Questions? Looking for parts? Parts for sale? or just for a chat,
The WD Motorcycle forum
Aloha everyone,
It's been a while and some of you may or may not remember me from previous posts, questions and discussions. None of you probably remember that for quite some time me and my bikes has lived on different sides of the country, 50 km apart.
Well, that has now changed and we all live close to each other!
So today I started sorting out the last little details on my -47 M21 before I will start riding it. Number one was a loose clutch nut. I am talking about the small one inside of the spring, the one that holds the basket on to the taper. It was all loose and wiggly and the bowler was scratching the tranny-cover.
Now to what torque is this nut to be tightened?
I had a look around the tech-section but failed to find the answer, maybe I was blind. If there is not a defined torque any rough approximation by at knowledgable person would be appreciated. Kinda boring nut to have go undone while riding.
Best regards,
Simon
It happened to me once. I used Loctite thread locker and my battery operated rattle gun, it's been fine ever since. Torque settings weren't really detailed back then. Ron
email (option): ronpier@talk21.com
I don't have a torque figure for that one...Torque figures, such at those I use for the head bolts, I arrived at by a combination of experimentation and looking at the torque figures for more modern bikes with the same diameter head bolts as a rough guide...
So, if you started off with the clutch nut torque figure for say, an A65 or T140 you might be in the right area...
I do it up (very) tight with a socket and T Bar whilst applying the rear brake to stop it moving (with the bike in gear.)...I've not had one come undone yet. I don't use Loctite....
You can apply plenty of force as both the shaft and the nut are hardened...Ian
email (option): ian@wright52.plus.com
Thanx Ian and Ron!
Googled and found the number 80lbft -dear lord!
I cant remember but I suppose that's what I tightened the clutch nut on my Bonneville to as well.
This one now is at about 30-40 lbft, we'll se how it goes...
/Simon
I'd have thought 80ft/lbs a bit high...but that's only a gut feeling...
There are no torque figures for the M20 as they pre date the general introduction of the 'modern' torque wrench, so any figures on the internet for a given application aren't BSA figures and should be approached with a 'critical eye' and a sensible level of caution and analysis...Ian
email (option): ian@wright52.plus.com
Same gut feeling among us then Ian.
And yes I know about the torque figures being of later dates. I once saw a 45 minutes film from the Triumph factory that now seems have disappeared from the internet. Anyway, in the film the process of building the 500 OHV twin was thoroughly explained and not a torque wrench in sight in the entire factory.
/Simon
I do not have a modern torque wrench. :wink:
[.. Good fitters would know how far to tighten a bolt nut or stud up to its correct torque just by feel. You can have 2 exact size studs and nuts but made of a different grade of steel and hardening and the torque figures for these will be completely different...']
Those two statements rather contradict each other I'd have thought...How would a fitter picking up a bolt know what steel it was made of etc.?...And if he didn't know how would he then know how much to tighten it?...
It is certainly true that you develop a feel for when a bolt is at the point where it begins to stretch (prior to ultimately snapping) or when a thread is in a similar condition (prior to stripping). However, I don't think anyone could do up a bolt, or particularly a series of bolts, to a specific torque entirely by feel..I've spent most of my life in engineering and I'm fairly sure I couldn't do that....
In the case of M20 head bolts for example it is difficult to do up all 10 bolts to exactly the same tightness, particularly if a composite head gasket is used which by it's nature has some misleading 'give' in it as it is tightened...
There is also the facet of human nature that dictates you will probably give the bolts a little extra 'tweak' rather than risk them not being tight enough...
Personally, I always use a torque wrench to get an evenly applied 28-30ft/lbs on the head bolts...Single fasteners or fasteners where even tightening is not so important I do tighten by 'feel' but I have no idea how many ft/lbs have been applied....Ian
email (option): ian@wright52.plus.com
The old school mechanic in the Garage workshop where I trained as a motor mechanic would continually say "Tight is tight" Anything over that and you're probably stretching the threads. Like Ian, probably one of the few times I use my torque wrench is on the head bolts, which is more about getting them tightened evenly. Ron
email (option): ronpier@talk21.com
I can't argue with that..As it happens I followed a very similar trajectory, starting my apprenticeship in 1970 with Brown and Sharpe, the machine tool manufacturer...
Unfortunately, all the 'apprenticeship tools' I made were stolen along with a lot of other stuff when someone broke into my garage in the late 70's...
I have a couple of torque wrenches but only really use one for the BSAs...That's a 0-50ft/lbs one that I purchased specifically to tighten M20 head bolts as I felt I wasn't doing a good enough job 'free hand'....
The 1970 Triumph T120R that I built a couple of years back had quite a few specified torque settings and I tended to follow those as I didn't really see a reason not to whereas I haven't used one at all on the Gold Star I've just finished....
As the bulk of the bikes I've had were from the 40's through to the early 60's (the end of pre unit in BSAs case) torque wrenches haven't figured that much over the years and I have relied mainly on experience and 'feel'.
Twin cylinder big end bolts and a few fasteners on the Square Four were notable exceptions...
Regarding the accuracy of torque wrenches I tend to accept that if they aren't old and have been treated well, they should be reasonably accurate...When I worked at British Aerospace for example, everything was subjected to testing and calibration on a regular basis but I guess in the private workshop you have to stop somewhere!! :laughing: ...Ian.
email (option): ian@wright52.plus.com
email (option): moatjon [ at ] aol.com