1972 commando rebuild

BERT

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Hi everyone, I am a first time Norton owner and am in the midst of an almost total dismantling to get at some discovered issues that I feel should be addressed to keep this puppy rolling. I really appreciate the help so far through the Forum of the kind folks who share their knowledge with other Norton owners. These bikes are easy to love, not only looks and riding, but the wrenching involved keeping them going. So good luck to all who are putting in the time as I am. Dave.
 

grandpaul

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Hey, @BERT , make sure to post pix & narrative starting back from the beginning...

Thanx!
 

BERT

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Hey, @BERT , make sure to post pix & narrative starting back from the beginning...

Thanx!
Not too much to see right now, but a good opportunity to figure out how to post a picture. Here it goes(maybe).
20210202_144058.jpg
 

BERT

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Let me know if you got the picture please.the narrative from the start is as follows. On her maiden run there was scraping( chain/ inner) and oil drips. Both issues got worse after 20 or 30 miles so I shut her down. After loads of research(this forum and good books and the time for both) I decided to tackle these issues myself. After all, the best way to get to know a machine is to take it apart and try to figure it out, right? So the oil is leaking from the sump a bit, and while looking under her noticed 2 crankcase bosses on both sides are splayed away. I will try a weld repair on them on by someone who knows what they are doing. The scraping issue I think is caused by a few factors. On dismantling,the front vernier was way too loose(0.050"). Also the gearbox spacer was on the wrong side of the gearbox inside the cradle. I am also thinking that the combination of loose Iso's, wrong spacer location may have contributed to the crankcase damage. Anyways, this is keeping me busy and am enjoying the time with her, and I'll say it again, this forum is the best tool available.
 

grandpaul

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Somebody sure monkeyed with that bike!

You need to examine the frame and transmission cradle for proper (relative) alignment, since the case bosses are damaged, the transmission spacer was mis-installed and the isolastics were loose. There are enough forces at play to have slightly twisted some mounting points.
 

BERT

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Yes I will have a really good look at the frame as it's easier to eyeball with the power unit out. I used 1/2" drill rod through both the front iso mount, the rear iso mount and through the hole through the headstock(with a few wraps of duct tape for fit). The bars look parallel and the distance between centers is close to the frame dimensions in the shop manual. The headstock looks square to me. The rear iso rubbers were slightly crushed on one side and they look to me like they are fairly new, I wonder if that top spacer being on the wrong side deformed them. I should have taken a reference picture to show the axis of the pressure before I knocked it out of the tube. Hindsight is 20/20. Thanks for your input guys.
 

Craig

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Good for you taking a chance on an old bike , I’ve had a ‘72 for a long time , once everything put back in order they make a great Sunday rider .... enjoy the ride !
And Welcome
 

BERT

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Heeding to good advice(thanks grandpaul) I spent the last few days pondering the factors and examining the frame alignment with what I have on hand. Assuming (maybe not a good thing) the centerline of headsteady mount, the front iso mount, and the rear iso mount( cradle) is on the same plane as the centerline of the frame I jigged up datum points along these centers with threaded rods and flange nuts to clamp plumb lines to eyeball with. With the frame plumb through the headstock hole and a plumb line in front of the worktable for reference, I believe along this " z" axis everything is within a 1/16". The bottom tubes are not parallel (flat) . Along the "y" axis the d/s is level. The t/s tube is high about 0.050" at the rear before the 6" radius. Along the "x" axis at the front by the crosser the frame is level from d/s to t/a. At the rear the t/a is 0.050" higher than the d/s. From first observance when dismantling the rear iso, the rubbers on the t/s were crushed about that 0.050", I only wished I would have paid attention to the deformation axis. Now looking at some witness marks on the swing arm spindle from the cradle and swing arm and it needing a light drifting to remove, I am led to believe the t/s rear iso mount is needing to be lowered a bit. I wonder if the gearbox spacer being on the wrong side of the gearbox and the loose front iso mounts could have tweaked the frame and damaged the case bosses? Or vise versa? I don't know. I also discovered these kinks under nylon zip ties. Would this have been a sidecar mount point maybe? They look like some kind of clamping set up.
20210205_153106.jpg
20210205_152422.jpg
20210205_152924.jpg
 

BERT

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That is a good read. I had no idea how fussy these machines can be to set up decently. The article all makes sense to me, thanks gortnipper for linking it.
 

Craig

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Laser levels can be had for not much $ at Canadian Tire $20 or so .... what I have used for getting things straight ....
 

BERT

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Laser levels can be had for not much $ at Canadian Tire $20 or so .... what I have used for getting things straight ....
I have a Mastercraft which I don't use much as the beam is about 0.100" wide. I have found a water level the easiest to use if you get the right one. Leevalley sold one that came with a pail so there wasn't the wait for the water to settle after moving the mobile end. Thanks for mentioning that though, I forgot I had it and have been using plumb lines instead. I have used a surveyor's transit in the past in the construction business. If I can't get this frame straight, I'll keep moving back from it until it is straight. You can see a long ways through these instruments.Haha.
 

gortnipper

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Laser levels can be had for not much $ at Canadian Tire $20 or so .... what I have used for getting things straight ....
Yes, line one up from above and behind running down the spine before mounting tires and Midgard and you can easily see if everything lines up.
 

BERT

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I have got the bike down to the bare frame to try and tweak it into closer alignment. This region is still " stay at home order" so it will have to wait. I have finished lapping the oil pump to tighten the pinion end float and am looking at perhaps installing oil seals on the spindle to help. Input on this would be appreciated. There is a fair amount of side play between the spindle shaft and pump body on the scavenge side end plate. I don't know how critical this is. On dismantling there was a small shoulder formed by the torque of the drive gear nut which made the spindle tight to remove and made the sideplay less noticeable. The idler spindle and main spindle have a loose sliding fit thru the main body. There was 3 pieces of Al squished between the big gears. I noticed something in there rotating the pump after removing it, and after discovering pieces of paper gasket in an oil hole behind the pump, thought it may have been more gasket. No such luck. A few cogs are slightly damaged but I removed any burrs and undulations and will remesh the same gears on reassembly. I am glad Sir Isaac Norton used good Brit steel. That pump probably would have popped open with the stuff they make nowadays. It would be nice to find a seal modification I could have done at a machine shop.
When I dropped the front forks, I discovered tapered rollers installed on this 72. The bottom yoke had the "ANG" designation. On the top yoke spindle and the bottom yoke "266" is hand engraved. I don't know what it means, perhaps a logged fitting. I'm thinking it is definitely not the stock components and am now wondering if this bike has been crashed and fudged up, as the frame is slightly out of alignment. The steering assembly all made sense, with a spacer tube to preload the tapered bearings and a tab washer under the locknut. I wonder why the shop manual strictly states not to use "ANG" steering components on the 72.
The crankshaft had scratching on the t/s conrod journal which polished out easily. The shells on this side were worn to the copper. Both sides will be replaced. There was maybe a tablespoon of sludge inside the crank. Supposedly this crankshaft was dynamically balanced. How can I tell by looking at it and would removing this sludge affect the balancing? There is no indication the crank was dismantled before it was balanced.
The swingarm bushings were seized to the spindle(grease) which was pivoting on the engine cradle which is wore slightly. Oversize spindle will be installed.
Well folks, that's quite an earful to report and my finger is cramping up. More to add when I get to more part inspection. I hope everyone is keeping healthy and I'll say it again, this forum has been the best tool in the box and I really appreciate everyone who has listened and helped me along with this project. Thanks again. Dave.
 

L.A.B.

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There is a fair amount of side play between the spindle shaft and pump body on the scavenge side end plate. I don't know how critical this is.

Did you lap both sides (feed and scavenge) of the pump?


When I dropped the front forks, I discovered tapered rollers installed on this 72. The bottom yoke had the "ANG" designation. On the top yoke spindle and the bottom yoke "266" is hand engraved. I don't know what it means, perhaps a logged fitting. I'm thinking it is definitely not the stock components and am now wondering if this bike has been crashed and fudged up, as the frame is slightly out of alignment. The steering assembly all made sense, with a spacer tube to preload the tapered bearings and a tab washer under the locknut. I wonder why the shop manual strictly states not to use "ANG" steering components on the 72.

Apparently, 'ANG' yokes can be used with a 750 frame but they should be a pair of ANGs due to the difference in offset.

Non-ANG yokes hold the forks parallel to the steering axis.

ANG yokes, however, have an unequal offset between upper and lower, so the forks are not parallel to the steering axis (example, below).
SDC12930_(1)-001.jpg
 

BERT

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Did you lap both sides (feed and scavenge) of the pump?




Apparently, 'ANG' yokes can be used with a 750 frame but they should be a pair of ANGs due to the difference in offset.

Non-ANG yokes hold the forks parallel to the steering axis.

ANG yokes, however, have an unequal offset between upper and lower, so the forks are not parallel to the steering axis (example, below).
SDC12930_(1)-001.jpg
Thank you L.A.B.,
Yes, I lapped both sides. The spindle now has negligible end play if any.It was done to the shop manual procedure. The "side play" I previously mentioned I am unsure of is the diameter clearance between the spindle and end plate bore.
The yoke difference was well explained, I understand the difference. Thanks for that.
Best regards, Dave.
 
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