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Discussion Starter #1
I've read a few posts going back to 2014 but haven't found exactly what I need. If I've missed it please point me in the right direction.
I looked at taper-roller head bearings for the above bike but was advised that it wasn't really worth it - as has been said on this forum - so have just replaced the originals with new ball bearings. The races are proud of the head lug casting by about 1/16", which is how I recall the originals sat and they certainly feel like they're fully home; right so far?
The (original) stem nut is tubular, has a split along its entire length and has a shoulder that will push the top yoke down on to the bearing dust cover. My very pretty yokes are just back from stoving but they have painted inside where the stem nut and stanchions should pass. The stem nut does not now fit (I haven't tried the stanchions). I had not thought the paint thickness would make so much difference. Do I correctly deduce that all these holes should be bare metal?
Should I lubricate the stanchions, etc., before assembly in the yokes and grease or otherwise protect them after (and with what)? These stanchions are not chromed so although the nacelle shrouds will afford some protection, the bare metal of the old ones was beautifully pitted and I don't want that again.
 

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Hi,

Firstly, welcome to CVV. :)

Uh-uh, fraid not, that's for the pre-unit 500 (and 650). T100A is '57-on unit C-range, pre-'63 covered by (Triumph) INSTRUCTION MANUAL No.4 (available to buy online but not read online :().

looked at taper-roller head bearings for the above bike but was advised that it wasn't really worth it
... and afaik not possible ... Pre-'67 C-range have smaller frame steering head, bearings and steering stem than the 'B-range' (pre-unit 500 and 650 twins, unit 650 and 750 twins), for which the usual replacement or oe taper-roller bearings are available.

(original) stem nut is tubular, has a split along its entire length and has a shoulder that will push the top yoke down on to the bearing dust cover.
Uh-uh ...

Although the steering bearing aren't taper-rollers, certainly where the balls run on the races on the steering stem is coned (the bearing type is "cup-and-cone").

The relevant steering parts are:-

. frame steering head casting, into which top and bottom bearing "cups" are an interference-fit in the ID, up to a slightly-smaller ID, making a "stop" or "land" for each cup;

. lower yoke with steering stem, the lower bearing "cone" sits around the stem and on the bottom yoke;

. between each "cup and "cone" are half the parts book's listed 48 balls (you'll have tediously stuck these to the bottom cone and the top cup with grease?);

. in addition to the bottom bearing cone, the steering stem also protrudes through the bottom cup, the frame steering head casting, the top cup and the top cone, the latter incorporating the dust cover.

The steering stem nut should pass through the top yoke and bear on the top cone/dust cover. When the nut's turned clockwise, because it bears on top cone, balls and cup and they're prevented from moving downwards into the frame steering head because the cup is (should be) on its aforementioned smaller-ID stop/land, the nut will pull the steering stem upwards. In turn, the steering stem will pull up the bottom yoke, bearing cone and balls; similar to the top cup, the bottom bearing parts can't (shouldn't) move up into the frame steering head because the bottom cup also is (should be) on its smaller-ID stop/land. So continuing to turn the steering stem nut simply squeezes the clearances from between the bearing components 'til the steering is immovable.

The top yoke should simply sit on the top bearing cone/dust cover. The split tubular part of the steering stem nut under the hex.should be longer than the thickness of the top yoke casting, so I would expect a small space between the top surface of the yoke and the underside of the stem nut hex.

Once the steering's adjusted by the nut on the steering stem, the top yoke should simply be clamped around the nut to prevent the nut moving and consequently altering the pressure on the steering bearings.

The races are proud of the head lug casting by about 1/16",
Hmmm ... given the top cone incorporates the dust cover, is the latter positioned to prevent dust entering the bearing?

yokes are just back from stoving
have painted inside where the stem nut and stanchions should pass. The stem nut does not now fit (I haven't tried the stanchions). I had not thought the paint thickness would make so much difference.
The yokes, stanchions and steering stem nut are only separated by a few thousandths of inch. Decent stove enamelling is pretty thick.

all these holes should be bare metal?
Essentially yes, although the top yoke steering stem nut hole could have a layer of enamel as long as there's clearance for the nut.

stanchions are not chromed
Should I lubricate the stanchions, etc., before assembly in the yokes and grease or otherwise protect them after
Absolutely.

I'd certainly grease the bare metal of both yokes and stanchions, or moisture will definitely rust them together. :(

nacelle shrouds will afford some protection,
The only protection the shrouds afford is to owners' sensibilities, so you don't see the stanchions' bare metal rusting ... 😣 Fwiw, I cover bare metal with either grease or beeswax furniture polish.

Fwiw, I use paint stripper intended for furniture restoration to remove powder-coating - the stripper's liquid enough to be applied with a paint brush but thick enough to adhere to surfaces at any angle, it's relatively mild and water-soluble.

Hth.

Regards,
 

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Discussion Starter #4
Dave; like a custom flap wheel, effectively; thanks. Also for the link but, as StuartMac said, not for mine, I'm afraid. FYI, this site has a number of parts books, service bulletins, etc., that can be read on line.

StuartMac; I explained poorly. The top cone is integral with the dust cover, as you say, and the stem nut is currently holding the assembly together, while I clean the hole in the top yoke. It's all as you describe and, having held the top yoke up to compare, you are right that there will be about 40 thou gap under the shoulder of the stem nut (can't use metric measures on this forum). Just as well you pointed it out, or I'd have worried about the gap. :mad:
I can confirm that the dust cover fits nicely over the head lug casting. The steering rotates, lock to lock, very smoothly. No separate lock stops on this model so I have to be careful not to chip the new paint. You are right about thickness of paint; it's impeding fitting some screws as well.
 

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Hi,

No separate lock stops on this model
There were and are, the C-range parts books tell porkies:-

. In the first ('58 and '59), the nacelle forks illustration is exactly the same as the one in the pre-units' books, including the pre-unit's lower yoke fork casting with cast lock stops.

. Nevertheless, the part numbers aren't the same - H1112 for C-range, H1229 for pre-unit. If you look these up on Google or similar with the part number in the '73-on format (i.e. "triumph 97-1112" and "triumph 97-1229"), the returned images show the C-range bottom yoke never had the pre-units' bottom yoke's cast lock stops ... :rolleyes:

. In any '60-'66 C-range parts book, H1112 is correctly illustrated without cast fork stops; however, what the draughtsman failed to change at the same time was the nuts securing the lower yoke stanchion pinch and nacelle mounting bolts - part no. 6, these remained the pre-units' E2412 plain nuts according to the parts books. :(

. In real life, "No separate lock stops" doesn't make any sense at all; even when these bikes were new, no developed country's government department responsible for vehicle safety would permit a motorcycle that could trap a rider's hands between handlebars and fuel tank in use or in an accident.

. So the C-range always had lock stops. But, for some bizarre reason, Meriden never illustrated nor listed them on the parts books' nacelle forks pages ... only on the same parts books' non-nacelle forks pages ... 😣 ... part no. 6, the nuts with an extension rod, that fasten to the aforementioned lower yoke stanchion pinch (and nacelle mounting) bolts.

Educated guess says your bike has the (larger) 3-1/2-US-gallon (nominal) tank so you want H1335 with the longer extension rod ... (y)

Hth.

Regards,
 

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Discussion Starter #6
Very disappointing. I already knew my Haynes was full of holes, as far as my early, 1961 model was concerned, so I had been using the parts book more and more. What to do if I can't trust the words from the horse's mouth, either?
As for hand-trapping, I had thought I would find, when the bike was together, that there was in fact some mechanism that provided a 'stop' (ie cast-in; the operative part of my post being "...separate lock stops...") and that I just hadn't yet noted it. Furthermore, I believe the standard 'bars are raised above the tank thus no trapping point should exist. As it is, the bike is not together and has not been for years, so neither point was currently evident to me, nor clear in my memory. [and let us draw a veil over the fact that the previous owner had fitted clip-ons halfway between the yokes - keeping the standard tank - without any apparent precaution in this respect: what fun!].
I shall look out for a pair of H1335; thanks for the tip. btw, they're on pages 46/47 of the Parts Catalogue #4.

I have to say, I'm really enjoying this forum. (y)
 
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