Fitting a Triumph clutch is becoming a popular option when the old single spring units wear out.
I have fitted a couple of Triumph clutches lately and have encountered a problem with the clutch spring screws that is worth a mention.
The head of the screw has a small 'bump' pressed into it, to provide a self locking function.
This protrudes under the head of the screw and comes up against the end of the spring coil when the screw moves in an anti clockwise direction..preventing any further loosening.
However, pattern spring screws have this bump too heavily pressed in, making it too large. So, they do up without any problem but when an attempt is made to undo them the bump locks against the spring end and will not ride over it.
The only solution is to force them undone, as with the screw fitted all the way in the end of the spring is recessed into the clutch pressure plate and is not accessible.
Not only is this very difficult but it 'unwinds' and stretches the spring making it unfit for further use.
The solution is to dress the lump down with a file..a small,curved 'riffler' or 'rat tail' file is the best one for the job...or some careful work with a 'Dremell' or die grinder as an alternative.
Material should be removed from the side that fits against the spring when the screw is being undone to eliminate the problem, but take care not to overdo it.Aim to maintain most of the hieght of the bump but to create a smooth, curved surface which will ride over the spring easily as pressure is applied when undoing.
While on the subject of the Triumph clutch if you decide to fit one there are two types of cluch spring available..a heavy gauge short one and a lighter gauge long one...specify the longer, lighter spring when ordering parts for a nice light clutch action...Ian

email (option): ian@wright52.plus.com

Hi ian

When i ran my triumphs (3t's) and if or when clucth springs needed adjusting, i used a small penknife blade placed between the spring & brass adjuster

This allowed undoing of the adjuster without spring or adjuster damage

Nice clutch the triumph one !!

Where can you get the shaft converters ?

Jo'b

email (option): Jonnyob1@googlemail.com

I have a new three spring TRIUMPH clutch fitted to the HM21.I too had a problem with these parts also the springs I replaced both with genuine old stock TRIUMPH parts! problem sorted, must admit these are a excellent clutch I also have one fitted to my 1950 ZM20 this has been on there for 35+ years and still needs no attention.I will also fit one to my WM20 & B33 when I find the funds..Dave.

Has anyone gone the way with the racing clutches? My Norton clutch is sometimes problematic, not so bad as on the M20's mind you, but still it could be better.

Last weekend I talked to a guy selling these racing clutches, while not cheap at around 400 quid, they look very promising, there is a type that bolts straight to the Norton gearbox, and even a belt drive is possible, but twice as expensive for a complete set!







Let me know if anyone has some experience with these?

Lex

email (option): welbike@welbike.net

There are some very good racing clutches for use on Nortons, the best known being Bob Newby's.

I've known plenty of people who use them on comp bikes and they do what it says on the box.

I think the one problem that you might have is that of clearance in the pre-war primary chaincase. These clutches are primarily used open by racers with just a belt cover and seem to be based on the late AMC version of the clutch (with bonded friction back plate and cast aluminium pressure plate with adjuster).

If the NEB clutch is a dimensional replacement for the late AMC clutch then I think that you'll have difficulty getting the cover on.

I have an Atlas clutch in mine and had to take material off the rear of the back plate to gain clearance on the inner cover.

If using the AMC clutch, there is the option of using the original steel pressure plate which you can't on these six-spring replacements but as I am using McIntosh Manx matched springs and adjusters, I had to get the heads on those modified to sit lower, together with deeper cups in order to restore clearance inside the outer cover.

It's a damned tight fit in there on the old dynamo equipped bikes. The post 1958 alternator case is a bit wider.

I have a feeling in the back of my mind that some belt kits require the use of the longer Commando mainshaft. This is a straight swap in the AMC box but can't be used without extensive modification in the 'Doll's Head' or 'Laydown' boxes as they use a mainshaft thrust washer rather than pulling the shaft up tight in the inner cover.

If your clutch is problematical, I'd suggest talking with Ken McIntosh about converting the basket to bonded friction material and using later bonded friction plates. The Norton clutch is quite a sweet one when it's sorted.

I have very few problems with my M20 single spring clutch and am puzzled by the frequent references to this..It is the case that a number of aspects need to be correct for it to function well but if these are addressed at the rebuild stage it is pretty much trouble free in my experience.
A Triumph clutch is an easy substitute if one is needed and on the whole they give little trouble either. I have modified two Triumph clutches to take a bearing as in the one shown in Lex's photos...this improves them considerably, removing all the 'rocking' and 'tilting' of the clutch sprocket present in the standard unit. As well as giving better, cleaner, plate seperation this also eliminates the tendency towards the 'lost lift' that occurs as the sprocket moves backwards and forwards behind the clutch center.
In the case of the BSA the fitment of a belt kit requires the sacrifice of the crankshaft shock absorber and in the case of the Newby kit I fitted to my B33 the Jawa based clutch did not incorporate one in the clutch center. I found this lead to a noticable harshness in the transmission at 'take off'...not really an issue on a race bike but not desirable on a road machine. In any event the belt kits will not fit into the steel chaincases on an earlier BSA, only the later alloy ones.
A final option if it will fit within the case..which it probably will on an M20 as the original clutch is pretty 'deep'..is the Phil Pearson Suzuki based conversion made for the Gold Stars...this has the modern clutch but retains standard chain drive. A friend of mine had one of these fitted to a pre 65 Tribsa scrambler and its operation was both sweet and totally trouble free...Ian

email (option): ian@wright52.plus.com