Primary chain case damage

MikeM · Sep 30, 2016

Notice this today while I was cleaning things up for storage. Looks like this must have happened to the prior owner? I dont recall any bad noises or bits flying off. I would imagine this would have made quite the noise and am assuming the drive chain most likely broke at some point?
Thoughts?
Photo is of the top of the inner primary just above the front sprocket,at the rear of the cover, looking down from the top.

Nater_Potater · Sep 30, 2016

'Shouldn't be a problem as far as functionality is concerned. I'm surprised you don't get chain lube slinging up and forward from there. You do lube your chain, don't you? :wink:
The only thing that comes to mind is the Salt Flats, as they're very picky about how the chain is covered (for safety issues).

Nathan

Danno · Sep 30, 2016

Looks like it spit the drive chain at some point. Happened to me once when a master link clip let loose. I was luckier than you and mine just ran out the back and ended up on the road with no damage. I would take a strip of sheet aluminum and epoxy it over the gap to keep things clean until you have to pull he primary for some other repair when it can be fixed properly.

MikeM · Sep 30, 2016

Danno said:
Looks like it spit the drive chain at some point. Happened to me once when a master link clip let loose. I was luckier than you and mine just ran out the back and ended up on the road with no damage. I would take a strip of sheet aluminum and epoxy it over the gap to keep things clean until you have to pull he primary for some other repair when it can be fixed properly.

I was wondering about putting some type of plate over it. JB weld I guess. It had to have happened before I got it.
I dont think I will have to worry about taking it to Bonneville.

1973x75 · Sep 30, 2016

Mine is like that too. Previous owner used a strip of sheet metal and tapped a couple of screws into the aluminum to hold it in place.

Craig · Sep 30, 2016

Be careful with whatever you use to make a fix .... you don't want loose items dropping in and getting caught up in the chain , rotor /stator etc. .... gets expensive in a hurry ....
Craig

BillT · Sep 30, 2016

I took mine to a local welder - he welded in a new piece of aluminum and bead blasted it - can't tell there was ever a break

(about $40

)

norton73 · Sep 30, 2016

I know of a rider who had his battery hold down get loose and drop down there. It jammed up the chain and broke the cover similar to your pic.

MikeM · Oct 1, 2016

Craig said:
Be careful with whatever you use to make a fix .... you don't want loose items dropping in and getting caught up in the chain , rotor /stator etc. .... gets expensive in a hurry ....
Craig

Thats great advice. Any ideas on the best way to repair it on the bike? I dont want to tear it down at this point.
Epoxy a plate over the top?
Thanks

Hortons Norton · Oct 1, 2016

I think that if you never knew it was like that to begin with maybe just leave it, I don't think it will hurt anything. Next time you have it off fixing it right will be much easier and will be a proper fix. Just my opinion. :wink:

AltaNorton · Oct 3, 2016

BillT said:
I took mine to a local welder - he welded in a new piece of aluminum and bead blasted it - can't tell there was ever a break

(about $40 )

The same thing had happened to me years ago, but the chain cover was almost completely broken off on mine. You might be able to make it out in this photo, as you can see the chain completely wrapping around the countershaft sprocket.

Once I started my restoration, I took it to a local welder/fabricator and he fixed it up to look brand new. It shouldn't be too hard for any decent welder to patch up and make look good. I may have got dinged for more than $40, but it was worth it.

Matt

Craig · Oct 3, 2016

My old chain case was broken like that when I got bike ..... it had been epoxied to fill up most of missing piece .... was like that until alternator ate itself several years later due to unrelated issue , reused tab washers inside case one too many times ....anyway from look of that I would either leave it be or try a patch fix , until you feel like spending some cash ....
Craig

Towner · Oct 3, 2016

Mine has the same damage. I don't know what the cause is either. I leave it as it is. It don't bothers me much, no chain lube comes out and it is not very conspicuous. Perhaps I buy a new case when I have to much money.

Ralf

ashman · Oct 4, 2016

Its a comon thing that it breaks there, its doen't realy do much at all mines been broken for some years now from a lose chain or broken chain, I still use lube on my chain but haven't found it to splash all over my motor or any other diffrents, and when I installed my belt drive many years ago and installed a extra ajuster I ended finding it was easier to ajust the extra ajuster with that peice broken off.

Ashley

grandpaul · Oct 5, 2016

Very common damage; I've had my welder fix up at least a handful done very similarly by blown chains.

This one was badly mangled, so I just sliced off all of the damaged area

I provided the welder with an 8" long strap of thick aluminum and he did the rest...

MS850 · Oct 5, 2016

My MK3 had a broken primary inner cover that I discovered when restoring, the PO repaired it with JB Weld. It looked fine so left it.

At least if the chain breaks this doesn't happen, I found this hole when restoring my '76 CB750. I repaired it without splitting the case.

Primary chain case damage

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