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After all these years, occasionally I hit a problem that seems so easy to solve, but then defies all logic. After MANY years of restoration and tweaking, I'm ready to put a few miles on my '47 FL. I have the rear wheel off of the ground and noticed that the chain has a very tight spot and a very loose spot. This is not abnormal for most chains and I've found it noticeable in new chains before they've 'stretched'. However, this difference in tightness is excessive (almost a full 1").
I first though that the transmission main shaft was bent, but I could not have imagined that I installed anything other than a new Andrews shaft. But, in the interest of a full-night's sleep I wanted to eliminate this horrible thought immediately. So, I removed the inner primary cover and indicated the shaft at the clutch hub nut location - about 0.001" (with running assembly run-out), so that's not the problem.
I marked the rear sprocket with a red wax pencil and noticed that the tight spot occurs at the same spot on the sprocket during each wheel revolution. Also, with the chain guard and primary side off, I can now see the chain tightening and loosening as the wheel is rotated. Obviously, the hub/drum assembly is running eccentrically on the rear axle. - OK, one step closer...
I changed the chain out with another new Diamond chain, just to check that off of the list. As I suspected, not the problem...
I next thought that the OEM rear hub may be the culprit - maybe a bend that I didn't catch when I rebuilt it (even though it trued up nicely - but hey, you never know!). I switched it with a new aftermarket hub but that wasn't it - same problem. So my next focus is on the drum/sprocket. The drum is OEM with a V-Twin replacement sprocket. I switched the drum/sprocket with a repro. assembly from V-twin that I used to originally mach-up the machine. Same problem.
I'm thinking that the only common denominators are the rear sprockets, as both are from the same source, one on my OEM drum and one on the reproduction drum assembly. Possibly they are eccentrically machined, but it would be unfair to disparage the source until I'm absolutely sure. One would think that given the number of replacement sprockets out there from this source, this problem would be well-known by now and probably corrected. So I'm not being too quick to pass judgement on the replacement part at this point. I do have another OEM drum with a worn sprocket in my storage container that I'm going to locate today and give it another try. If that doesn't work, I'm stumped.
Has anyone experienced this problem?
I first though that the transmission main shaft was bent, but I could not have imagined that I installed anything other than a new Andrews shaft. But, in the interest of a full-night's sleep I wanted to eliminate this horrible thought immediately. So, I removed the inner primary cover and indicated the shaft at the clutch hub nut location - about 0.001" (with running assembly run-out), so that's not the problem.
I marked the rear sprocket with a red wax pencil and noticed that the tight spot occurs at the same spot on the sprocket during each wheel revolution. Also, with the chain guard and primary side off, I can now see the chain tightening and loosening as the wheel is rotated. Obviously, the hub/drum assembly is running eccentrically on the rear axle. - OK, one step closer...
I changed the chain out with another new Diamond chain, just to check that off of the list. As I suspected, not the problem...
I next thought that the OEM rear hub may be the culprit - maybe a bend that I didn't catch when I rebuilt it (even though it trued up nicely - but hey, you never know!). I switched it with a new aftermarket hub but that wasn't it - same problem. So my next focus is on the drum/sprocket. The drum is OEM with a V-Twin replacement sprocket. I switched the drum/sprocket with a repro. assembly from V-twin that I used to originally mach-up the machine. Same problem.
I'm thinking that the only common denominators are the rear sprockets, as both are from the same source, one on my OEM drum and one on the reproduction drum assembly. Possibly they are eccentrically machined, but it would be unfair to disparage the source until I'm absolutely sure. One would think that given the number of replacement sprockets out there from this source, this problem would be well-known by now and probably corrected. So I'm not being too quick to pass judgement on the replacement part at this point. I do have another OEM drum with a worn sprocket in my storage container that I'm going to locate today and give it another try. If that doesn't work, I'm stumped.
Has anyone experienced this problem?
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