Another Throttle Cable Replacement

Last week, I had yet another throttle cable breakage. Luckily, I've got two cables going to my carburetor, so I was able to get home. But I don't like riding with just one good throttle cable. I wasn't sure how long I could ride like that, and the good cable seemed to get a little too loose. That left me taking the van to work for a couple of days. 

With my first breakage a while back, I replaced the inner cable with 1/16 wire rope from Home Depot keeping the same cable housing. For this, I created a mold from pieces of aluminum flat stock for the carburetor end barrel fitting, and did what this guy did, more or less: https://www.youtube.com/watch?v=PV3XLAG3jx8. Additionally, I soldered a small bead on the control end to act as a cable stop to fit inside the ferrule. 

Later on, the control end of the cable broke. I had trouble soldering on another bead, since my silver-soldering skills kinda suck, so I just welded a bead of RG45 on the end. This seemed to work quite well, but I didn't think about the lack of corrosion resistance. I think this may have lead to last week's cable break, which happened right below where I welded on the end of the cable. I bet I burned off the zinc coating from the wire rope right below the weld, allowing it to corrode.

Without enough length left for a repair, I replaced the inner cable with some more wire rope from Home Depot, but I did things a bit differently this time.

To start with, I decided that instead of trying to fool with another molded solder barrel fitting for the carburetor end, I decided to just use a piece of 1/4" rod. I was initially going to use steel, but I worried about rust and wear. Luckily, I found some 1/4" zinc rod at the local Tractor Supply store. Using Zinc should take care of corrosion, and I can use grease to deal with wear.

After grinding a small flat spot on the side of the rod, I used my drill press to drill a 1/16" hole through the rod. Then, I used a larger bit (can't remember the size, sorry), to drill roughly half way through to provide space for a cable stop. I then cut the rod to approximately the length I needed.

Next, I brazed a bead of bronze on the end of the cable. After feeding the cable through barrel fitting, I compared the size of the bronze bead to the opening. I ground it down until it was about the right diameter, and lightly tapped it into the opening with a hammer. Next, with the bead tightly in place, I ground it down until more-or-less flush with the surface of the barrel fitting.

The assembled carburetor end of the cable already looked nicer than the old cable with the molded solder barrel fitting, but the new barrel fitting needed to be trimmed down a bit. Grinding with the grinding wheel on my drill press seemed too slow, so I used my angle grinder to speed things along. I did, however, use the grinding wheel to clean up the edge a bit.

After confirming that I could hook up the cable to the carburetor, I moved on to the control end of the cable.

I knew from past experience that feeding the cable through the metal portion of the cable housing with it's 90 degree turn was difficult and often lead to the cable end fraying. To prevent that, I brazed the end of the cable a bit. I still had quite a bit of difficulty getting it through. I tried a few different tricks without success, but finally had luck by welding a copper wire to the bronze coating on the cable end. (I say welding here, since I joined copper to copper-based alloy). Feeding the copper wire through the metal part of the housing was easy, though I did have to grind down the sides of the brazed end a bit to pull the cable through.

Once I did that, I cut away the copper wire. For whatever reason, I was having trouble getting a nice bronze bead on the control end, so I trimmed the bronze section off, and welded a bead of RG45 to the end. I then brazed over that for corrosion resistance.

With minimal cleanup, this fit into the ferrule quite easily. I did do just a tad bit of grinding to shape the brazed-over bead flush with the surface of the ferrule. Then, it was a simple matter to install on the throttle control. After making a few adjustments, I took the bike for a test ride and could not find any problems.

Hopefully, this holds up better than the last cable. After looking back at the pictures, I am concerned by what looks to be some unprotected cable below the bronzed bead cable stop on the carburetor end. Hopefully, just keeping both ends of the cable properly greased will prevent any corrosion. Time will tell.