Author Topic: A65L oil pump woes  (Read 255 times)

0 Members and 1 Guest are viewing this topic.

Charles R

  • Star
  • *
  • Posts: 16
    • View Profile
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

Bess

  • Silver Star
  • ****
  • Posts: 251
    • View Profile
Re: A65L oil pump woes
« Reply #1 on: 24 October, 2017, 15:19:58 »
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

  • Empire Star
  • *****
  • Posts: 549
  • A10
    • View Profile
Re: A65L oil pump woes
« Reply #2 on: 24 October, 2017, 15:58:40 »
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.
« Last Edit: 24 October, 2017, 16:01:19 by JulianS »

Charles R

  • Star
  • *
  • Posts: 16
    • View Profile
Re: A65L oil pump woes
« Reply #3 on: 24 October, 2017, 15:59:54 »
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

  • Star
  • *
  • Posts: 16
    • View Profile
Re: A65L oil pump woes
« Reply #4 on: 24 October, 2017, 16:06:06 »
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

Mike Farmer

  • Royal Star
  • ***
  • Posts: 215
    • View Profile
Re: A65L oil pump woes
« Reply #5 on: 25 October, 2017, 10:05:14 »
 :)

This may sound a bit radical, but you might try just a very very small amount of extra fine grinding paste, but for an absolute minimum amount of rotations.

Mike 8)

Charles R

  • Star
  • *
  • Posts: 16
    • View Profile
Re: A65L oil pump woes
« Reply #6 on: 25 October, 2017, 10:48:53 »
Mike
Hadn't dared to consider anything like that!  But, it's a thought!
Not sure how to get enough pressure on the grinding paste onto the inside surface of the groove to remove up to 0.005" off that face.  I had considered a needle file - the steel is quite hard, so it will need a lot of pressure applied.  (Haven't tried it yet as I've temporarily misplaced my needle files!)
Another method might be to temporarily fit the driving spindle with some grinding paste on the relevant face of the slot and then rotate it with a drill to see if it grinds that face.  As the driving spindle is isolated by an O ring from where the pump gears are, I suppose there should be little danger of the grinding paste getting into the pump itself.  If it works, I can strip the pump down again (I'm getting very slick at doing it!) and clean everything really well before reassembly.
I suspect it may be difficult to remove enough material with the grinding paste to make a significant difference - but it may be worth a try.
Cheers, Charles

JulianS

  • Empire Star
  • *****
  • Posts: 549
  • A10
    • View Profile
Re: A65L oil pump woes
« Reply #7 on: 25 October, 2017, 16:54:29 »
Beware grinding paste sticking in the soft zinc alloy.

With the drive being off centre then it will be forcing the toothed wheel into the side of the oil chambers  causing uneven wear.

You can grind away the high spots but you cannot fill in the low spots.

Do you know what caused the original blowup?

Charles R

  • Star
  • *
  • Posts: 16
    • View Profile
Re: A65L oil pump woes
« Reply #8 on: 25 October, 2017, 18:45:14 »
Dear All
Thank you for your help on this matter.
Regarding the engine failure, I only got the info third hand, as the person who sold me the bike (I knew him through work & it was an absolute bargain) said he was helping out someone who wished to get it out of their shed!  I was simply told that the engine had seized and that it had been re-bored etc.  So it could have been poor oil pressure!!
I've spent this afternoon in my shed looking at it, scratching my head and all else that happens in a shed before actual work commences.  The penny dropped - how about a Dremmel?  Well, that's exactly what I've done using a grinding disc that just fitted in the slot.  The slot has been eased by, perhaps, 0.002" to 0.003" and, hey presto, no more binding.
The pump has been completely dismantled, thoroughly cleaned and put back together again with a good dose of 3-in-1.
It runs completely smoothly and spins up perfectly when driven by an electric drill.
Thanks again for helping me think through this matter.
Cheers Charles

Bess

  • Silver Star
  • ****
  • Posts: 251
    • View Profile
Re: A65L oil pump woes
« Reply #9 on: 25 October, 2017, 19:02:20 »
 :)