Inner primary case got "chewed"

Nellie_Rocks · Feb 19, 2012

Hey All:

My chain parted and not being happy with that little piece of destruction it also decided to do this:

The chewed up piece is a splash guard and my question is, what are my options for repair? The casing is made from aluminum which I "believe" is difficult to weld. I have a shop guy on the Ranch that I work at and I'm hoping he can spot weld a thin piece of metal over the "chewed" area conforming to the arc of the splash guard. I'm not overly worried about appearances as when the primary case is back in place, you can't really see it AND my bike is not a show queen but a rider!

What do you guys think? Anyone had experience of this before?

Hit me with wisdom!

DogT · Feb 19, 2012

I'm sure it could be repaired by a competent aluminum welder. Just be careful not to warp the case.

Notice that round hole in the left of your picture? That's your spindle end rubbing on the case. It shouldn't do that. There should be clearance there, you might want to look into that. Check for the thick washer at the top left of the gearbox, inside the cradle. Item 34 here http://www.oldbritts.com/1971_g5.html

Dave
69S

Nellie_Rocks · Feb 19, 2012

Thanks Dave.

Yep, I did notice the spindle indent and have been reading posts about it and the chain rubbing marks. I'll check for the washer.

I was also wondering adding an extra washer to the primary chaincase center sleeve nut - on the outside of the inner chaincase, if that makes sense.

- Nells

grandpaul · Feb 19, 2012

Your primary concern (no pun intended) should be to first dry-fit the bare inner case with gasket and 3 bolts securing it to the crankcase, then measure the gap behind the center pillar bolt and install that thickness washer(s). ASSUMING your primary case isn't already warped and/or cracked at the mounting hole points.

If installing the appropriate spacer washers there still allows your chaincase to rub the swingarm, your isolastics are in wrong.

bwolfie · Feb 19, 2012

I have done this repair before. It is easy as long as everything is clean. I had a case with a chunk missing, cleaned, backed with a copper sheet and build up the missing area with welds. Grind to shape and good to go.

Hobot · Feb 19, 2012

Gosh I'm so sadistic to get some weird joy outta seeing someone's else's mess that ain't mine, whew.
Personally I'd just grind the edges to pleasing contour and leave it alone as ya can't see that part very easy at all and it don't really do much but genetic artifact for past ancient chain sling back in the Golden Era of forced economy that required constant oil flow chain cleaning sling -as properly provided for by Norton- that no one uses anymore, so w/o actually effective oiling flow - oil sling don't really occur forwards anyway due to the wind blast. You have rather more task to face to figure out and correct the alignment clearances and likely some resultant lurking uneven wear damage. Did your chain pass ya up like a mechanical robotic snake slithering past for a hound dogs head cocking confusion till lack of throttle effect ID'd the road critter?

rvich · Feb 19, 2012

If I were on the cheap side (oh wait I am!) I would go buy some epoxy and rebuild the area with that. JB Weld, Loctite and others make epoxies suitable for aluminum repair. No heat involved.

Russ

pdl999 · Feb 19, 2012

I noticed one day that my chain had three broken links. Turns out it had been rubbing on the primary case. The main cause in my case was gearbox misalignment but as has been pointed out already, the cause can also be incorrect shimming of the centre stud. Norman White told me chain rubbing is very common and I ended up taking his advice and converting to a 520 o-ring chain which leaves loads of clearance.

The point I really want to make here is that I heard some chain rubbing but chose to ignore it! I could well have ended up with a high speed breakage with catastrophic results! It's something all Commando owners should be aware of........

pete.v · Feb 19, 2012

Nellie_Rocks said:
I was also wondering adding an extra washer to the primary chaincase center sleeve nut - on the outside of the inner chaincase, if that makes sense.

- Nells

No!
This adjustment should be isolated to the inner primary to crankcase. You shim this center stud to bring the inner flush. If not flush with the cases, it will be warped when tightened and the outer will not seat properly. This will cause the primary to leak and more drastically bring about a false reed valve debate.

concours · Feb 19, 2012

That's an easy repair for a skilled weldor. A replacement peice can be cut/formed up from .125" Al, The inner primary can be laid face down on a flat table and restrained with clamps, TIG welded up nicely. Impurities in the castings may cause a sputter or three... but that non-critical appendage will be fine.

JimC · Feb 19, 2012

This will cause the primary to leak and more drastically bring about a false reed valve debate.

Why the sarcasm? Do you not believe that the stock Norton crankcases are pressurized? I think the only debate that exists is in your own mind. No one else seems to doubt the veracity and effectiveness of a depressurized crankcase. If you have a more effective way then a reed valve for accomplishing the evacuation of the crankcase, please let us know.

I see your avatar depicts a manual shutoff valve between the tank and the oil pump. Now that's debatable! That's one add-on you will never find on my bike.

Diablouph · Feb 19, 2012

Might be a good time to look into that French electric start. You get a new back primary with the unit.

pete.v · Feb 19, 2012

JimC said:
This will cause the primary to leak and more drastically bring about a false reed valve debate.

Click to expand...

Why the sarcasm? Do you not believe that the stock Norton crankcases are pressurized? I think the only debate that exists is in your own mind. No one else seems to doubt the veracity and effectiveness of a depressurized crankcase. If you have a more effective way then a reed valve for accomplishing the evacuation of the crankcase, please let us know.

I see your avatar depicts a manual shutoff valve between the tank and the oil pump. Now that's debatable! That's one add-on you will never find on my bike.

PM sent.

bill · Feb 19, 2012

not necessarily true. I have seen where the center posts that the stud passes through be to short. when this happens it can put to much pressure where the case halves seal and force the outer case inboard. there are some that recommend to shim the inner to outer on the center stud to achieve a .010 gap at the O Ring surface.

pvisseriii said:
No!
This adjustment should be isolated to the inner primary to crankcase. You shim this center stud to bring the inner flush. If not flush with the cases, it will be warped when tightened and the outer will not seat properly. This will cause the primary to leak and more drastically bring about a false reed valve debate.

bill · Feb 19, 2012

I am with Ludwig . WHERE DID YOU COME UP WITH THIS????

grandpaul said:
If installing the appropriate spacer washers there still allows your chaincase to rub the swingarm, your isolastics are in wrong.

pete.v · Feb 19, 2012

bill said:
not necessarily true. I have seen where the center posts that the stud passes through be to short. when this happens it can put to much pressure where the case halves seal and force the outer case inboard. there are some that recommend to shim the inner to outer on the center stud to achieve a .010 gap at the O Ring surface.

So you are saying that a somewhat negative bow, say .010, to bring the outer cover in home to the inner at the center nut?
That makes some sense but is also to say that shimming in this area has and should not have anything to do with clearance at the main shaft/sprocket area. Yes/no?

Hobot · Feb 19, 2012

Oh oh pvisseriii, I installed same valve about same area in the way of the KS lever if handle turned off, so guess I'm as mislead and you, ugh, just not on lowering case pressure any way ya can that don't take oil with it or clot up.

pete.v · Feb 19, 2012

hobot said:
Oh oh pvisseriii, I installed same valve about same area in the way of the KS lever if handle turned off, so guess I'm as mislead and you, ugh, just not on lowering case pressure any way ya can that don't take oil with it or clot up.

Ah yes, the thread robbing bate has been taken. I didn't think I would catch such a BIG one. You better be careful, though, there is someone very close who does not take to this sort of jocularity.

I been using this shut off for a few years now. It is routine and an ingrained habit. Just to be clear to those wondering, this is the feed line. If senility or Alzheimer's sets in, it won't matter anymore.

It's my bike, I do what i want.

Now, where were we.

bill · Feb 19, 2012

I did a correction in bold where I meant to say that the outer would put to much pressure on the inner. another point is IF the inner has had a lot of pressure put on it at the O Ring surface it COULD also bow it inward and cause it to warped at the central stud. That is where the shimming at the center stud comes in to play.

pvisseriii said:
bill said:

not necessarily true. I have seen where the center posts that the stud passes through be to short. when this happens it can put to much pressure where the case halves seal and force the inner case inboard. there are some that recommend to shim the inner to outer on the center stud to achieve a .010 gap at the O Ring surface.

Click to expand...

So you are saying that a somewhat negative bow, say .010, to bring the outer cover in home to the inner at the center nut?
That makes some sense but is also to say that shimming in this area has and should not have anything to do with clearance at the main shaft/sprocket area. Yes/no?

mikegray660 · Feb 19, 2012

pvisseriii said:
hobot said:

Oh oh pvisseriii, I installed same valve about same area in the way of the KS lever if handle turned off, so guess I'm as mislead and you, ugh, just not on lowering case pressure any way ya can that don't take oil with it or clot up.

Click to expand...

Ah yes, the thread robbing bate has been taken. I didn't think I would catch such a BIG one. You better be careful, though, there is someone very close who does not take to this sort of jocularity.

I been using this shut off for a few years now. It is routine and an ingrained habit. Just to be clear to those wondering, this is the feed line. If senility or Alzheimer's sets in, it won't matter anymore.

It's my bike, I do what i want.

Now, where were we.

you sir are an upstart! and i shall have to PM you to remind you so! :mrgreen:

Inner primary case got "chewed"

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