Knocking / rattling inside primary drive case + backfire

M-Hawk said:
Option 3 has become mandatory :(
Click to expand...
Yep. If you find a used one, you know how to fit it. If you buy a new one, be careful that is fits to the engine completely. The hole in the inner cover should be a snug fit on the engine case and new ones are often a little too snug allowing room for light dressing to get them on right.

I put the studs in with fingers using blue locktite until the last quarter turn and then snug them. The point being that you don't want them to unscrew when removing the nuts to remove the stator.
 
Last edited:
M-Hawk said:
Ah, I'm an idiot.
Click to expand...
Live and learn. The good news is that you can see the crap threads in the picture, so it was someone before you that started this issue as well.

My rule of thumb is that when screwing into aluminum, if it won't go with fingers then you need to clear out the hole and maybe chase the threads. The same is actually true of steel and cast iron, but things don't go sideways as fast when in steel or case iron.
 
M-Hawk said:
Yeah, at least I know how to take it apart and put it back together again.
Click to expand...
If you can find a good used one you may save one headache. IMHO, the hardest job on a Norton is installing the felt washer that "seals" the gearbox main shaft (in the sliding plates behind the clutch). Hopefully, someone here installed the cNw e-start and has a good inner primary left over.
 
That's a bummer, but I reckon you could get that welded. In fact if you do you can get it filled and then put the stud back in the correct position. But as Greg mentioned above, there should be a few covers around though after CNW or Alton starter conversions. Why don't you put a wanted ad here..

Classifieds

www.accessnorton.com www.accessnorton.com
 
texasSlick said:
Is there an option to weld the post, then drill and heicoil the hole?

Sigh! ...... if it isn't one thing, it's another one on the way.

Slick
Click to expand...
Certainly could be done if properly equipped, but the time and materials required cost way more than a used replacement and maybe more than a new one.
 
Norman White in his Restoration book page 112 states his method for dealing with stator alignment issues:
Knocking / rattling inside primary drive case + backfire
 
Tornado said:
Norman White in his Restoration book page 112 states his method for dealing with stator alignment issues:
View attachment 103938
Click to expand...
I have done allsorts of things to get a good air gap clearance
If you drill the stator you need to radius the cutting edge of the drill bit
The same as you would to drill a dead size hole
Also you can waist two of the alternator studs
Or the overall diameter of the rotor
I believe fast Eddie does this as a matter of course
With no ill effects
 
Thanks. Already put a wanted ad up. Nothing yet but early days. Ironically I had just figured out that this was the only stud in the correct position.
 
baz said:
I have done allsorts of things to get a good air gap clearance
If you drill the stator you need to radius the cutting edge of the drill bit
The same as you would to drill a dead size hole
Also you can waist two of the alternator studs
Or the overall diameter of the rotor
I believe fast Eddie does this as a matter of course
With no ill effects
Click to expand...
Yes I get the rotor turned down to a .020” gap, ie .040” under size. I read this years ago in Stan Shenton’s Triumph Tuning book. I get both the rotor and stator measured and then remove what’s required for 0.040” undersize.

My Commando had definite signs of rubbing at .010”. I’ve not had issues at .020” gap.

I do this a ‘standard’ on all my old Brits now.

I got the bits on the Commando measured carefully after it rubbed to try and see if there was another root cause. The rotor for roundness and concentricity to the bore, the stator for roundness of the ID and concentricity to the mounting studs, and maybe some other stuff I’ve forgotten. Basically, it was all good. So it was going oversize with the gap that made the difference.

My thinking is that these old things flex more than we might realise, something that’s probably exponentially affected by rpm, so someone who seldom sees 5k rpm will be much less affected than someone who sees 6k+ frequently.

As an aside, I believe that modern pattern parts cannot be trusted to even give a .010” gap, I’ve seen them tighter than that, as have others. My hypothesis is that the manufactures think ‘tighter is better’ as they would on a modern machine, and perhaps don’t really understand the nature of old Brit bikes.

As to whether any electrickery is lost by having a bigger air gap, I don’t know. It would require someone cleverer than me to ascertain that. I‘ve never measured it and never noticed any ill effect.

I’ve also drilled out the stator mounting holes on a couple of occasions and don’t quite understand why I didn’t have any problems doing so, maybe my drill bits are nicely radiused (ie blunt) !?
 
Last edited:
I believe the only reason you would require more than 10 thou is if your rotor, when mounted, is out of round.
A dial indicator will tell you this and where material, if any, has to be removed.
Increasing the gap will have a detrimental effect on the capacity of the alternator.
 
robs ss said:
I believe the only reason you would require more than 10 thou is if your rotor, when mounted, is out of round.
A dial indicator will tell you this and where material, if any, has to be removed.
Increasing the gap will have a detrimental effect on the capacity of the alternator.
Click to expand...
I disagree. I measured everything I could and could see no run out. I therefore think it’s flex. Even if there was run out, if there was clearance it should not touch, unless that clearance changes when running.

It would be great if someone could measure that detrimental effect on charging. I’m not saying there is no measurable loss, but I can say there is no practical detectable loss ie zero evidence of any loss in actual use.

Back to the gap and flex, if we think about it this way: if the gap (whatever the size) was not changed by either heat or rpm, then the gap we measured when cold would stay the same when hot and spinning. So even if we only had a 0.001” gap, it would never touch.

Therefore, something to do with heat and rpm reduces the gap on a running engine.

Therefore, it’s reasonable to assume that those factors are relative, ie the higher the rpm, the greater the effect.

The only things that I can think of that change with heat and rpm are expansion (heat) and flex (rotational forces).

So, maybe the gap reduces due to expansion, ie maybe the rotor expands more than the stator (highly likely IMHO) and maybe there is flex (a definite factor IMHO). This could be flex anywhere in the system, ie the rotor may distort, the cases, and the crank nose (that crank nose is long, relatively small diameter, and has a hulking great weight on the end of it). I would also suggest that crank flex inside the cases (which we know happens) is also going to transmit to the crank nose as that flex acts on the main bearing as a fulcrum.

Flex is a funny thing. I was once in the test lab at Mercedes when they had an AMG 6.2 litre V8 on the bed that they were videoing for flex. The slow motion video was AMAZING. These V8 blocks are huge, and heavy, and seemingly solid. But in that video they looked like jelly on a plate ! Which was a good thing apparently, as one guy said to me “if zer ist no flex… zen it vill break” …
 
Last edited:
Fast Eddie said:
Yes I get the rotor turned down to a .020” gap, ie .040” under size. I read this years ago in Stan Shenton’s Triumph Tuning book. I get both the rotor and stator measured and then remove what’s required for 0.040” undersize.

My Commando had definite signs of rubbing at .010”. I’ve not had issues at .020” gap.

I do this a ‘standard’ on all my old Brits now.

I got the bits on the Commando measured carefully after it rubbed to try and see if there was another root cause. The rotor for roundness and concentricity to the bore, the stator for roundness of the ID and concentricity to the mounting studs, and maybe some other stuff I’ve forgotten. Basically, it was all good. So it was going oversize with the gap that made the difference.

My thinking is that these old things flex more than we might realise, something that’s probably exponentially affected by rpm, so someone who seldom sees 5k rpm will be much less affected than someone who sees 6k+ frequently.

As an aside, I believe that modern pattern parts cannot be trusted to even give a .010” gap, I’ve seen them tighter than that, as have others. My hypothesis is that the manufactures think ‘tighter is better’ as they would on a modern machine, and perhaps don’t really understand the nature of old Brit bikes.

As to whether any electrickery is lost by having a bigger air gap, I don’t know. It would require someone cleverer than me to ascertain that. I‘ve never measured it and never noticed any ill effect.

I’ve also drilled out the stator mounting holes on a couple of occasions and don’t quite understand why I didn’t have any problems doing so, maybe my drill bits are nicely radiused (ie blunt) !?
Click to expand...
To be clear it's not to blunt (radius) the cutting edge of the drill bit
It's to radius it along the cutting edge not across
It's a trick to drilling a perfect size hole without reaming
It helps stop the outside edge of the drill from digging in
Taught to me by an old toolmaker
 
Last edited:
Fast Eddie said:
I disagree. I measured everything I could and could see no run out. I therefore think it’s flex. Even if there was flex, if there was clearance it should not touch, unless that clearance changes when running.

It would be great if someone could measure that detrimental effect on charging. I’m not saying there is no measurable loss, but I can say there is no practical detectable loss ie zero evidence of any loss in actual use.

Back to the gap and flex, if we think about it this way: if the gap (whatever the size) was not changed by either heat or rpm, then the gap we measured when cold would stay the same when hot and spinning. So even if we only had a 0.001” gap, it would never touch.

Therefore, something to do with heat and rpm reduces the gap on a running engine.

Therefore, it’s reasonable to assume that those factors are relative, ie the higher the rpm, the greater the effect.

The only things that I can think of that change with heat and rpm are expansion (heat) and flex (rotational forces).

So, maybe the gap reduces due to expansion, ie maybe the rotor expands more than the stator (highly likely IMHO) and maybe there is flex (a definite factor IMHO). This could be flex anywhere in the system, ie the rotor may distort, the cases, and the crank nose (that crank nose is long, relatively small diameter, and has a hulking great weight on the end of it). I would also suggest that crank flex inside the cases (which we know happens) is also going to transmit to the crank nose as that flex acts on the main bearing as a fulcrum.

Flex is a funny thing. I was once in the test lab at Mercedes when they had an AMG 6.2 litre V8 on the bed that they were videoing for flex. The slow motion video was AMAZING. These V8 blocks are huge, and heavy, and seemingly solid. But in that video they looked like jelly on a plate ! Which was a good thing apparently, as one guy said to me “if zer ist no flex… zen it vill break” …
Click to expand...
If it is taken that the rotor in inherently balanced then there is no flex inducement from that, the only other source of flex would be the crankshaft (whipping due to the engine running). I would be very surprised if there was more than 10 thou at the alternator rotor from that.
Are you sure your rotor was "dialled" for run-out?
I have 3 Nortons running with 10 thou clearance without any indication of rubbing. (one is a single)
 
robs ss said:
If it is taken that the rotor in inherently balanced then there is no flex inducement from that, the only other source of flex would be the crankshaft (whipping due to the engine running). I would be very surprised if there was more than 10 thou at the alternator rotor from that.
Are you sure your rotor was "dialled" for run-out?
I have 3 Nortons running with 10 thou clearance without any indication of rubbing. (one is a single)
Click to expand...
I even had the rotor dynamically balanced! It was not actually inherently balanced, it did need some (admittedly very small) drillings.
 
Last edited:
Fast Eddie said:
I even had the rotor dynamically balanced! It was not actually inherently balanced, it did need some small drillings.
Click to expand...
Just checked the rotor clearance on my Matt's build #134 - no discussion between us on this issue and I have never checked/adjusted this.
Checked the rotor clearance, starting at 20 thou - no way this will fit in. Continued to reduce feeler gauge size.
At 14 thou I could get it in and around about 2/3rds of the way around.
At 10 thou it will go all the way around with one spot being a bit "tight" - so say 9 thou there.
Supports my long held belief that 10 thou is adequate, but, to each their own 👍

I, unlike some, stay within the recommended redline. You Nigel?
I have pushed it to 7500 in top a few times though - shhhh!! (no tracks within 500km)
 
Last edited:
robs ss said:
Just checked the rotor clearance on my Matt's build #134 - no discussion between us on this issue and I have never checked/adjusted this.
Checked the rotor clearance, starting at 20 thou - no way this will fit in. Continued to reduce feeler gauge size.
At 14 thou I could get it in and around about 2/3rds of the way around.
At 10 thou it will go all the way around with one spot being a bit "tight" - so say 9 thou there.
Supports my long held belief that 10 thou is adequate, but, to each their own 👍

I, unlike some, stay within the recommended redline. You Nigel?
Click to expand...
Thats only half of the test Rob… Now you just have to dismantle it to see if it has rubbed !

Redline is at 7,000. I stick to that ‘most’ of the time…
 
robs ss said:
Just checked the rotor clearance on my Matt's build #134 - no discussion between us on this issue and I have never checked/adjusted this.
Checked the rotor clearance, starting at 20 thou - no way this will fit in. Continued to reduce feeler gauge size.
At 14 thou I could get it in and around about 2/3rds of the way around.
At 10 thou it will go all the way around with one spot being a bit "tight" - so say 9 thou there.
Supports my long held belief that 10 thou is adequate, but, to each their own 👍

I, unlike some, stay within the recommended redline. You Nigel?
Click to expand...
Interesting - you're describing pretty much where I started at.
 
You must log in or register to reply here.
Back
Top