crank bolt torque (2021)

The early factory Commando manual says to "make sure they are very, very tight".

"Tighten until it snaps off, then add one quarter turn"

Onder said:

"Tighten until it snaps off, then add one quarter turn"

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No..... then BACK one quarter turn

pdf p. 22

"CRANKSHAFT
Disassembly and Assembly
.
5. Nuts are torqued to 35 ft lbs on 750s and 30 ft lbs on 850s."

robs ss said:

For the average "home wrenches" like me, it can be hard to trust your sometimes educated hand.
I believe in using a good torque wrench (or equivalent - say spring balance and drilled spanner) whenever you can.
The result has to be better in the long run.

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If I have created any misconception that I am in any way anti torque wrench, then let me correct that immediately !

Of course, every motorcyclist should own one or more (for different ranges) torque wrenches and, as you say, use them whenever they can.

I’ve got a few, my favourite is a rather expensive Japanese dial gauge type as used by automotive OEMs. It’s in Newton Metres so I have to use a conversion table, but it’s worth it, the long handle and large dial make it very easy to control the torque very nicely. I only use a break-back (click type) in areas where looking at the gauge isn’t easy.

However, with fasteners where a torque wrench is not possible, it is really not difficult to practice with a nut and bolt, practice tightening and check with a torque wrench, it doesn’t take long to get a reasonably accurate feel. Then do you your hard to get at fasterners.

Some people do make very clever and accurate tools and adaptors etc to enable use of a torque wrench with such hard to access fasteners, and more power to them. But my guess is that for most “home wrenches” attempts at making and using such home made devices would most likely lead to greater error than a practiced ‘feel’.

Thats what works for me at least.

L.A.B. said:

http://technik.doc.free.fr/Norton/Norton_and_Hybrids_1966_1976_WorkShop_Manual.pdf

pdf p. 22

"CRANKSHAFT
Disassembly and Assembly
.
5. Nuts are torqued to 35 ft lbs on 750s and 30 ft lbs on 850s."

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So, we have documented figures of between 20-35ft lbs...

We don’t need accurate torque wrenches... we need psychic torque wrenches !!

This is the book I’m referencing (can’t recall if it was from AN or RGM):

Thanks to all for the input. Think I have it sorted now. The confusion was simply a change in thread form to UNF. My factory book says "850 & 750" but does not mention bolts at all. No doubt they expected everyone to go to studs and nuts.
Mystery solved!

Fast Eddie said:

It’s not hard to learn to get a feel for that kind of torque. Especially when you’ve done the hundreds, perhaps thousands, that Mick has!

I don’t recall reading lots of horror stories of engines failing due to these fasteners failing...

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Perhaps I should add that when I spoke to Steve Maney about the crank bolts in one of his cranks, he is from the same school of thought.

The only concern he had was that since I have a pair of extended spanners for this job, they should not be too long!

A bodger will always have an excuse to bodge something and you will never remove the bodge from a life long bodger.

I will stick to my dodgy ways.
Cylinder head fasteners = all torqued.
Cylinder base fasteners = all torqued.
Crankshaft fasteners = all torqued.
Cradle to engine case fasteners = all torqued.

Do I torque all fasteners on a bike, no.

So... Mick hemmings and Steve Maney are bodgers...?

I can't comment regarding those professionals, I am just a boilermaker/welder in a garage who took the time and the time could be a $5 ring spanner cut in half with a socket for the drive welded on one end. (which anyone could do or have done cheap as chips)
I would regard it if true as poor advice.
#
"The only concern he had was that since I have a pair of extended spanners for this job, they should not be too long!"

".I never bother with a torque wrench on these, because unless you've got proper adaptors and things to get at the bottom ones I can't see the point of it. So the trick is just to use two good spanners,-and tighten them up."

As I said earlier, until I hear all the stories of engine blow ups due to under or over torqued crank fasteners, I’ll save my worry energy for something else...

I would venture to suggest that the VAST majority of Commando‘s on road and track have crank fasteners that have been tightened following Mick’s “bad advice” and that none have failed as a result.

As I said earlier, for those who have the ability and inclination to make special adapters, more power to them. But that simply does not mean those that don’t are doing anything wrong!

So you are saying if you had the tool to do it properly you would not use it, fair enough.
#
It has nothing to do with worrying just doing things in a tradesman like manner and in this case that is easily done as proven.

My book might arrive this week, I pin my hopes on Mr White.

Time Warp said:

My book might arrive this week, I pin my hopes on Mr White.

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What for? To support your point of view?

You may notice that most spanners available today to fit the crank nuts are rather short and pretty much all the ring spanners need grinding for clearance. So to be described as a 'good' spanner in this case they need to be specific to the job. Don't go imagining I am using 3 foot long spanners,

They are about 9" long so that I can get a decent hand grip for all of the nuts. I have had to prepare another set since I have moved (as Steve did) to ARP nuts.

What percentage of the time is your crank spinning above 6000rpm?

I made a special picture.

Or.

Its not a point of view, I just enjoy building engines (including for other people since the 1980's)
Even if it was proven to not matter, I will always torque critical fasteners.

Edit
This arm is only to get to the two fasteners that are not directly accessible. The other four crankshaft fasteners are in the open so easy to get to with a torque wrench.

They have probably been using the same nuts and bolts for last three rebuilds also, don't waste your time.

Hortons Norton said:

They have probably been using the same nuts and bolts for last three rebuilds also, don't waste your time.

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Studs yes, nuts no, as I said I changed to ARP. I called the man who made the crank and asked for a nut and stud set, he said why? are they damaged?

L.A.B. said:

The early factory Commando manual says to "make sure they are very, very tight".

http://britmoto.com/manuals/Manuals/Comm_man.pdf

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Oooh man, I really like that!!