Chain Guard Alignment '74 850

RoadScholar

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The alignment of the 2 final drive sprockets should be the prime consideration; this can be checked with a string or any number of laser projection tools which are inexpensive and readily available or suitable straight edge types of stock. You do not have to install the wheel, but if not you will need sufficient spacers to simulate the width of the hub, speedo drive, yada, yada.

When you are satisfied with the sprocket alignment you can install the chain guard and see how much clearance you have with the rear sprocket. If you find it too far off center you can, as Concours mentioned, do some bending which can be very satisfying especially if you don't ruin the guard. I have found that there is some wiggle room to be had by tweaking the front guard fixing bolt with the oiler/spacer fastener slack. If the guard is tight to the chain run to the right a washer/spacer can be placed between the shock mount and the "slotted cage" the rear guard mounting bolt slips into. If you use this solution be sure to use, and shape, a larger enough washer/shim to give the "slotted cage" sufficient contact/support such that it doesn't vibrate and tear.

Best.
 

Saber

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The alignment of the 2 final drive sprockets should be the prime consideration; this can be checked with a string or any number of laser projection tools which are inexpensive and readily available or suitable straight edge types of stock. You do not have to install the wheel, but if not you will need sufficient spacers to simulate the width of the hub, speedo drive, yada, yada.

When you are satisfied with the sprocket alignment you can install the chain guard and see how much clearance you have with the rear sprocket. If you find it too far off center you can, as Concours mentioned, do some bending which can be very satisfying especially if you don't ruin the guard. I have found that there is some wiggle room to be had by tweaking the front guard fixing bolt with the oiler/spacer fastener slack. If the guard is tight to the chain run to the right a washer/spacer can be placed between the shock mount and the "slotted cage" the rear guard mounting bolt slips into. If you use this solution be sure to use, and shape, a larger enough washer/shim to give the "slotted cage" sufficient contact/support such that it doesn't vibrate and tear.

Best.
Thanks Bill. This sounds like the right approach. Get the sprockets aligned first as that is the most critical item. Then figue out a way to get the chain guard clearance without moving the sprockets. Any good tips tools or methods for checking the alignment of the sprockets?
 

myron1950

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Observations on chainguard, original (1974 Roadster) compared to AN replacement.
  • As mentioned before, gage of material on AN is lighter. I didn’t measure as my original has been powder coated. Consequently, it appears to be more compliant – not a problem as fastening locks it done pretty well.
  • Profiles are different. Minor differences.
  • Eyeball averaging of the width it appears the original is wider and would provide more clearance.
  • The width of the shock attachment is slightly larger on the AN chainguard – but both accommodate the 3/8-24 UNF Grade 8 Hex fasteners that I used for shock attachment.
  • Before I had original part PC I welded attachment nuts on the back side to make attachment easier.

  • Chaingurad 2.JPG
    Chainguard 3.JPG
 

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RoadScholar

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Any good tips tools or methods for checking the alignment of the sprockets?
String can work or you can purchase a laser projection tool at Home Depot/Lowes/on-line, they are very inexpensive, just don't let the beam hit anyone's eye(s).

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I just rebuilt the rear drum on my 74 and disassembled one on the rear of my 1970. Although they are slightly different, the 70 drum had a shim which in effect moved the drum ever so slightly. this could be the issue if you included a shim during reassembly. I admire your courage in assembling a Norton without ever previously doing so, or even owning one in the past! One other thing, the sprocket/drum assembly part number for a 1970 versus that for a 74 are different. Maybe the prior owner swapped out sprocket/drum not realizing (and they have different dimensions)? Jim
 

L.A.B.

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One other thing, the sprocket/drum assembly part number for a 1970 versus that for a 74 are different. Maybe the prior owner swapped out sprocket/drum not realizing (and they have different dimensions)?
Unlikely I would think as not only is the pre-71 a bolt-up drum with a different dummy axle assembly but because the 71-on drum assembly includes a (double-row) ball bearing and the pre-'71 doesn't.
 
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