Author Topic: C11, 12 oil pumps  (Read 426 times)

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Offline parkes

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C11, 12 oil pumps
« on: March 10, 2019, 10:35:35 pm »
I have read stuff including opinions on this forum regarding refurb of the oil pump. Firstly the pump is very effective and not rubbish as suggested, originally made to a high degree of accuracy and  is well capable of delivering very high pressure indeed. It's the same pump as fitted to the Gold star engine.
If you do feel the need to attempt a refurb, do not remove material from the body faces with "a bit of a rub on abrasive paper" and be warned, they don't correctly assemble easily.
How do I know? I both machined them and tested them throughout the sixties. Incidentally, various tests were applied to every pump, supply flow rate, return flow rate and supply pressure, restricting the supply would generated huge pressure such that the worm drive on the test rig would literally burn out in seconds.

Offline donkey

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Re: C11, 12 oil pumps
« Reply #1 on: March 11, 2019, 03:16:04 am »
 :) I like, more please
donkey

Offline timsdad

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Re: C11, 12 oil pumps
« Reply #2 on: March 11, 2019, 07:22:12 am »
They could do with you at Draganfly's, Mr p, - I had to sort through their box full before I found a re-built one I was happy with!


Ray
Just a motorcyclist.

Offline parkes

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Re: C11, 12 oil pumps
« Reply #3 on: March 27, 2019, 09:43:02 pm »
As I said, "not easy to assemble correctly" the drive side plate needed tapped with a mallet to get everything lined up so as to get it free enough to be rotated with light finger pressure. Knowing where to tap it and how hard to tap it.....aint easy but every pump had to be set like that even the big twin pumps.
The chances of a well meaning restorer getting it right without resistance to rotate or tightness I'd say was remote.
The first section I worked on as a 16 year old BSA apprentice straight from school was the pump section, machining the parts, assembling and testing. £3-7-6d a week and the best of days.

Offline Donald

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Re: C11, 12 oil pumps
« Reply #4 on: March 27, 2019, 10:47:43 pm »
Hi there, so can you enlighten us "well meaning restorers" as to the best way to getting a seized pump operational again?

Offline parkes

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Re: C11, 12 oil pumps
« Reply #5 on: March 27, 2019, 11:35:14 pm »
And Hi to you too, I'm also a well meaning restorer by the way, no offence intended I was merely pointing out that what might seemingly be a simple task can turn out to be anything but.
I suppose the answer to the question is, it depends on how the pump became seized? was it as a consequence of a rebuild or did it fail in service. I don't have definite answers of course, only opinions but if it failed in service I'd suspect contamination of some sort. Otherwise at worst I'd say it's a case of misalignment hence the need for tapping back into position of the plate through which the drive spindle exits. A thou or two is all it takes to lock things up so it's binding rather than seized. The body and end plate material is Mazak, it's a superb bearing material but relatively soft and can easily be damaged to the point of distortion if abused. I think it extremely unwise to remove even the slightest amount of material from the faces of the main body as this will reduce the pockets in which the gears sit preventing them from rotating when assembled, the chances of recovering such a situation are nil. This may not be of any help but I'm happy to discuss further.
PS, if you need to go the "tapping" route don't over tighten the two screws holding the assembly together.

Offline Ginge

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Re: C11, 12 oil pumps
« Reply #6 on: March 27, 2019, 11:47:00 pm »
Parkes,

That’s good info.

Is there any harm in lapping the gears together with a mild abrasive like grinding paste or toothpaste?  Sometimes one pump is built up out of a couple of old pumps and the gears don’t quite mesh perfectly.
Ginge.

Offline Donald

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Re: C11, 12 oil pumps
« Reply #7 on: March 27, 2019, 11:53:04 pm »
Hi there, no offence taken or meant, most of us find the pumps have been lying about in box of bits or in an engine that's been stored for years in someone's damp shed. Usually they are seized solid and one has no option but to strip and clean. I was just wondering how you would recommend going about that.

Offline parkes

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Re: C11, 12 oil pumps
« Reply #8 on: March 28, 2019, 03:56:19 pm »
Lapping gears whilst still in the pump body will only wear the body so not a good idea, the gears are hardened and lapping wouldn't achieve anything of value. these pumps were never selectively assembled, all the parts came out of the same box so to speak. Obviously the gears were produced with acceptable manufacturing tolerances which resulted in some pumps having a slightly better performance, these were earmarked for Goldstar engines otherwise all the parts were the same, there should be no need to go looking for gears that fit better than others. However there was a tooth profile change somewhere along the line but you can easily see the difference, don't try mixing them up. Another change involved increasing the width of gears to enhance flow rate.
The pump body is an aluminium/zinc alloy and will surface oxidise over time which doesn't look particularly attractive but I doubt will affect performance unless gone so far as to start growing barnacles as can happen to aluminium. I would suspect a pump in this condition to be past recovery.
If gears rotate freely in the body, all should be well, if the drive spindle is a bit tight in the end plate; a bit of Scotch Brite on the dowel should remove any film of oxide.
It should be noted that I'm no expert, just an old flatulent who messes about with bikes according to "senior management".

Offline Donald

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Re: C11, 12 oil pumps
« Reply #9 on: March 28, 2019, 04:51:57 pm »
Hi there Parkes, there are plenty of old flatulents on this board , just like me, LOL.
The biggest challenge is to get the crud out of the gear cavity's and the face plates cleaned up, I personally used T cut and an battery drill to spin it up, washed in petrol, and then reassemble then spin in oil, Is there a torque setting for the bolts

Offline parkes

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Re: C11, 12 oil pumps
« Reply #10 on: March 28, 2019, 05:15:40 pm »
Hi Donald, it's Dave this end by the way. (A good old un will beat a good young un any day).
Torque setting were a bit posh back in the day, the only torque wrench I ever saw used at BSA was for cylinder head fixings. As for the pump, as long as you don't go far enough to strip the thread.
Personally I avoid that silicon rubber sealing 'stuff'......risk of bunging oil ways up, red Hermetite for me. Originally the pumps and all the engine casings were sealed on assembly with shellac thinned out with meths, a sort of brown varnish..........probably why BSA's always seemed to leak a bit. Fast approaching a similar condition 'meself.
Your pump body recovery method sounds good to me, try not to increase the diameter of the pocket in which the gears sit, a critical feature of the pumping action.

Offline stev60

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Re: C11, 12 oil pumps
« Reply #11 on: March 28, 2019, 06:34:18 pm »
 recently had a C11 motor apart and found oil pump tight and when bolts were tightened to an acceptable tightness would not turn, so had been running for however long with slightly loose bolts. plate and body were in good shape. In the end I machined a few thou off each gear. The pump works perfectly with bolts tight and the return is actually better than previous, so what had happened to pump in previous life is only a guess, could have been assembled from a box of parts. Just sort of goes with a lot of other stuff I found done in the past , like who would recondition a motor and not clean out the oil tank and the filter wasnt even there ::) 

Offline parkes

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Re: C11, 12 oil pumps
« Reply #12 on: March 28, 2019, 07:50:58 pm »
You never quite know what's in store when you buy an old bike that's for sure. I've found metric wheel bearings made to fit imperial housings by angle grinding the outer race and insulation tape around the wheel spindle to make it fit the bearing bore, epoxy resin in tapped holes to secure a wrong size screw, stripped threads made good with cardboard around the screw thread.................it takes all sorts.
I'm totally amazed that you not only "machined" material off pump gears (you must have some pretty good kit to be able to do that) but you claim the pump worked better, originally the gears and their housing were toleranced to within half a thou in order to achieve  good pressure both feed and return.............I'm amazed.

Online Tman

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Re: C11, 12 oil pumps
« Reply #13 on: March 28, 2019, 08:24:42 pm »
The idea of putting a mild abrasive through the pump is a good one; Velocette recommended it for their geared pumps using some weird stuff like "Red Turkey Powder" or somesuch daft trade name. I spun it in a pillar drill using a mix of engine oil and a fine grade lapping paste. Took a while but it worked, and the pump gives a good steady jet of scavenged oil.
It's sh*t or bust really, as a stiff pump is too liable to strip it's gears.

Offline parkes

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Re: C11, 12 oil pumps
« Reply #14 on: March 28, 2019, 09:38:59 pm »
I'd be concerned that abrasive particles might become embedded in the soft pump body material although I can see how it would free up stiff gubgins. As for the BSA oil pump, I've recovered many non rotating pumps without  putting abrasive material inside them just by assembling the correctly.