Knocking / rattling inside primary drive case + backfire

M-Hawk said:
I'm not bothered that it's actually a mk1 , and I'm only slightly miffed that it's not the smooth running bike that was described in the ad. There's absolutely no point looking to the private seller for a refund or anything of the sort.
Click to expand...

There's not all that much difference between the Mk1 and Mk2 except for the more desirable RH10 cylinder head of the Mk2/2A.
The Mk2A had the black plastic airbox with the battery repositioned across the frame to make space, black cap silencers (usually having been replaced with peashooters).
Also, there is little difference in value (Mk2/2A owners would probably disagree ;)) in my opinion.

Any update on the cause of the primary noise yet?
 
M-Hawk said:
Wow, what an amazing response. So much useful information. Thank you.

I have found and ordered both the Norton and Clymer manuals. I already have the Haynes and found it lacking detail.

I’ll work on removing the oil feed valve, makes sense.

I’ll keep this thread updated as I go. Should get time to do some bits this weekend.

Thanks again all.
Click to expand...
I would add the The Norton Commando Restoration manual from Norman White to your Christmas list, invaluable information from the man who knows.
 
Yes I would be interested in knowing what the noise/rattle in the primary was as well, think that be the first thing to be looking at before anything else.
 
The NOC's Commando service notes are worth a read, although the booklet is now as old as the bikes themselves and Norton knowledge has moved on a bit.

 
Story time!

A few years ago a 40 something that thought it would be cool to ride an old British bike, bought his first bike ever, an absolutely stock BSA B25. He was having trouble starting it and brought it to me for help. It started very easily for me, but the noise coming from the primary was unbelievable. I shut it off right away and assured him that the engine was about to go so he asked me to fix it. Long story short, when I took the primary cover off I could see that the rotor and stator were working as the drive-side main bearing. Once I dug deeper I could see that the drive side ball bearings were in the bottom of the crankcase.

The truly amazing part is that a new main bearing and a used stator and rotor was all it took for it to live again!
 
daveforty said:
The NOC's Commando service notes are worth a read, although the booklet is now as old as the bikes themselves and Norton knowledge has moved on a bit.

Click to expand...

When I read all those notes I got so overwhelmed I had to go lie down.

I'd just say to the OP that your photos look like you have a good bike with a couple of bugs to iron out.

The lists that I and others made would take the bike to pretty much perfect. If you like the bike then work on it over the years as time, money and knowledge evolves. It honestly took me over 40 years to get my Mk11 to pretty much how I want it - in my eyes.

Through those 40 years it only once failed to get me home. A broken wire down in the ignition trigger unit.
 
Another thing to check while you are inside the primary case is the alternator rotor. The outer part of the rotor with magnets can come loose from the cast-in steel sleeve in the centre that goes on the mainshaft. This lets the outer part rattle around and make noise.
 
I found a H2 forum, started asking for a source of CAST pistons.... when a genius began telling me to fit new pistons at .001" clearance.
I spend little time there.

(NOT saying that's the case here)


We are lucky to have a great source of information here at this site.
 
Hi all

Very sorry for the lack of updates. I've had a bunch of stuff to deal with that meant I haven't had the chance to touch the Norton, until today.

I finally took the primary chain case cover off. Here's a video:



I've never seen inside any chaincase let alone a Commando one, but the things that stand out to me are:

1) The clutch nut is only finger tight (although the clutch does seem to work, as demonstrated near the end of the video).
2) The primary chain looks like it's in good condition.
3) I didn't find any metal bits or debris in the drained oil or casing.
4) The chain tension seems ok?
5) The copper around the electrical connection to the rotor seems to be pretty close to the chain, although there are no signs that I can see of contact.
6) There's a small notch out of the rotor casing (the green bit) that doesn't look like it should be there. You can see this in the first few seconds of the video.

For reference, the video of the engine running with the rattling/knocking from the primary case is on post 1 of this thread.

What do you think? Is it simply a case of a loose clutch nut?
 
That nut should not be loose but is unlikely to be your noise. Loosen the clutch cable adjuster a the clutch lever, back that nut off and then turn the screw in the nut in until you feel it touch something. Back the screw off 1 turn and use the nut to lock the screw in place. Then readjust the cable at the handle bar.

You can run the bike with the cover off to see if it's easier to hear where the noise is coming from. Just be sure all oil is gone so you don't make a mess.

Also, the wire from the stator should be coming out of the other side, but that's probably no the problem either.
 
M-Hawk said:
5) The copper around the electrical connection to the rotor seems to be pretty close to the chain, although there are no signs that I can see of contact.
Click to expand...

Certainly, remove the stator, flip it over so the wire is correctly positioned on the outside and remove that copper wire. Maybe it was catching on the engine sprocket teeth, not the chain.


The clutch pushrod adjuster nut shouldn't be loose.
 
Last edited:
Thanks for the quick replies. I'll flip the stator, tighten & adjust the clutch cable and will then run the bike - as soon as I resolve an electrical issue that seems to have developed! Switching the ignition on blows the main fuse running from the battery. I'm guessing I must have a live to ground issue somewhere but there's nothing obvious. I did have the handlebar controls off to change the handlebar so maybe I've caused a short there somewhere.
 
At least you weren’t frightened away!

Welcome back.

How about a video of it running BEFORE you up that cover back on?

Also, check the rotor nut for torque, and the rotor gap with a feeler gauge.
 
There look to be no tab washers on the 3 inner primary chaincase retaining bolts, ordinary washers look to have been used, leaving the bolts free to come loose unless they have been locitied. Video is not clear enough so you best take some pics to confirm. You also haven't pulled and pushed on the main clutch body as its retaining nut could be loose, also pull and push on the alternator rotor.

Tab washer

andover-norton.co.uk

Andover Norton - LOCKING PLATE - 06.0395

LOCKING PLATE
andover-norton.co.uk
 
Last edited:
Re: electrical issue ....
1) Always go back to the last thing you changed

2) divide and conquer. Divide the electrical system into segments. Then test with one segment electrically isolated from the remaining system. Specifically, in your case, remove the feed to the
handle bar accessories, then test. Those more familiar with Commandos can tell you the wire code and color that would be.

Slick
 

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