MKIII Timing cover for 73 850 won't fit

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seanthomasking

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Has anyone had this problem? I have the kit from Andover, the lower right thread of the oil pump makes contact with the cover.

I tried on my old original one just for kicks and it fits straight over, but I noticed that the casting down the back where the thread on the oil tank is has a recess, where the MKIII cover does not & makes contact.

Has anyone machined this back to fit ? Any suggestions?

FYI I know all about the new bush and rubbers for the cover.
 
seanthomasking said:
I tried on my old original one just for kicks and it fits straight over, but I noticed that the casting down the back where the thread on the oil tank is has a recess, where the MKIII cover does not & makes contact.

Has anyone machined this back to fit ? Any suggestions?
Click to expand...

How does your Mk3 cover compare with these below?

grandpaul said:
MKIII Timing cover for 73 850 won't fit
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comnoz said:
MKIII Timing cover for 73 850 won't fit
Click to expand...
 
It doesn't have the extra hole. But that recess next to the very bottom timing hardware hole isn't machined back to allow for the bottom right hand pump thread, has anyone had this issue with a new MKIII timing cover before?

& if so machined it back?
 
seanthomasking said:
It doesn't have the extra hole.
Click to expand...

Ah yes, that particular cover of Jim's is a bit of an oddball as Mk3 covers wouldn't normally have that hole, but it seems the machining operation hasn't been done to your cover.
 
Not sure that the machined portion would be anywhere near the stud as they would be positioned 'inboard' of the oil pump feed bush and thus not not near the stud, an area where there would look to be no machining to take place - maybe it is the oil pump body fouling?
 
Madnorton said:
Not sure that the machined portion would be anywhere near the stud as they would be positioned 'inboard' of the oil pump feed bush and thus not not near the stud, an area where there would look to be no machining to take place - maybe it is the oil pump body fouling?
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It is the pump body, not the stud.
 
No no. I spoke to my old man yesterday, and he let me know that I might have an updated stage 6 oil pump? And that It definitely wasn't stock, as the studs extend past the oil pump body and my pump returns oil at a much faster rate than his stock MKIIA pump. (And the many nortons he has experience with).

The four studs that normally finish flush with the back plate of the oil pump, are actually 10mm past the back plate? Does anyone know of studs going through past the the back housing of this length?

I machined the cover down to pass the studs, which was very simple and non-treacherous.

Anyone have an idea?
 
It is the studs. They are 10mm too long and protruding past the body of the oil pump, this is why the new timing cover was making contact.

But is this normal, or aftermarket pump? as my oil pump returns oil much faster than others?
 
seanthomasking said:
No no. I spoke to my old man yesterday, and he let me know that I might have an updated stage 6 oil pump?
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I can't say I've ever heard of a "stage 6" oil pump, only '6-start' (gear) pump which was the standard pump/gear fitted well before the Commando (1966 from serial 116372)

MKIII Timing cover for 73 850 won't fit


seanthomasking said:
The four studs that normally finish flush with the back plate of the oil pump, are actually 10mm past the back plate? Does anyone know of studs going through past the the back housing of this length?
Click to expand...

"studs"

Screws? I can see no logical reason or purpose for them being that long.
 
seanthomasking said:
But is this normal, or aftermarket pump? as my oil pump returns oil much faster than others?
Click to expand...

Probably the only way to tell for sure would be to dismantle the pump and measure the pump gears.
 
To dismantle is a lot of work. Considering it pumps and returns at a very constant rate.. Is it possible the previous owner had the oil pump refurbished with longer studs/screws? And didn't cut them off flush with the pump body?
 
He might have said 6 start ?? This is uncharted territory for me, would the 6 start return oil more efficiently than he later commando's?
 
seanthomasking said:
He might have said 6 start ?? This is uncharted territory for me, would the 6 start return oil more efficiently than he later commando's?
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What the 6-start worm gear does is double the speed of the oil pump and this was standard on all Commandos (and other Norton twins from 1966) so 'early' or 'late' is basically irrelevant as all Commandos had the same oil pump.

If the scavenge pump happened to emptying a 'wet sumped' crankcase then it might give the impression that it was pumping more oil than usual?
 
So I'm guessing my oil pump screws/studs, are after market that the previous owner has mounted. You Never know what you buy from people these days... Could have cut them off.
 
The solution here is if someone can post a picture of the standard oil pump to illustrate what it looks like compared to what the OP has, I don't have a picture at the moment but could post one this evening.
 
seanthomasking said:
... Could have cut them off.
Click to expand...

Knowing what we now know :wink: that would have been the most logical course of action. :) :wink:


Madnorton said:
The solution here is if someone can post a picture of the standard oil pump to illustrate what it looks like compared to what the OP has, I don't have a picture at the moment but could post one this evening.
Click to expand...

https://www.google.co.uk/search?q=oil+p ... o+oil+pump
 
Madnorton said:
The solution here is if someone can post a picture of the standard oil pump to illustrate what it looks like compared to what the OP has, I don't have a picture at the moment but could post one this evening.
Click to expand...

That would be much appreciated. I would like to know what has been done to my pump &/or its origins
 
The previous owner had slot of abusive things done to the bike that I have found out over the years. This is another.

I have no idea if the studs through the pump are the right thread, or even for a Norton!!! Found many wrong threaded/length studs and bolts on the bike over the years and this seems to be another example.

The pump works very well, but I'm not over the moon about having to machine around 4 non-stock items in the pump body.
 
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