Crank movement

baz said:
My mk2a had 24 thou end float from the factory with no issues
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A mate of mine that builds jet sprint V8 motors for people from all over the place that basically scream recommended i should shim othe crank and the rocker shafts while I was in there...he's super fussy
The rocker arm work seems far more beneficial
 
baz said:
I agree with you Ash about the motor
But I'd have to pull the gearbox to check if the Portuguese layshaft bearing had been banished
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Well not knowing if that Portuguese LS bearing has been replace, but 47 years and it hasn't blown yet, mine was only 3 years old when it blew, still I wouldn't rip a GB apart if it's working good, mine blew outside my house when I put it in gear, but if you worry about things all the time that might never happen, fix things when need too but no need to fix things if all is going good, I just never think about it and enjoy the ride, we all have our own opinions with doing things but I trust my Norton after 46 years ownership if I worried about things breaking I never ride it very far.
 
ashman said:
Well not knowing if that Portuguese LS bearing has been replace, but 47 years and it hasn't blown yet, mine was only 3 years old when it blew, still I wouldn't rip a GB apart if it's working good, mine blew outside my house when I put it in gear, but if you worry about things all the time that might never happen, fix things when need too but no need to fix things if all is going good, I just never think about it and enjoy the ride, we all have our own opinions with doing things but I trust my Norton after 46 years ownership if I worried about things breaking I never ride it very far.
Click to expand...
With the Portuguese bearing it's not if it's when
It's a bit different to other issues with our beloved bikes as it can sit you on your arse
I don't worry about anything in my my bike either
I just disagree with you over that bearing đź‘Ť
 
A 50 year old machine has a good chance of having had substandard work done to it. Every owner has their unique situation. Some(as I) have a short riding season who would rather ride than repair. Others have a lengthy riding season who don't mind a repair in between. I had the time, skill, tools, a comfortable place to work, and the support( manuals and this Forum) to totally dismantle, inspect, and reassemble this 72 to make it a trustworthy(so far) machine. It was done in 1 winter and gave me the confidence to tackle any task on it in the future. It is a great way to learn the machine inside and out. It depends on what type of person one is I suppose.
 
Thanks for all the responses! I did see the allowable tolerances in the Mk3 workshop manual and read the other threads on the topic. I'm trying not to over think this but I'm still not clear as to why there would be no measurable movement at all unless it's not apparent with the timing chest assembled.

Not to obscure my question, but there is one strange noise I encountered when I run the bike. At an idle in neutral there was an occasional knock, more like a crack similar to a carb backfire coming from what I believe to be the primary case. I attributed to the automatic primary chain adjustment not being primed, and once I primed the adjuster, the noise at idle was resolved except I could still hear it briefly under hard throttle just off the idle. Still thinking it's the primary chain adjuster but now that I have it disassembled, I don't see any witness marks of the chain hitting the cover. Wondering if the chain adjuster pistons are capable of making a slapping noise if they are not primed correctly. I have a video of it, perhaps I'll post it in another thread.
 
2WheelsUp said:
Thanks for all the responses! I did see the allowable tolerances in the Mk3 workshop manual and read the other threads on the topic. I'm trying not to over think this but I'm still not clear as to why there would be no measurable movement at all unless it's not apparent with the timing chest assembled.
Click to expand...
You have a running engine - if your crank turns freely, quit thinking about it! The cases grow when they warm up. IMHO 0.000"-0.024" is fine (as long as the crank turns freely).

If you really want to know:
1) Disassemble the timing chest and recheck, If still no play:
2) Split the cases and:
a) See if the bearings are properly seated
b) Remove the bearings to see if there are shims on the crank or in the cases
c) Check that the crank center bolts are not loose.

Still, as I said many posts ago, I don't shim Norton cranks.

I've only ever found one greater than 0.024" and there was evidence of machine work on the flywheel where the cheeks attach - no clue why so I didn't use it.

I found one with about -0.004" and that one had shims on both sides of the crank itself. It was a basket case and probably why it was sold rather than built.

I found one with the center bolts appeared tight, locktited, and peened, but the cheeks not flat on the flywheel - no end float and you could see the flywheel wobble as you turned it - imagine how quicky it would have destroyed itself if started - another basket case.
 
2WheelsUp said:
Still thinking it's the primary chain adjuster but now that I have it disassembled, I don't see any witness marks of the chain hitting the cover. Wondering if the chain adjuster pistons are capable of making a slapping noise if they are not primed correctly.
Click to expand...

Yes, they can until the system has primed. Which type of oil are you using in your Mk3's primary case because the often recommended ATF doesn't work well with the Mk3's automatic chain tensioner (too thin) and can result in the chain thrashing around?

Check the nylon plugs are fitted with the 'heads' against the springs or the plungers will be under-tensioned.
https://www.accessnorton.com/Norton...c-tensioner-assembly-doesnt-make-sense.27790/

Also that the gasket 27A is fitted between the plate 29 and tensioner body.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
 
Last edited:
L.A.B. said:
Yes, they can until the system has primed. Which type of oil are you using in your Mk3's primary case because the often recommended ATF doesn't work well with the Mk3's automatic chain tensioner (too thin) and can result in the chain thrashing around?

Check the nylon plugs are fitted with the 'heads' against the springs or the plungers will be under-tensioned.
https://www.accessnorton.com/Norton...c-tensioner-assembly-doesnt-make-sense.27790/

Also that the gasket 27A is fitted between the plate 29 and tensioner body.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
Click to expand...
Think I put engine oil into it 20/50 ... definitely not ATF fluid. I'll look at the nylon plugs as you suggested... actually saw that thread a while back when I first encountered the issue but didn't feel comfortable pulling it apart at the time. I attempted to prime it by pouring oil into the cavity until it was full but later read in the workshop manual the correct procedure requires you to squeeze the tensioner ends a few times to get the oil worked into the tensioner... I didn't do that. Like I mentioned, I did see improvements, just not completely resolved but I'm reasonably confident I'm on the right path. Next step is to remove engine/gearbox from the frame, posting a question about that shortly.
 
2WheelsUp said:
Think I put engine oil into it 20/50 ... definitely not ATF fluid.
Click to expand...

Ok, I use 20w/50.

2WheelsUp said:
I attempted to prime it by pouring oil into the cavity until it was full but later read in the workshop manual the correct procedure requires you to squeeze the tensioner ends a few times to get the oil worked into the tensioner... I didn't do that.
Click to expand...

Yes, the plungers need to operate to prime the tensioner although the tensioner should self-prime after the engine starts but it can take a minute or two because the oil drains from the tensioner after the engine has stopped so the odd clonk isn't something you need to be too concerned about as long as it stops a short time after the engine is restarted.
 
baz said:
With the Portuguese bearing it's not if it's when
It's a bit different to other issues with our beloved bikes as it can sit you on your arse
I don't worry about anything in my my bike either
I just disagree with you over that bearing đź‘Ť
Click to expand...
Knowing now what I experienced from that issue at speed... a must do job regardless
 
marshg246 said:
You have a running engine - if your crank turns freely, quit thinking about it! The cases grow when they warm up. IMHO 0.000"-0.024" is fine (as long as the crank turns freely).

If you really want to know:
1) Disassemble the timing chest and recheck, If still no play:
2) Split the cases and:
a) See if the bearings are properly seated
b) Remove the bearings to see if there are shims on the crank or in the cases
c) Check that the crank center bolts are not loose.

Still, as I said many posts ago, I don't shim Norton cranks.

I've only ever found one greater than 0.024" and there was evidence of machine work on the flywheel where the cheeks attach - no clue why so I didn't use it.

I found one with about -0.004" and that one had shims on both sides of the crank itself. It was a basket case and probably why it was sold rather than built.

I found one with the center bolts appeared tight, locktited, and peened, but the cheeks not flat on the flywheel - no end float and you could see the flywheel wobble as you turned it - imagine how quicky it would have destroyed itself if started - another basket case.
Click to expand...
Thanks!
 
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