Crankcase torque settings

Status
Not open for further replies.
danfr

danfr

VIP MEMBER
Joined
Oct 17, 2012
Messages
138
Country flag
I’m just about to reassemble my 71’ 750 crankcase halves and am looking for the torque settings. I do see 25 ft/lbs for engine mounting bolts which sounds about right.

But what about the 5/16” and the two cheese head screws at the bottom? I was planning on doing 20 for the 5/16” but would love some direction.

Cheers
Dan
 
The torque link is a good one; my only suggestion is that the "NOTES" at the very end of the specs/explanations should be at the very beginning.
 
<Lubrication makes bolts easier to turn and therefore lower torque should be used>

OK but by how much?
 
Depends on the lubricant. Has a surprisingly significant effect:

Reduced Torque with Lubricated Bolts

Lubrication effect on bolt tension and torque.
www.engineeringtoolbox.com www.engineeringtoolbox.com
LubricantTorque Reduction
(%)
Graphite50 - 55
White Grease35 - 45
SAE 30 oil35 - 45
SAE 40 oil30 - 40
No lube0
 
Onder said:
<Lubrication makes bolts easier to turn and therefore lower torque should be used>

OK but by how much?
Click to expand...
Too many variables to give a concrete answer. Thread pitch, thread count, thread angle, materials and much more all play into it. Most Norton engines have lots of helicoils, IMHO do to the stupidity of using fine threads in the alloy castings. I do say this in the document:

Plated Steel or Stainless Steel screws in aluminum casings require great care if fine thread. 5 ft lb. with anti-seize is fine with course threads but is probably too much with fine threads like those used for the gearbox. I always use anti-seize on Stainless into aluminum but only 4ft lb (48 in lb.) for fine threads.

I used a broken set of Norton cases to test. Stainless 1/4" cap screws with Nickel anti-seize stripped the case every time at 6 ft. lb. At 5 ft. lb. they sometimes stripped. At 4 ft. lb. no problem. Doing the same test with Triumph cases (course threads), 8 ft. lb. striped every time, 7 ft. lb. and 6 ft. lb. sometimes, and 5 ft. lb. never. Since I always use nickel anti-seize on fasteners going into alloy, I didn't bother testing without.

One "how much?" example is the exhaust nuts. If you tighten one fully, mark the nut and the head, unscrew and put a small pea sized and amount of Nickel anti-seize on the threads and tighten to your old mark. You'll find that pulling as hard as the first time will turn the nuts about 1/4 turn more and the nuts once re-tightened hot will be unlikely to come loose.
 
I ended up doing 25ftlbs and 20ftlbs in the 3/8th and 5/16th respectively. Which is a little on the higher end according to the link but I would imagine will be fine.

I used the RGM stainless hardware with stainless nylock nuts. I’m hoping they’re somewhat higher tensile than your traditional stainless steel. Otherwise, why would they sell a kit like that?

I installed the hardware dry with the exception of the two cheese heads that bolt directly into the cases. I used some blue loctite on those guys.
 
danfr said:
I ended up doing 25ftlbs and 20ftlbs in the 3/8th and 5/16th respectively. Which is a little on the higher end according to the link but I would imagine will be fine.

I used the RGM stainless hardware with stainless nylock nuts. I’m hoping they’re somewhat higher tensile than your traditional stainless steel. Otherwise, why would they sell a kit like that?

I installed the hardware dry with the exception of the two cheese heads that bolt directly into the cases. I used some blue loctite on those guys.
Click to expand...
Stainless on stainless dry is a bad thing!

1) You have no idea how tight you've actually made them, see this: https://www.fabory.com/en/knowledge...teel/the_seizing_of_stainless_steel_fasteners
2) If they seize on the way in, they are VERY hard to get apart.
3) They will become "one" soon! Hope you never need to take it apart again!
 
  • Like
Reactions: baz
I went back and added blue loctite to all the nuts and retorqued to the same previous valves. The nylock is kinda a one shot deal but I figure re using them with the loctite should suffice.

It easy to go down the wormhole with these commandos. I try not to overthink. Bolt on and move on.
 
Mart UK said:
Shouldn't the nylock prevent that?
Click to expand...
No. You still have thread on thread action which can gall.

Crankcase torque settings
 
Mart UK said:
Shouldn't the nylock prevent that?
Click to expand...
A good thing to remember with nylock nuts is that they are meant to be used once. They lose their locking characteristics after it’s first use.

Cheers
 
Sorry to sound like a broken record here Dan! But I’d have used copper grease. Those nuts require checking regularly especially after the first build. As paint squashes and settles etc they need nipping up to take up the slack. I never thread lock things that need a regular nip. If you don’t take care with this, you could end up back where you started with a bust case.

And BTW, nylon nuts can be re used, they might not have the full grip they have from new, but they still have enough to prevent loosening even after several uses in my experience.
 
In my experience nylocks don't keep a nut tight
They do stop you losing the nut but that's about it
 
Status
Not open for further replies.

Similar threads

F
Torque Settings
Replies
3
Views
262
Flatbattery
F
Bonzo
What would be the torque setting for....
Replies
6
Views
432
Ron Hulton
Ron Hulton
mrlsi
  • Locked
Torque setting
Replies
18
Views
2,991
guest76
G
P
  • Locked
Torque setting and measurement
Replies
6
Views
1,052
L.A.B.
L.A.B.
Lineslinger
  • Locked
If I over-torque by....
2
Replies
30
Views
6,179
Ratboiler
R
Back
Top