Frame alignment. Gearbox sprocket and rear wheel sprocket

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I had a similar problem turned out my sleeve gear bearing had moved into the trans some, the fit was gone and the rear chain kept the alignment from machining things . When I rebuilt another trans with the sleeve gear in the proper place the chain would no longer align and the sprocket retaining nut rubbed on the inner primary . Turned out I had been running a pre commando front sprocket for years ( they have a different offset and are thicker) , causing the sleeve gear to move.
Frame alignment. Gearbox sprocket and rear wheel sprocket
Frame alignment. Gearbox sprocket and rear wheel sprocket
Frame alignment. Gearbox sprocket and rear wheel sprocket
Frame alignment. Gearbox sprocket and rear wheel sprocket
 
jimbo said:
I had a similar problem turned out my sleeve gear bearing had moved into the trans some, the fit was gone and the rear chain kept the alignment from machining things . When I rebuilt another trans with the sleeve gear in the proper place the chain would no longer align and the sprocket retaining nut rubbed on the inner primary . Turned out I had been running a pre commando front sprocket for years ( they have a different offset and are thicker) , causing the sleeve gear to move.
View attachment 13354 View attachment 13355 . View attachment 13356 View attachment 13357
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This is an interesting chain of thought. The gearbox has just been rebuilt and my mind was going to a possible main shaft sprocket issue. I shall certainly check this out
 
This is a link I have bookmarked from when I did my resto mod. Dont know if you have seen it or if it helps?

I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:-

  • The frame is symmetrical
  • The engine/gearbox cradle is offset 1/8" to the left.
  • The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame
I then installed the rear wheel:-

  • The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre
  • The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate
With the stock Dunlop rim, if you sight across the rim on the brake drum side you will see about 1/16" of hub when it's in the right place. In my opinion, front and rear adjusters should be on the same side. Otherwise as things wear and you take up the slop you angle the engine and gearbox in the frame. Since the swinging arm mounts to the cradle, a little one way in the front and a bit the other way in the back and the rear wheel is out of line considerably. The chain will still line up but the wheels will not.

https://www.nortonownersclub.org/support/technical-support-commando/wheel-offsets
 
gortnipper said:
This is a link I have bookmarked from when I did my resto mod. Dont know if you have seen it or if it helps?

I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:-

  • The frame is symmetrical
  • The engine/gearbox cradle is offset 1/8" to the left.
  • The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame
I then installed the rear wheel:-

  • The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre
  • The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate
With the stock Dunlop rim, if you sight across the rim on the brake drum side you will see about 1/16" of hub when it's in the right place. In my opinion, front and rear adjusters should be on the same side. Otherwise as things wear and you take up the slop you angle the engine and gearbox in the frame. Since the swinging arm mounts to the cradle, a little one way in the front and a bit the other way in the back and the rear wheel is out of line considerably. The chain will still line up but the wheels will not.

https://www.nortonownersclub.org/support/technical-support-commando/wheel-offsets
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Thanks for this. I’m going to do some more measuring when I get home. There are a few good ideas to check so far thanks
 
Not too long ago, prior to learning about the kegler clamps, I actually asked the members here if someone in the forum who lived nearby would take my bike for a test ride because I had checked everything and my bike still handled poorly. I was out of ideas since I inspected everything I could think of and had replaced my swingarm bushings which didn't help.

The discription of my handling in that thread was that the bike felt like it "snaked" down the road. On that thread, someone clued me into the flaw of the early model's swingarms of which I was unaware. Installing the kegler modification completely changed my bike's handling from "scarey" to "precise". The handling flaw was remedied by the kegler modification, and the result made "cause and effect" sense to me.

In my bike's case, the whole bike felt "rubbery", meaning it felt like it wiggled around and drifted around in the general direction where I pointed it. It did not inspire the desire to go faster... It makes sense that it was a worn swingarm tube because the sloppy interface matched the handling flaw.

SO,... If the bike feels rubbery and drifts around where you point it, I would think some worn out part is expressing it's "play" in the way the handling feels.

But,... If the bike feels rigid and doesn't wiggle around alot, but like it wants to go left as you say, I would suspect some critical misalignment (which is what you are persuing)

What to make of the combination of "pulling left" and "tank slapper" feel at speed,.. I would think a twisted headstock, which you are checking...
 
o0norton0o said:
Not too long ago, prior to learning about the kegler clamps, I actually asked the members here if someone in the forum who lived nearby would take my bike for a test ride because I had checked everything and my bike still handled poorly. I was out of ideas since I inspected everything I could think of and had replaced my swingarm bushings which didn't help.

The discription of my handling in that thread was that the bike felt like it "snaked" down the road. On that thread, someone clued me into the flaw of the early model's swingarms of which I was unaware. Installing the kegler modification completely changed my bike's handling from "scarey" to "precise". The handling flaw was remedied by the kegler modification, and the result made "cause and effect" sense to me.

In my bike's case, the whole bike felt "rubbery", meaning it felt like it wiggled around and drifted around in the general direction where I pointed it. It did not inspire the desire to go faster... It makes sense that it was a worn swingarm tube because the sloppy interface matched the handling flaw.

SO,... If the bike feels rubbery and drifts around where you point it, I would think some worn out part is expressing it's "play" in the way the handling feels.

But,... If the bike feels rigid and doesn't wiggle around alot, but like it wants to go left as you say, I would suspect some critical misalignment (which is what you are persuing)

What to make of the combination of "pulling left" and "tank slapper" feel at speed,.. I would think a twisted headstock, which you are checking...
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hi. The swinging arm spindle was slightly worn and been replaced. This is an August 74 Mk11 850 bike so shouldn’t have the older swinging arm.

the bike pulled left with the hands off the bars at low speed. Say below 30 mph.

The instability was in comparison to my Dommie featherbed race bike which was solid as a rock at 115 mph. You could have hit the bars with your hand and it would settle at any speed. The Commando in contrast started to feel nervous at about 80 mph.

The steering head has been checked by pulling the bearings and inserting a dummy rod and measuring head angle and alignment with the engine mounting studs isolastics and swinging arm.

I’m pretty certain the bike is dead straight now and think some of the suggestions about sprockets and gearbox mainshafts might be on the right track.

Basically the bike has had had a full frame check by a guy who builds his own frames and engine so I’m pretty sure he would pick up any steering head alignment issues

When I say builds the engines I means designs, makes the patterns, pours the castings, machined the castings makes his own cams crankshaft etc.

I thinking I may have a wrong offset gear box sprocket or a gearbox mainshsft issue as described by some of the guys above. I’m in Sydney right now but will check in a week when I’m home and report back
 
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I'm with swingarm issues on this one. They are welded up intentionally as "bent". This season a friend showed me one that was "corrected Straight" and I told him to toss it lest any new owner be unfortunate to get it at a future swap meet.
 
Torontonian said:
I'm with swingarm issues on this one. They are welded up intentionally as "bent". This season a friend showed me one that was "corrected Straight" and I told him to toss it lest any new owner be unfortunate to get it at a future swap meet.
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What exactly do you mean by welded intentionally bent please ?

Mine was twisted. If you ran a spindle through the swing arm pivot and mounted it on v blocks. Then putting the axle through with it mounted on v block then the axle was about 5 mm higher on one side than the other. The swinging arm would rock on the four v blocks. The axle and swing arm pivot were not parallel. This would mean if the swinging arm axis was parallel to the ground then the rear wheel would be leant over to one side.

Surely they didn’t weld them up intentionally so that the wheel leant over to one side !!!


If the bike was standing perfect straight with the front wheel vertical, the swinging arm pivot parallel to the ground then viewed from behind the rear wheel leaned over to the left side. This cannot be right ? They wouldn’t weld the wheel in leaning over surely
 
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jimbo said:
I had a similar problem turned out my sleeve gear bearing had moved into the trans some, the fit was gone and the rear chain kept the alignment from machining things . When I rebuilt another trans with the sleeve gear in the proper place the chain would no longer align and the sprocket retaining nut rubbed on the inner primary . Turned out I had been running a pre commando front sprocket for years ( they have a different offset and are thicker) , causing the sleeve gear to move.
View attachment 13354 View attachment 13355 View attachment 13356 View attachment 13357
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if it’s the sprocket on the left and the one in the last photo that’s the one I have got
 
johnm said:
What exactly do you mean by welded intentionally bent please ?

Mine was twisted. If you ran a spindle through the swing arm pivot and mounted it on v blocks. Then putting the axle through with it mounted on v block then the axle was about 5 mm higher on one side than the other. The swinging arm would rock on the four v blocks. The axle and swing arm pivot were not parallel. This would mean if the swinging arm axis was parallel to the ground then the rear wheel would be leant over to one side.

Surely they didn’t weld them up intentionally so that the wheel leant over to one side !!!


If the bike was standing perfect straight with the front wheel vertical, the swinging arm pivot parallel to the ground then viewed from behind the rear wheel leaned over to the left side. This cannot be right ? They wouldn’t weld the wheel in leaning over surely
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I have two spare MK3 swing arms here. Neither look to have had a hard life, but you never know. Mk3 swing arms look like they could be dropped onto concrete from a 30 storey building and remain unchanged.

I checked both for twist yesterday. With the pivot shaft level, the rear axle slots on both swing arms are 6 mm out of level. Both runout in the same direction.
This has me curious, I need to check the swing arm on the 850 to see if it's the same.
5-6 mm of twist here puts the wheel way out of line with things.

Glen
 
worntorn said:
I have two spare MK3 swing arms here. Neither look to have had a hard life, but you never know. Mk3 swing arms look like they could be dropped onto concrete from a 30 storey building and remain unchanged.

I checked both for twist yesterday. With the pivot shaft level, the rear axle slots on both swing arms are 6 mm out of level.
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Did you allow for the different slot widths as the RH slot is wider than the LH slot?
 
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