fractured where the clutch cable attaches to the end of the arm:
A previous owner had jury-rigged the setup so it would work, but I still wanted to replace the arm for the purposes of this restoration. My first thought was to fabricate one from steel bar stock (since I enjoy that kind of work), but before I got around to it, an alternative presented itself. I was talking to Chuck Gatto, and he mentioned that he was making up some repro clutch arms for sale, and had had some castings made and machined. I happened to mention that I was considering fabricating a new clutch arm for my engine. Not long after, I received a package in the mail with an unmachined clutch arm casting, along with a note: "Hi Paula, This one is on me. Have fun!, Chuck."
So, thanks to Chuck, I would be able to make a new clutch arm, just like an original! Here's a picture showing the original broken arm next to the new casting I was given:
The machining of the clutch arm casting is fairly straightforward. With the casting mounted "pulley" side up, the hole for the pivot pin is drilled and reamed, the larger boss is faced, and the 1/2-13 hole for the pulley bolt is drilled and tapped:
The casting is then inverted in the vise so that the pivot pin boss (where the arm rides against the crankcase) can be faced:
Next, the arm is positioned with the top side up. A 17/64 hole is drilled to a depth of about 3/4". Then, a 9/64" hole is drilled through the arm:
Lastly, a 1/16" wide slitting saw is used to slit through to the center of the drilled end of the arm. Also, a 1/4-20 hole is drilled and tapped for attaching the spring anchor:
The pivot pin was made from a piece of 1/2" dia. drill rod. One end of the pin was tapped 5/16-18 for the retainer bolt. The finished pin was pressed into place. After smoothing up the casting a bit, a couple coats of primer were applied. Here's the finished arm after painting, ready for duty:
Paula