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I am fitting new pistons which are +20 to my 74 850 Commando. What is the end gap on rings supposed to be?
Thanks
Thanks
End Gap on Rings
- Thread starter thunderbolt
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A rule of thumb is 0.004" per inch of bore.
The Technical Data section of the 850-750 Commando Workshop Manual says:
Top ring fitted gap: 0.010"-0.012"
Middle ring (taper) fitted gap: 0.008"-0.012"
You might find a service manual useful for other information too.
Greg
The Technical Data section of the 850-750 Commando Workshop Manual says:
Top ring fitted gap: 0.010"-0.012"
Middle ring (taper) fitted gap: 0.008"-0.012"
You might find a service manual useful for other information too.
Greg
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The top ring gap should be at least as big as the minimum stated in the manual. There's no real maximum ring gap.
A second ring gap 30% bigger than the top ring gap is recommended nowadays.
A second ring gap 30% bigger than the top ring gap is recommended nowadays.
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Thanks guys for the replies. Will probably go with .012" top and middle ring.
I have lately seen some stuff written about installing the rings on the pistons into the cylinders dry with arguments for and against.
Any comments on the pros and cons???
Thanks
Don
I have lately seen some stuff written about installing the rings on the pistons into the cylinders dry with arguments for and against.
Any comments on the pros and cons???
Thanks
Don
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thunderbolt said:
All you'll get is more arguments for and against!
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concours said:
Dry ring assembly and hard-pulling first ride works well on my Triumph-engined Norton.
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Triton Thrasher said:
Thrasher can you explain more including the assembly process?
Thanks Don
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Has anyone seen this type of oil control ring before?
Are they any good?
Cheers Don
Are they any good?
Cheers Don
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thunderbolt said:
The assembly part is here:
https://www.rabers.com/technotes/general/piston_ring_installation.pdf
N
nortonspeed
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thunderbolt said:Has anyone seen this type of oil control ring before?
Are they any good?
Cheers Don
That looks like a GPM piston (Andover Norton stock these pistons nowadays instead of the original Hepolite pistons). Nothing wrong with that 2 piece oil ring (ring + expander) however I prefer the 3 piece oil ring (2 rings + expander) like the Hepolite 750/850 pistons. Better not use a 1 piece oil ring (without expander) as they are prone to let pass oil at high revs/compression.
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