Inner primary modification, why?

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Saw this inner primary on Ebay, the curved rib on the back has been ground off and I'm wondering what the reasoning would be for this modification? Weight saving measure?


Inner primary modification, why?
 
Probably partially broken off by a flying chain and then tidied up by someone afterwards.

I guess it could also have been to have allowed the fitment of a super sized sprocket perhaps?
 
That makes sense. Do you think it makes much difference to the rigidity of the housing?
 
Doubt it would make much difference to rigidity
It's easy enough to weld it back on as long as you don't distort the case with heat
 
I have an inner cover I won't use because that is broken off. My thinking is that if a chain breaks, it is less likely to damage more important things if it has that to break off! It's also nice to not have crap flung on the engine (any you).
 
I added a sheet metal shield to the inner primary cover of my Atlas. No more oil mess from chain lube, or the oil mist from the oil tank vent, all of which would end up on the drive side of the crankcase. I am sure that is the purpose of the ring on the Commano inner cover.

Slick
 
Mine broke at a very young age when I threw a chain doing a burn out in my younger days, when I convered my Commando to the Featherbed frame and rebuilt the motor for it I grounded that off completely, I run my oil tank and crank breather hose into a large catch bottle in between my engine mounts and I only lube my chain when needed, I don't get much crap spraying onto my motor at all and its been like that for over 37 years now, it also makes it easier to check your front sprocket or putting a new chain on without that cover part.
A few years ago my chain threw a retaining clip and my chain got jammed up between the inner case , it was easy to unjam it but if the cover was still there it would have been a major job to free it up on the side of the road and the funny thing was the spare retaining clip I had on my clutch cable thats been there for over 40 years was the wrong size clip for my Norton chain, lucky I wasn't to far from home lol.

Ashley
 
Broken chain is probable cause. It is the first line of defense to the chain whacking the engine. If it is cheap then buy only if you have skills to re-fab the surround , but keep looking if you need the inner primary without skills. You could make a piece from a 1/8" flat plate aluminum with tabs bent at ninety for screw holes or a weld up to mimic the original profile. It is probably more work than worth.
IMHO, Keep looking.
Cheers,
Thomas
 
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I believe that if you run a larger than 22 tooth gearbox sprocket, you have to remove the cast in chain guard from the inner primary.
 
When I bought my Commando in '06, that reinforcement rib had been about 1/2 ground away by the chain anyway. ;) If the transmission/chain/sprockets/swingarm are not precisely aligned, it is easy for that to occur.
 
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