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Topics - MALCOLM.JOHNSON

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Twins / Torque settings again.
« on: 11 November, 2017, 14:15:12 »
I have recently rebuilt the 1952 A7 engine and tightened the big end caps on the alloy connecting rods using data from the BSA SERVICE SHEET No.208. My rods use the later 26 t.p.i. bolts and the  recommended torque setting for those in the service sheet is 8.5 lbs.ft. Sometime afterwards I was reading the D. W. Munro book on BSA Twins and in this he quotes 22lbs.ft. for all the models. I borrowed a very hi tech torque wrench for the job as my own was off the scale at such a low setting. I am having sleepless nights about using the lower figure - any words of comfort out there.

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Twins / Plunger A7 clutch
« on: 28 May, 2017, 21:44:22 »
On rebuilding my 1952 A7 clutch, I notice that if I put a straight edge across the friction surface of the outer pressure plate (67-3245), there is a pronounced "dish" ie it is not flat. The "dishing" is uniform across all diameters.  The difference is about 1mm at the inner diameter of the friction surface. I would not expect this, but on looking at a spare clutch that I have, it is exactly the same? Both correct or both wrong? All other plates are dead flat. Don`t want to buy new if that is how they are.

The outer plate is made up of a pressed spring plate, spot welded to what looks like a standard plain driven plate. Does the spot welding create this "dishing"? How/why would it need to be dished. Could easily be overlooked.

Whilst on the subject I am contemplating using "Surflex type friction plates, which in many applications are wet with oil, but not so in this type of BSA clutch if properly sealed. Do we still use the cover?   Appreciate informed thoughts on this.  Thanks.

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The Star and Garter / TYRE SIZES/PRESSURES FRONT AND REAR
« on: 27 March, 2017, 21:29:02 »
Been having discussions/arguments recently regarding tyre fitments and pressures used on typical post war motorcycles and would welcome opinions from the forum. What is the point in having different tyres front and rear? A typical post war machine with 19 inch WM2 rims may often specify 3.00 front and say 3.50 rear. Why not have them both the same? Early A7 with Q/D hubs front and rear were intended to be interchanged. I can see that modern sports bikes need them different, but our relatively low powered classics - I am not so sure. Also early specification for tyre pressures, to me seem on the low side for modern tyre equivalents. Love to hear your views.

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Twins / SMITHS CHRONOMETRIC SPEEDOMETER - LUBRICATION.
« on: 19 February, 2017, 20:28:08 »
I have removed the bezel, glass and instrument mechanism, to allow me to do a proper job of re-painting the case, cleaning glass etc. I have no intention of any further dismantling as the speedometer seems to work fine, despite no motion over many years standing unused. Have members any thoughts about taking the opportunity of lubricating the mechanism while it is possible to do so? I had wondered about a light spray with WD40 allowing time to drain off before reassembly back into the case.

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