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stud sizes

Submitted by patrick_ward on Friday, 23 October, 2020 - 21:43
Forums
Commando

I have a 850 electric start engine,I want to clean out the threads on barrels,the (2 small studs at front off engine )can anyone shed some light on the size of tap to clean them up.also the sizes for the head studs,thanks 

Submitted by grant_tiller on Friday, 23 October, 2020 - 22:16

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For the barrel:

  • The two wasted studs are 3/8" UNC (16tpi) and 5/16" UNF (24tpi)
  • The centre stud is 3/8” UNC (16tpi) and 3/8” UNF (24tpi)
  • The four long allen cap bolts are 3/8” UNC (16tpi)

You can find a diagram showing spanner sizes, torque and tightening order here:

https://granttiller.com/norton-commando-cylinder-base-tightening-sequence-and-torque

For the head:

  • The four outside bolts are 3/8” Cycle Thread (26tpi)
  • The three larger studs are  3/8” BSF (20tpi) and 3/8” Cycle Thread (26tpi)
  • The two small studs are 5/16” Cycle Thread (26tpi) at both ends
  • The single bolt is 3/8” Cycle Thread (26tpi)

You can find a diagram showing spanner sizes, torque and tightening order here:

https://granttiller.com/norton-commando-cylinder-head-tightening-order-and-torque

 

I think that covers it!

 



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