Knocking / rattling inside primary drive case + backfire

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cliffa said:
I’m not sure if you checked it already, but as L.A.B. mentioned earlier, I would definitely check that when installed, the woodruff key is not taller than the keyway, as that would obviously stop the sprocket seating properly on the taper
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I’m a bit confused by this. I was reading up about how woodruff keys work, including https://www.huyett.com/blog/woodruff-keys

So isn’t the flat part of the key supposed to stick out of the keyway a little?

Sorry if I’m being dumb here 😁
 
A nonstock mod I would recommend since it is apart is, the small oring over the crank against the seal.
This helps seal the crankcase better.
Here's the write up, from Mr. Schmidt, Jseng1.
The only real (very rare) problem wet sumping can cause is blowing out the crank main seal. You can avoid that problem by installing a 1-1/8" ID 3/32 wall viton oring between the primary sprocket and the main seal. Its a #122 oring and you can get them for cheap at suppliers like Mcmaster Carr. Wet sumping also makes it a little harder to kick over the motor but its not much of a problem on kirk start 750s or 850 Mk3s with electric start.

Along with the o ring, I would replace the crank seal... Just because.... after the little sanding/polish recommended by Mr. Marsh.
 
MichaelB said:
A nonstock mod I would recommend since it is apart is, the small oring over the crank against the seal.
This helps seal the crankcase better.
Here's the write up, from Mr. Schmidt, Jseng1.
The only real (very rare) problem wet sumping can cause is blowing out the crank main seal. You can avoid that problem by installing a 1-1/8" ID 3/32 wall viton oring between the primary sprocket and the main seal. Its a #122 oring and you can get them for cheap at suppliers like Mcmaster Carr. Wet sumping also makes it a little harder to kick over the motor but its not much of a problem on kirk start 750s or 850 Mk3s with electric start.

Along with the o ring, I would replace the crank seal... Just because.... after the little sanding/polish recommended by Mr. Marsh.
Click to expand...
Thanks for this. I’ll try to find the correct o ring here in the UK.

Crank seal on order. I thought the same :)
 
M-Hawk said:
I’m a bit confused by this. I was reading up about how woodruff keys work, including https://www.huyett.com/blog/woodruff-keys

So isn’t the flat part of the key supposed to stick out of the keyway a little?

Sorry if I’m being dumb here 😁
Click to expand...
Yes, that’s correct, however if the incorrect key has been fitted and it protrudes too much from the shaft it will not allow the pulley to fully seat on the taper (which is imperative). It may be fine, but as you already have it apart it’s worth checking. You can probably just use a vernier to measure how far above the taper it protrudes when set parallel and then compare that to the depth of the groove in the sprocket. I hope that makes sense.

Edit: this may make it clearer.

Dimension C should not be greater than dimension E below..


Knocking / rattling inside primary drive case + backfire
 
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You have to assume all the woodruff keys on the primary side are botched, so buy all new keys from a Norton supplier and that should remove doubt. You are left with the key ways being the wrong size by previous use of loctite or burrs.
 
kommando said:
You have to assume all the woodruff keys on the primary side are botched, so buy all new keys from a Norton supplier and that should remove doubt. You are left with the key ways being the wrong size by previous use of loctite or burrs.
Click to expand...
New keys are on the order. Hopefully the keyways are OK.
 
MichaelB said:
A nonstock mod I would recommend since it is apart is, the small oring over the crank against the seal.
This helps seal the crankcase better.
Here's the write up, from Mr. Schmidt, Jseng1.
The only real (very rare) problem wet sumping can cause is blowing out the crank main seal. You can avoid that problem by installing a 1-1/8" ID 3/32 wall viton oring between the primary sprocket and the main seal. Its a #122 oring and you can get them for cheap at suppliers like Mcmaster Carr. Wet sumping also makes it a little harder to kick over the motor but its not much of a problem on kirk start 750s or 850 Mk3s with electric start.

Along with the o ring, I would replace the crank seal... Just because.... after the little sanding/polish recommended by Mr. Marsh.
Click to expand...
I think I've found a supplier for the mod o ring. Do you think the durometer rating matters? 70, 75 or 90 ShA are the options

Knocking / rattling inside primary drive case + backfire
 
It does look like what you have is all serviceable
Just pay particular attention to assembly
Especially the 3 chaincase retaining bolts
The clutch center nut
Alternator clearance
Whilst the alternator rotor is off give it a check in a vice by clamping the centre with a couple of washer's clamping the centre (metal part)
Then try turning the outer (aluminium part) backwards and forwards
There should be no movement
The chain alinement isn't absolutely critical it ain't a" space ship " as said above
But it should be shimmed as good as you can get it
 
M-Hawk said:
I think I've found a supplier for the mod o ring. Do you think the durometer rating matters? 70, 75 or 90 ShA are the options

View attachment 103618
Click to expand...
What Kommando said above. Oil and heat resistant.

On your AN order I would add the various crush washers for servicing, Various drain plugs and the double aluminums on the oil tank. Just to have them. If you haven't already filled it.
 
Tiny thing to watch. The front sprocket key is usually not tight in the slot of the crank or sprocket. When putting the sprocket on, the key can slip backwards and bind which is about the same thing as the key being too tall. You should be able to see it in the slot as you push the sprocket on.
 
I assume we are waiting on parts?.............. 🧐................ or the honey doo list has taken priority.
 
Mini update - before even loosening the inner primary case, I noticed that the centre stud isn’t centrally located around the case. This made me suspect a lack of shims on the centre stud.

Sure enough, after removing the inner case I found 1 x gasket, but no shims. I’m hopeful that correct shimming will straighten it up and resolve the stator alignment problem.

The inner case bolts only had blue thread lock on them by the way, and were not difficult to undo.

More updates in a bit..

F331558A-4D3D-44D2-91A8-5C8D7453BC4D.jpeg
 
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M-Hawk said:
Yep - parts have now arrived. I'll be making a start this afternoon.

I'm going to re-read the entire thread, make notes and take my time :)
Click to expand...
That's a really good idea. A properly set up primary allows for a sweeter Commando.
Starting with the gear box, observe the main shaft alignment parallel with the crank. There's movement there.
On to the inner cover, you'll find a little movement in the placement of the screws.
I try to align the cover to center on the mounting stud. Set shims or gaskets as necessary for flush fit.
So on and so on...

Edit..you must posted while I was typing. Yes, straighten that up and things get better.
 
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