Author Topic: Primary chaincase screw sizes  (Read 236 times)

Offline Mosin

  • A's Best Friend
  • ***
  • Posts: 245
  • Karma: 2
  • Cumbria
Primary chaincase screw sizes
« on: 16.12. 2018 11:19 »
Quick question: I am aware that two different diameters of machine screw are used to hold the primary case to the inner. The majority are smaller diameter of various lengths, but there are also three larger ones towards the front of the bike which go right through the primary inner and screw into the actual crankcase itself. Does anyone happen to know the size/dimensions of these three larger screws?

Thanks
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Posts: 7728
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Primary chaincase screw sizes
« Reply #1 on: 16.12. 2018 19:03 »
G'day Mosin.
42-7517 is 5/16 x 1-15/16 whitworth but I'd double check the length as if too long it will foul the crankshaft web.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Mosin

  • A's Best Friend
  • ***
  • Posts: 245
  • Karma: 2
  • Cumbria
Re: Primary chaincase screw sizes
« Reply #2 on: 17.12. 2018 17:53 »
Just the information I Was needing. Many thanks!
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England

Offline Colsbeeza

  • A's Best Friend
  • ***
  • Posts: 177
  • Karma: 2
Re: Primary chaincase screw sizes
« Reply #3 on: 17.12. 2018 23:19 »
Hello Mosin,
Roger SB did a great job on this some time ago.

Check out  -  https://www.a7a10.net/forum/index.php?topic=13099.45

I have attached Rogers sketch, which shows lengths. I went through this a few months ago, and found Rogers sketch was spot-on.
Cheers
Colin
Colsbeeza
Australia

Offline a

  • Valued Contributor
  • ****
  • Posts: 274
  • Karma: 4
Re: Primary chaincase screw sizes
« Reply #4 on: 18.12. 2018 00:38 »
https://mikesclassiccyclespares.com/product/42-7517/
These are genuine BSA NOS ones if you'd like??