Discussion in 'Norton Commando Motorcycles (Classic)' started by maylar, Aug 11, 2019.
Why does the rear chain on my 74 850 get tighter when I tighten down the right side axle?
Check the wheel alignment and correct if required, the axle should in theory be perpendicular to the swingarm when tightened and not twist the rear wheel. In practise with all the components between the 2 wheels and the scope within the tolerances and the use of iso's the chances of the wheels being in alignment and the rear axle being perpendicular to the swingarm are slim so leave some extra slack in the chain so you get the right slack when the axle is tight. My axle wants to leave a 1/4" gap to the chain adjuster on the speedo gearbox side as it tightened so I have to push on the tyre as I do the last turn of the axle. Bike steers straight hands off and wheels are aligned so I have done nothing to fix the issue.
When tightening the RHS axle through bolt, use a big rag to trap the sprocket and chain in the lower side of the chain and roll the rear wheel forward so the rag jams in tight. This will have a tendency to roll the RHS axle bolt forward to the correct postion up against the axle adjustment bolt (need to be in the same position on both sides)
Keep the pressure on the rear wheel when tightening.
You could also make sure the swing arm flanges are flat and parallel to the centre line, and each other. I had a problem with mine that I cured by truing those flanges. Leave one side loose and tighten the other. If the adjusters are set exactly the same , the axle nuts should both touch the adjusters. Test again by doing the other side. Forcing the axle nuts against the adjusters is simply bending the axle [ isn't it ]. Your call.
Re alignment, I have:
1. 'Precisely' aligned motorcycle rear wheels (at a shop that did that with the 'latest' technology)
2. Have 'aligned' using a rough eyeball estimate ("looks straight to me!") and,
3. 'aligned by measuring the axle location from the end of the swing arm (or used the markings on the SA) and ensured both sides were the same measurement.
TBH, I have never noticed any difference in the way a bike acts regardless of how well (or poorly) I aligned it...
Dereck, the rag trick has no chance of bending an axle, the left side nut that retains the brake drum and sprocket assembly should always be tightened prior to tightening the RHS axle bolt shouldnt it?
Yes. On the center stand spin the rear wheel and jam on the rear brake before tightening. This supposedly keeps the brake shoes centered in the drum.
You may have misread my comment. If your axle is straight, and the stub axle has been made true, then it would not matter which side you tightened first when checking for warpage on each swing arm flange. If you tighten one side and it causes the other side to move away from the adjuster bolt, and vice versa, then surely it could mean those flange are warped like I found with mine. You should not have to force one side to line up if all is true. Putting the rear brake on to centralize the rear brake is a given but doing that wont counteract a bent flange.
An aside here though. How many people do the mounting nut up tight on the rear brake pivot? By doing so, it eliminates any self balancing or centralizing of thepivot between the shoes. [ just a theory I have and its the auto engineer in me asking ]