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A65L oil pump woes

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Charles R:
I've dismantled and am rebuilding an A65L that had been half reassembled after the engine "blew up" in some way decades ago!  I have many items/areas to deal with to get it together again.  The passage of time has not been kind (eg, rust inside engine!) and there are non-standard parts, bent parts, missing parts, etc.  No doubt this is a common situation with a bike & parts having been in poor storage conditions for over 30 years!

Specifically I'm writing in the hope someone can shed some light on a problem with my A65L oil pump.

As the oil pump was very stiff and jammed a little at one spot I stripped it down to its bare components.  All parts were cleaned & inspected.  All parts seem to be in good condition with all the cogs meshing well and no distortion or damage to the housing etc (see photo).  However, on reassembly the rotation was still very stiff at one point.  Interestingly, removing the driving spindle (Pt No. 68-0310) and reinserting 180 to re-engage the pump reduced the stiffness.  If the driving spindle is removed, the pump can be rotated freely without any binding or stiffness.

Everything is scrupulously clean and dismantling & reassembling several times has made no difference.  Close inspection of the driving spindle appears to show that the slot is offset from centre (see photo).  Vernier measurements indicate about 0.12mm (0.005").  This could explain why the pump is running eccentrically.  Widening the slot by 0.12mm to centralise it could be the solution.

As a replacement spindle is over 40, I really don't want to buy one if it isn't really the problem!  In addition, if such a manufacturing fault could exist, I'm assuming a skim of the slot, to centre it, might be a more economic solution.

The reason I'm taking the approach of trying to mend as much as possible rather than buying replacements is that the final bill for new components looks horrendous (oil pump = 300!).

Has anyone come across such a fault, which appears to be an original manufacturing defect?

Is the approach of attempting to correct the defect in the driving spindle slot valid?

In case it helps, here are some specifics about my bike:
   registered July 1970, VOL 162 J
   frame & engine number HD 11103 A65L

Bess:
Hi Mr Ape,
                There is a SRM article on oil pumps in the October issue of Classic Bike which is worth a read.

They suggest BSA's machinery was pretty worn by the 70's so tolerances were not that great, they (I so do) I use the best from a number of secondhand parts. Even their new oil pumps are built using selective assembly to ensure the best performance.

Considering the cost you might incur building a secondhand unit, their new pump might be a better option.

Best wishes...

JulianS:
The stiffness is often experienced with oil pumps, especially the ones made from nasty zinc alloy. Bodies distort and chambers get mishapen and can pick up due to the clamping when assembled onto the crankcase and the material used.

The oil pump is the heart of the engine and has got to be spot on. If you dont want to get the SRM item, which is a first class product, then at least go for the later cast iron one which are much less prone to distortion. They are not cheap either.

Charles R:
Thanks Bess,
Interesting that build standard issues have been recognised.  I haven't got a copy of Classic Bike (I subscribe to Real Classic), so I can't see the detail of what they may be saying.
As a first stab I'm going to see if I can find a local machine shop that will ease the slot to provide a more centralised engagement.  (I could set about it with a file, but that would be pure butchery!)
Cheers, Charles

Charles R:
Hi Julian
Thanks for your response.
I've connected a simple equivalent to the driving spindle that allows me to turn it by hand.  The pump I've got seems to run beautifully smoothly when turned without the driving spindle fitted.
The thought of spending 300 on something that may be OK doesn't sit well with me, though I do appreciate the sentiments regarding that a duff pump would be a disaster!
Cheers Charles

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