Scrap primary inner case...

Bob Z. · Aug 28, 2014

Looking at this primary inner case, is it salvageable?
Maybe it just serves as an example of what happens when the primary drive side is not adjusted properly.

The crack at the front mount was most certainly caused by not having a proper spacer/washer behind the chaincase center stud. Checking the flatness of the gasket surface shows a high spot.

More interesting is the drive chain wear pattern and the swing arm end plate wear in the rear of the case.
The steel sliding felt seal disc is worn through in an area, and the heavy chain wear indicates that without proper center stud alignment, tightening the primary cover nut will bend the whole primary case towards the drive sprocket.

This would also affect the alternator rotor/stator clearance as the stator is fixed to the inner cover.

Hobot · Aug 28, 2014

JBWeld could save it. I'd fill small drill holes in the fracture with a strong magnet taped on other side to draw in deeply. Could JBW plaster over the chain score damage then smooth over before setting with it leveled to gravity and diddle felt plates back on with grease or dry graphite under. The inner cover has nothing to do with alternator/stator clearance but clutch basket can rub if case or clutch not shimmed spaced right. If used for dry belt just leave the tin can felt seal thing out.

john robert bould · Aug 28, 2014

Before repairing..what caused it will do its damage again...swing arm issues?

Hobot · Aug 28, 2014

The cover was put on w/o proper spacer behind center post so when outer cover nut tightened up it levered apart the front mount boss and angled rear end of case too far into chain path. For want of a nail in a horse shoe...

Bob Z. · Aug 28, 2014

The primary case is from a basket case bike that has sat for many years.

Speculation, long ago the bike may have come apart for the main bearing upgrade, and was not re-assembled well.
Does the stamped X on the timing side crankcase have any meaning?

Oh, Norton 142780, what happened to you, way back when?

Biscuit · Aug 28, 2014

JB Weld is a good product but it has it's limitations, not being in the least bit flexible being one of them. If after being repaired with the stuff the shimming is not dead nuts perfect I believe vibration will cause it to crack again. (vibration? what vibration?) I'd get it to a good welder and fix it properly....And another reason I like my MK3. :mrgreen:

Bob Z. · Aug 28, 2014

So how many have had the left footrest nut punch into the outer case?

Nater_Potater · Aug 28, 2014

Bob Z. said:
So how many have had the left footrest nut punch into the outer case?

That last image would point to the bike being dumped on its left side with the footpeg pushing the primary over, cracking the mounting flange, then wearing the chain grooves as the PO continued to ride it after "repairing" the hole under the footpeg. If that's truly the case, I would suspect the inner cover's center mounting hole to be pushed towards the inside of the primary case.
Before having the flange welded, it might behoove you to do a dye-check to the center hole.

Nathan

L.A.B. · Aug 28, 2014

Bob Z. said:
Does the stamped X on the timing side crankcase have any meaning?

It's just about the only factory code stamp that I think we do know the meaning of.
According to a Norton service release, the 'X' apparently signified that an engine had been fitted with modified piston 2nd rings in an attempt to reduce oil consumption.

Hobot · Aug 28, 2014

This is a rather low stress application for JBW and only inexperience with its capabilities would give anyone a second thought not to use it here if they cared about re-using the case. Ms Peel had 1' cover foot peg bolt/nut punched in from THE Gravel crashes and also prior punched out by a crank nut flung off, both fractured enough to leak but both permanent fixed about undetectable by hammering flush-ish, filing, sanding then JBW back sides to seal, same with Trixie's twice busted out crank cases by Norton rod failures ***after*** a piston and later a cap bolt let go. I never want to deal with hot welding distortion in cast Al cases again. Of course if ya let on using JBW instead of welding and blacksmithing metal working back to snuff - you'll forever be thought of as life time member of hobot's black sheep dating pub. Best respectable path is just buy another to support a vendor or clean up someones excess clutter then make a Norton clock out of the fractured one.

Biscuit · Aug 28, 2014

Sorry man, I have the greatest respect for JB glueing as much as the next Nortoneer but sometimes real metel is the bestes fix for real metal injuries. I believe a crack by it's very nature ain't done yet and asking epox to stop the madness not always the answer with oil impregnated damage Mr H.

ashman · Aug 28, 2014

I have just gone throught this after replacing my inner case, I didn't put enough spacer between the mounting bolt and my chain rubbed on the sliding seal, the noise wasn't heard from the chain rubbing and after a few months the chain joining link fowled up the sliding seal and lost the joining link that left me stranded on the side of the road (first time in 39 years).
But in you pics and the damage to the front of the case, the footpeg damage and worn mount hole I say that the bike has been down and it has hit pretty hard, with not enough spacers behind the mounting bolt would not cause the front of the case to crack like that, you would only get wear where your chair runs around the sprocket.
If I was going to reuse the case I would get it welded up, spaced right and do it properly, but I would look on Ebay and try to get a good second hand one that hasn't been damaged, I brought a inner and outer case off ebay for $100 and they were in perfect condition.
Another thing to think about is some poeple keep over tightening the centre bolt and not having the spacer right will warp the cases.

Ashley

RennieK · Aug 28, 2014

Just get a belt drive and open up that cracked area for ventilation. Put some stainless screen over it to keep the gravel out.

Also check out the MKIII mount stud. It is adjustable so tighten the inner cover to the engine then snug the support stud to the back of the chain case and tighten it down. Not really a big improvement UNLESS you are just buttoning down the outer cover and remember you forgot to shim it.

Bob Z. · Aug 29, 2014

Well, the clock idea sounded easy.
I'm sure this has been done before, and better.

Hobot · Aug 29, 2014

LOL! Now we are all impressed by your long term solution. Just needs the Green Globe logo somehow to finish it off : )

Nater_Potater · Aug 30, 2014

Bob Z. said:
Well, the clock idea sounded easy.
I'm sure this has been done before, and better.

Hey, I like that! You and Steve might just have a product there. How much do you want for it?

CanukNortonNut · Aug 30, 2014

Bob Z. said:
Looking at this primary inner case, is it salvageable?
Maybe it just serves as an example of what happens when the primary drive side is not adjusted properly.

The crack at the front mount was most certainly caused by not having a proper spacer/washer behind the chaincase center stud. Checking the flatness of the gasket surface shows a high spot.

More interesting is the drive chain wear pattern and the swing arm end plate wear in the rear of the case.
The steel sliding felt seal disc is worn through in an area, and the heavy chain wear indicates that without proper center stud alignment, tightening the primary cover nut will bend the whole primary case towards the drive sprocket.

This has all the earmark of the .125” shim spacer (item #34 part number 030023) being left out of the space where it should live between the top gearbox upper mount and the inside of the engine/gearbox cradle. Many times I have seen this very important shim spacer placed on the outside with the engine cradle after a rebuild because the DPO didn’t use the parts list book as an aid to reassemble the gearbox to the bike. What happens when you tighten up the top gearbox bolt (#33)? It shifts the L/H engine cradle over 1/8” more to take the space of the missing shim. This in turn pulls the inner primary over because its attached to the engine cradle with the chaincase center stud item #8 (060376) and either pulls the three mounting bolts out at the engine crankcase fixing points or cracks the inner primary case as in the top pic which then mashes the inner case against the swing arm plug. Hence the roundel tell tail insignia and chain gouges. This is why the chain is rubbing on the inside of the chain case. Little missed details create big problems.
http://www.oldbritts.com/1973_g7.html
Tom
CNN

Hobot · Aug 30, 2014

As mentioned prior this damage was d/t a hard crash impressing the peg into cover and impact pivoting on the center post to crack the front mount area. I don't think even w/o shims, tightening the center nut would not injure the front mount but could still strain case to allow chain to rub.

CanukNortonNut · Aug 30, 2014

hobot said:
As mentioned prior this damage was d/t a hard crash impressing the peg into cover and impact pivoting on the center post to crack the front mount area. I don't think even w/o shims, tightening the center nut would not injure the front mount but could still strain case to allow chain to rub.

NO Sir mr Steve
You wouldn't have the chain gouge at the inner primary caused by a laydown on the L/H side
I have seen too many missing shims as stated above. Measure the bottom bolt lug of a commando gearbox and what do you get? 3.30" and now measure the top Lug without the spacer? 3.175" there abouts!
Edit: if the shims were all correct and the bike gets lade down on its L/H side and damage is done to (first the foot peg hammering the outer case then the inner case would crack at the front as well as the center stud fixing stud area. Correct? If all the shims were there then something has to give, namely the inner boss for the stud hole would be cracked as well. Something Bob Z has to show in his pictures.

IMHO I don't think so.
Tom
CNN

Hobot · Aug 30, 2014

So many ways to mess em up. I've put inner cover on w/o shims and nipped tight to see a bit later the rear of case angled in but didn't pop the front mount. I've also crashed foot peg almost that bad into the cover with shims installed but it didn't hurt the front mounts. Some do some don't and some we'll never know.

Scrap primary inner case...

Bob Z.

Hobot

john robert bould

Hobot

Bob Z.

Biscuit

Bob Z.

Nater_Potater

L.A.B.

Moderator

Hobot

Biscuit

ashman

RennieK

Bob Z.

Hobot

Nater_Potater

CanukNortonNut

Hobot

CanukNortonNut

Hobot

Similar threads