Fitting a new steering stem

mdt-son

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Hi all.
I have obtained a NOS 1970 interim top yoke, p/n 06-1915, which has a rusty solid stem, unlike 1972 yokes . I want to replace the stem against the 1972 type hollow stem.
Stem diameter is identical, and I hope that goes for the knurled section as well. Has anyone completed a similar swap?
Will a new stem (AN part no. 06-1918) provide necessary grip, or will the yoke require an oversize stem in the interference area?

The old stem will be carefully removed by cutting it below the yoke and by machining a 24.5mm co-centric bore. The remaining "sleeve" will be removed by carefully making a diametral cut with a hacksaw.
There may be other ways ...

- Knut
 
The early models have the stem attached to the lower yoke. The later type are connected to the upper yoke. I don’t recall my ‘70 having a “solid” stem.
 
The early models have the stem attached to the lower yoke. The later type are connected to the upper yoke. I don’t recall my ‘70 having a “solid” stem.

That's right. 1968-1970 models used the triple tree inherited from the Atlas & G15 models. The stem is anchored at the lower yoke and is a tube.
The change-over from the Atlas-style triple tree took place as part of the front end face-lift for 1971 (Sept. 1970). As far as i know, Commando R, S and Roadster Mk1 models all used the Atlas-styled triple tree.

I can assure you this stem is solid and therefore quite heavy (06-1915 indicates the drawing was made during the 1970 model year). Spare part number of the rubber plug is 06-2305, which indicates it was drawn during the 1971 model year, to be fitted for the 1972 model year, possibly in connection with introduction of the Combat model (January 1972). Introduction of the hollow stem may have been a weight-saving exercise.

- Knut
 
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I have obtained a NOS 1970 interim top yoke, p/n 06-1915, which has a rusty solid stem, unlike 1972 yokes .

I can assure you this stem is solid, and quite heavy (06-1915 indicates the drawing was made during the 1970 model year). Spare part number of the rubber plug is 06-2305, which indicates it was drawn during the 1971 model year, to be fitted for the 1972 model year, possibly in connection with introduction of the Combat model (January 1972).


Although the "Interim" parts list is described by AN as "1970" it is little different to "1971".

The 750 upper yoke with stem I believe was introduced from serial 141783 (Jan '71) and was part 06-1915 from the Interim list through to '73.
The 06-2305 is in the Interim...
Fitting a new steering stem

...and "1971" parts list.
 
Although the "Interim" parts list is described by AN as "1970" it is little different to "1971".

The 750 upper yoke with stem I believe was introduced from serial 141783 (Jan '71) and was part 06-1915 from the Interim list through to '73.
The 06-2305 is in the Interim...
Yes LAB, I stand corrected. S/N 141783 appears to mark the introduction of the new style fork yokes. They were developed during Q1-Q2 of 1970 while the rubber plug seems to be an afterthought, apparently hastily developed from September to December of 1970.
I wonder if I've got a pre-production yoke. maybe a demo model for the US Sales organization? It's evidently a NOS item, sourced from Bob Raber's ex strock. As mentioned, the stem is a solid bar, but threaded at the lower end in the usual way.

- Knut
 
I would have the solid stem bored out to a stock wall thickness, significantly reducing the weight.
Line boring a rusty stem, with all the challenges of positioning and clamping the yoke? Nahh, that will be much too expensive, and I don't know if bearing seats are salvageable. Fitting a new stem (possibly of a better alloy) will be cheaper.

- Knut
 
Does any of you know the appropriate lock (snap) ring to be used for the steering stem 06-1918? Grove diameter is d = 0.9395" (approx. 15/16") and with is 0.0635" square. NA does not list the lock ring by part number.

Peterson Spring (OH, USA) list one (0.91" x 0.049") which should fit perfectly. Metric snap rings from Cirteq and similar manufactureres don't fit as well.

Anyone know of a retail seller (in the UK preferably) who sells imperial size lock rings? I doubt AN is willing to offer me any.

- Knut
 

061918C CIRCLIP - YOKE STEM - FROM 141783 ONWARDS

?
"CIRCLIP WHICH IS FITTED TO THE STEM USED IN THE RGM ALLOY FORK YOKES. (PART NUMBER 061918AY).

OUTSIDE DIAMETER: 25.5MM
INSIDE DIAMETER: 22MM
"
 
Thank you so much for replying, Les.

I looked up DN0257. It is for the rotary F1, unlikely to fit the Commando, but I will inquire.
It's unlikely the RGM circlip will fit, otherwise they would have advertised the commonality of parts.

I am putting my bet on Norvil's circlip, which looks promising. Thank you for the referral!
(I hadn't noticed they have a "yokes" parts section!)

- Knut
 
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Les, I think this could be the part I am looking for. The other 07.xxxxx part number listed is a weld-on part for the Mk3 frame. I will ask Tech Support tomorrow. Strangely they didn't mention it in their message today.

Edit next day: A strange message arrived from Tech Support, in which they linked to the shop detail (07.00096). I guess it's an admittal, "we forgot, but this is it". All right, nobody is perfect. At least they carry the part.

- Knut
 
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The other 07.xxxxx part number listed is a weld-on part for the Mk3 frame.

The steering stop lug 07.00180 would be for '1971' and later frames, not just Mk3.
 
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