oil pump oddities

Rob3912 · Post by **Rob3912** » Fri Feb 29, 2008 7:27 pm

Thanks Duncan, everything you say makes sense. If you put the two types of pump close together you can identify a slight change in the drive 'splines' from one to the other. It appears the twin start timing side end I have is wrong for the crankcase as it requires the wider pitch guide pin and pump,which does not match the drilling.

I guess this is an enthusiatic bit of mixing parts form the past. (boxes of bits!). I can try and hunt for a non existent two start pump with a narrow guide slot, or do the sensible thing and focus on common parts and engineering solutions with a drill and tap.

Good luck with the engine.

Don. yes i agree if you look from one side only its difficult to spot but by turning in all comes into focus.
Cheers again
Rob

Duncan · Post by **Duncan** » Fri Feb 29, 2008 10:00 pm

Don

Thanks, it all makes sense now.

That was until I looked at mine, the axle must be a twin start as the worm has two commencing points, the starts are not a full 180 degrees apart though more like a 160 to 170 degrees, so that means that the crank assembly must have had an earlier connecting rod fitted.

I have some work to do before I can do a trial fit in the engine case but the pump still looks suspiciously like a single start item however when I sit it on the worm it appears square, only time will tell if they are compatible.

Rob

Looks like you have a low cost solution, I may still need to embark on the hunt though.

itma · Post by **itma** » Fri Feb 29, 2008 10:52 pm

the axle should be marked 2s same as the pump.
the pump is marked at the rear end
the axle is marked 2s on the threaded end.
This latter is often difficult to see, and often only partially present.
It is possible to build an engine with mixed parts, it will not run for long.
Any attempt to run non compatible parts here will result in a lot of tears as you empty your wallet once again.
Don't stint.
Personally I would find another set of crankcases, or even a half set.
penny wise pound foolish.

Rob3912 · Post by **Rob3912** » Fri Feb 29, 2008 10:57 pm

Duncan have you tried lightly oiling and assembling the crank in the timing side and fitting the pump in with the guide pin. With the gentlest of pressures turn the assembly. if its wrong it will lock out, do not force it or damage to valuable parts will occur. This is a simple test of compatability, or non-compatability as the case may be.

Been into Bacon and viewed the pumps,from the two I have I would judge the far left to be single start 3/16 guide (straighter splines). the one centre to be 2 start 3/16 guide(angled splines) whils the one on the right is two start 1/4 guide(angled splines) Bacon appears spot on with his study and states the centre one as being the 47 only. Its obviously a hens tooth item as its one year only but does suggest your two start crankpin is correct, as is mine. Which is something worth note.

I feel all is becoming clear now and an incomplete 47 engine is problematical for spares!

Best wishes Rob

Rob3912 · Post by **Rob3912** » Fri Feb 29, 2008 11:03 pm

Itma. Thanks to Ebay I have done just that although I no longer have the valve lifter at the base. Its an alternative to modyfying a perfectly good part.

Nothing is straightforward. An ally head will suffice as i have the short conrod and barrel combination. Dont you just love Bitsa's.

Do you predict this will be problematic.

Rob

Biscuit · Post by **Biscuit** » Fri Feb 29, 2008 11:22 pm

How can you possibly have a two-start worm/thread where the starts of the threads are not at 180 deg.?. Having cut many of these in my lifetime, I look forward to an answer with interest.

Duncan · Post by **Duncan** » Sat Mar 01, 2008 11:10 pm

Ken

Thanks for the warning, as you state it would be foolish to try and match incompatible parts, what I was alluding to is that this bike is not the main focus of my workshop time at the moment so it will be a while before I get around to establishing what assortment of parts I have. Problem is I can not stop thinking about it now so I have placed some pictures on the net for further comment.

http://picasaweb.google.co.uk/Hampshire ... ilPumpWorm

No sign of a 2S on either the pump or axle. I am now almost fully convinced that the pump is a pre 47 item.

Rob

When I get the time I will clean, prepare and assemble the parts, I may also have a lead for some hens teeth, watch this space.

Alan

As you state I was expecting the thread to start at 180 degrees apart, which was why I mentioned it. Looking more closely I believe that the factory must have ground the start of the thread away, possibly to clear an oil way.

http://picasaweb.google.co.uk/Hampshire ... 3819562114

Edited by - Duncan on 01 Mar 2008 11:11:12 PM

Biscuit · Post by **Biscuit** » Sat Mar 01, 2008 11:44 pm

I'm sure that must be the answer Duncan. After I posted the comment I did feel a little uncomfortable with, seemed a little facetious.

Rob3912 · Post by **Rob3912** » Sun Mar 02, 2008 8:32 pm

Duncan. i have viewed your pictures, it looks like a single start item to me too after comparing the ones I have and can match to crankshaft worms. Obviously Mr Bacon did his homework well but would have made life simpler for us all if he had noted the guide pin arrangements too.

I have been thinking about why the change in the guide pin design. i can only think that the extra load from a two start pump was too great for the 3/16 pin and an increase was necessary to prevent failure.

Does any member know if this was the case, if so it makes sense to go up a size, even a purist would forgive us for that. I hope.

Best wishes
Rob

Duncan · Post by **Duncan** » Mon Mar 03, 2008 9:39 pm

Rob

If you want reuse your crank cases and need a new, 47 only, twin start oil pump then you need to talk to Andrew Engineering who have a number in stock.

The prospect of the pin shearing will however always be on my mind, thanks for adding that to my burden of worries.