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My chopper speedometer always read about 10% fast. It's not a shovelhead, but the drive is the same, so I figured people would like to see what I did to correct it.
I pulled the wheel and the drive is marked 67120-84B, which is 2240:60 ratio, left side drive. The speedometer is marked 2.0, so the parts weren't matched. I found a left side drive that had a 2:1 ratio, 67127-84A, from 80's XL and FXR models. The problem is mine was 1.450" wide and the new one is 0.925" wide. I couldn't just add a 0.525" spacer, because the backs of the housings are different, mine has a raised center, and the new one hit the fork lower.
I read that people have changed the guts, but couldn't find any description or video of the process, so I tore into it, starting with the new one. First I took out the clip holding the flat drive plate, but it wasn't enough to take it off, the tabs were in a groove. I cleaned it off really well and put on my reading glasses, and discovered the wheel spacer was lightly pressed onto the housing. I'll clean up the pliers marks later.
After that, I removed the flat plate and this rubber seal:
Still couldn't remove the gear, because it is held in place by a metal ring pressed into the housing. I had to drill a small hole in the ring and pry it out. I'll straighten it out and seal the hole with Ultra Black rtv.
After that the it was easy to remove the drive gear and the shim below it.
Next I repeated the process on the original drive. The spacer is wider, and it would have been nice to just press it onto the other drive, but it isn't long enough to make up for the boss on the back of the housing.
I was hoping to just use the new drive gear, but the pitch of the work gear is different, and they didn't mesh smoothly. So I had to remove the worm gear too. I took out the tiny setscrew, but it was pressed in very tightly. So I threaded a 1/4-20 screw in where the cable goes, and pulled it out.
Putting it back together was straight forward. Just make sure to line up the hole for the setscrew before pressing in the worm gear housing.
Both are back together, but with opposite gearing.
I put the chopper back together but it got dark and cold so I'll test drive it another time. I did spin the wheel and the speedometer moved, so that's encouraging
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Speedometer Drive Rebuild
