Oil Pump drive gear nut

Status
Not open for further replies.
Satan's Aardvark

Satan's Aardvark

Joined
Jan 26, 2021
Messages
44
Country flag
I'm replacing the oil pump on my '72 750. Badly worn.

What is the correct spanner fit for the drive gear retaining nut?

None of my whitworth or AF fit, 14mm is close but I'm guessing it's not an exact fit.
 
Good question!
I have just measured the nut on my 650ss (only thing at hand) and it's 13.28mm across the flats.
None of my spanners fit either (AF, Whit or Metric)
Ahhh - just use a shifter!;)
 
Satan's Aardvark said:
What is the correct spanner fit for the drive gear retaining nut?

None of my whitworth or AF fit, 14mm is close but I'm guessing it's not an exact fit.
Click to expand...

The nut is 3/8" UNF, therefore, the hexagon should be 9/16" AF (0.563")...
andover-norton.co.uk

Andover Norton - NUT 3/8

NUT 3/8
andover-norton.co.uk

The next size smaller would be 14mm (0.551"), then 1/4"W (0.525"/13.34mm), then 13mm (0.512").

Spanner Jaw Sizes

Useful guide on spanner to nut/bolt relationships, and the selection and use of spanners and socket sets
www.crawford-space.co.uk

robs ss said:
I have just measured the nut on my 650ss (only thing at hand) and it's 13.28mm across the flats.
None of my spanners fit either (AF, Whit or Metric)
Click to expand...

The 650SS nut is likely to be BSC so 1/4"W (13.34mm) should be the correct spanner size.
 
Thanks for the replies.

Not sure what mine is, 1/4 WW is too small, 9/16 AF is too big. It may be something odd as the engine has been rebuilt before my time.

Perhaps a unique shifter size as Rob says.
 
When I first got my Rickman I tried to take out the sump drain plug. Way too small for the correct Whit socket. Puzzled! Got in close with a light and vernier and it was clear what happened: somebody had taken a file to the hex and brutally reduced it to
3/4" AF! I guess in the 70s there were a lot of bike owners who ether were skint or simply too dense to buy a few tools. It really was tough for a young guy to operate in those pre-internet days when good information was like gold. Imperial stuff was not common in the states during the Dark Ages of British Motorbikes!
 
Satan's Aardvark said:
Thanks for the replies.

Not sure what mine is, 1/4 WW is too small, 9/16 AF is too big. It may be something odd as the engine has been rebuilt before my time.

Perhaps a unique shifter size as Rob says.
Click to expand...
Sometimes, if you can't find the "correct" spanner there will always be a Metrinch one that will fit (and do less damage than a slightly loose conventional spanner)
The only downside with them is the "wasted throw" phenomenon due to them being an initially loose fit. Great otherwise.
 
Last edited:
Satan's Aardvark said:
Thanks for the replies.

Not sure what mine is, 1/4 WW is too small, 9/16 AF is too big. It may be something odd as the engine has been rebuilt before my time.

Perhaps a unique shifter size as Rob says.
Click to expand...
The Metrinch 14mm&9/16 fits my 13.28mm well so will work on yours - given that 9/16 is too big👍
If you have not seen them their "wave" profile engages the centre of the flats instead of the corners (which conventional spanners do)
 
robs ss said:
The Metrinch 14mm&9/16 fits my 13.28mm well so will work on yours - given that 9/16 is too big👍
If you have not seen them their "wave" profile engages the centre of the flats instead of the corners (which conventional spanners do)
Click to expand...
I think some American cowboy outfit from Kenosha WI call it 'Flank Drive'
 
robs ss said:
Sometimes, if you can't find the "correct" spanner there will always be a Metrinch one that will fit (and do less damage than a slightly loose conventional spanner)
The only downside with them is the "wasted throw" phenomenon due to them being an initially loose fit. Great otherwise.
Click to expand...
Always keep a small set of Metrinch combination spanners in the toolbox, rarely use them, but when you have a tricky size they are very useful.

Also called 'wall drive'
 
Metrinch???
I thought it was a typo...
Interesting, I have seen them, didn't know what they were called.
metrinch.tv

Metrinch

Metrinch.TV
metrinch.tv
 
Last edited:
robs ss said:
The Metrinch 14mm&9/16 fits my 13.28mm well so will work on yours - given that 9/16 is too big👍
If you have not seen them their "wave" profile engages the centre of the flats instead of the corners (which conventional spanners do)
Click to expand...
Thanks Rob

I do have those too, not metrench but some other manufacturer, and I expect they'd do the job without any issues.

Some wear is evident so I've decided to replace the gear and retaining nut anyway.

My verniers need a new battery, so unable to measure the exact width ATM but it's somewhere between 13 & 14mm.
 
Status
Not open for further replies.

Similar threads

S
  • Locked
AMR oil pump cure
2 3
Replies
46
Views
5,801
kommando
kommando
ES234
  • Locked
Oil pump scavange gear question
Replies
16
Views
2,482
ES234
ES234
ES234
  • Locked
Oil pump return gear identification
Replies
1
Views
841
gortnipper
gortnipper
Britstuff
Norton Dominator timing cover fit problems. Recess for oil pump seal too shallow?
Replies
7
Views
1,424
mean gene
mean gene
D
  • Locked
How to tighten the oil pump shaft lock nut?
2
Replies
23
Views
4,976
concours
concours
Back
Top