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Messages - Charles R

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Twins / A65L oil pump woes
« on: 24 October, 2017, 13:28:57 »
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

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