Knocking / rattling inside primary drive case + backfire

Ok, so here's the update we've all been waiting for:

The good news
- The crank has no play in it at all, so I guess that means the main bearing is OK.
- The clutch spline is in good condition, and the clutch plates look OK too.

The bad news
- The clutch push rod is slightly bent (probably not a big deal as it seems to still fit and work OK). I'll order a new one in any case. Cheap enough.
- The sprocket was indeed loose on the taper, and I was able to remove it easily by hand. I've recorded a video inspection of the key and taper and also attached some photos of the sprocket. It's hard to get good light in there for pictures but hopefully these are detailed enough. If more pictures/video are required please let me know.
- Unsurprisingly, the sprocket woodruff key is a loose fit, and has visible signs of wear (see video).
- Consequently, there seems to be some (light?) scoring on the taper (visible as a slightly dark line, but I can't feel any score), and no corresponding marks on the sprocket that I can see or feel.

So, what do we think? All opinions welcome, thank you!



IMG_7160.jpeg

IMG_7161.jpeg

IMG_7162.jpeg
 
Last edited:
Try pushing the sprocket on while turning. It should lockup so you can't turn it. If not, get rid of any burrs and try again - 400-grit paper. If still no good, get some fine valve lapping compound and hand lap it - clean - try again. The key is not overly important - the taper is VERY important. If you can get the tapers to work and the crank is not sticking out of the sprocket and the sprocket is not touching the inner chaincase, you may be OK. Otherwise, you neeed a new sprocket and/or crankshaft or a very skilled machinist.
 
Thanks Greg.

Sprocket pushed on by hand, turns for a 1/8 turn and then sticks. I've tried to get photos of the gap at the back, and the front. Looks like I have enough clearance to play with?:

Knocking / rattling inside primary drive case + backfire


Knocking / rattling inside primary drive case + backfire
 
M-Hawk said:
Thanks Greg.

Sprocket pushed on by hand, turns for a 1/8 turn and then sticks. I've tried to get photos of the gap at the back, and the front. Looks like I have enough clearance to play with?:

View attachment 103580

View attachment 103581
Click to expand...

Ok, so the mystery appears to be what it was that prevented the engine sprocket from engaging (and so locking) onto the crank taper because tightening the rotor nut should press the engine sprocket tightly onto the crank taper.

Check the height of the woodruff key doesn't prevent the engine sprocket from fully engaging with the crank taper.
 
All looks good to me. It may have been those extra things they had on it. I would polish the taper and inside of the sprocket with some 400-grit (320 to 600) paper and do one more experiment. With everything very clean, put the sprocket, spacer, and rotor on and tighten to around 10 ft lp. Then take the rotor and spacer off and see if you can get the sprocket off by hand only. If not, pull it and then reassemble the primary without the stator. Start it and see if the noise is gone. If so, get back on the stator clearance.

Edit: By polish I mean only be sure any burrs are gone - you don't want to remove metal. Also, L.A.B.'s comment about the key is important. They aren't usually very tight but do need to fit down into the crank well and not bind the sprocket.
 
Last edited:
Ok, thanks both.

I have just polished the taper and inside of sprocket, very lightly with 400 and then 1200 grit. I put the sprocket on, then the recessed spacer (recess outwards), then the rotor. Tightening to 10 ft lb doesn't even get the nut close to the rotor. This video shows how much play I've got:



Is this because the sprocket goes too deep on the taper?

I guess this is the problem that the previous owner tried to fix using the 6mm collar.

EDIT: The above was with no woodruff keys in place.
 
M-Hawk said:
Ok, thanks both.

I have just polished the taper and inside of sprocket, very lightly with 400 and then 1200 grit. I put the sprocket on, then the recessed spacer (recess outwards), then the rotor. Tightening to 10 ft lb doesn't even get the nut close to the rotor. This video shows how much play I've got:



Is this because the sprocket goes too deep on the taper?

I guess this is the problem that the previous owner tried to fix using the 6mm collar.

EDIT: The above was with no woodruff keys in place.
Click to expand...

Looks like you have the wrong spacer in there
Order a new one from AN
But in the meantime find some washers or something to take up the space
And try the test again
 
marinatlas said:
www.rgmnorton.co.uk

ROTOR SPACER

060402 RGM NORTON
www.rgmnorton.co.uk

according to RGM the spacer width is 9/16 (14.3mm) check with yours
Click to expand...
Thanks, interesting. My spacer is 14mm ish, so seems correct:

Knocking / rattling inside primary drive case + backfire


Perhaps my rotor is non-standard, and narrower, due to the stator being the high output 3-phase type?

I used our old friend the 6mm collar to perform the test (see here in-situ behind the rotor nut), and was able to tighten the stack to 10 ft lb.

Knocking / rattling inside primary drive case + backfire


I then removed the rotor and spacer and am happy to report that the sprocket is not wobbling and I can't get it off by hand. This is it's seating position:

Knocking / rattling inside primary drive case + backfire


I'm going to find the standard rotor dimensions and check against mine next...
 
Take the rotor off and screw the nut on to see how far it goes on. There should be no need for anything else unless something you have has been modified. Give us a picture of the nut on without the rotor.
 
Ok, here's a picture of the nut in as far as it goes before the engine starts turning.

Clearly not far enough. Looks like the nut has a load of gunk in it, blocking the thread.

I assume it's supposed to be able to butt right up to the shaft?

I'll clean the nut out and try again.

IMG_7172.jpeg
 

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  • Knocking / rattling inside primary drive case + backfire
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M-Hawk said:
Perhaps my rotor is non-standard, and narrower, due to the stator being the high output 3-phase type?
Click to expand...

"54212006" is the standard rotor. The fact that the (Wassell) stator is 3-phase shouldn't make any difference.
M-Hawk said:
Clearly not far enough. Looks like the nut has a load of gunk in it, blocking the thread.
Click to expand...

Yes, or it's not the correct thread.
 
Run a tap thru the nut.
All: What is the thread size and pitch?

Slick

EDIT ...... if any doubts, get a new nut!
 
I've managed to sort the nut enough to get the rotor tight on, without the use of the 6mm collar. I'll order a new nut though.

I've tried to measure the gap between sprocket and casing:

IMG_7173.jpeg


Also, checking alignment of sprocket with clutch drum it looks like the sprocket needs to go in by about 4 or 5mm more. Then, it's only on 'test' at the moment at 10 ft lb. Could I expect that 4mm or so to be taken up with a full torque of 70 ft lb?

IMG_7175.jpeg
 
M-Hawk said:
I've tried to measure the gap between sprocket and casing:
Click to expand...

As long as the nose of the crank taper doesn't protrude from the sprocket there shouldn't be a problem.

Under normal circumstances, the shims as mentioned earlier would also space the rotor out a little.
M-Hawk said:
Also, checking alignment of sprocket with clutch drum it looks like the sprocket needs to go in by about 4 or 5mm more. Then, it's only on 'test' at the moment at 10 ft lb. Could I expect that 4mm or so to be taken up with a full torque?
Click to expand...

Probably not that much, there would typically be alignment shims between the clutch spacer (the recessed side does go inwards on this spacer) and the clutch drum sprocket. Assuming these shims were not missing?

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
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
 

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