Removing oil pump A50

[B-S-Africa]

Hi,

I am in the process of removing the oil pump. I have what I think is an above and beyond normal or acceptable wet sumping. I want to inspect / clean / replace the ball and spring and also clean out the oil pump. This is a 1970 model that has currently 7400km on the clock of which I personally had put on about a 1000km. Why I mention this, is that the bike (and engine) still has very little wear and tear. It had stood for about 45 years indoors. I removed the inner cover and exposed the oil pump. How do I lock the engine? I flattened the tab-washer under the crankshaft nut. I turned the nut clockwise (left hand thread). I expected the engine to turn as well. Next I put the bike in first gear and had the wife standing on the rear brake (this works with my other bikes). Yet the engine kept turning.

Can I lock the shaft on the right side by the rotor? Or is there some other technique? 

[AdrianS]

You don't need to lock the engine to remove the oil pump.
3 screws/bolts hold it onto the engine. Remove these (they are not tight) and pull the pump off.
The gear on the crank is to drive the pump and doesn't have to be removed.
To lock the engine, the best way is to put a bar through the Conrod small ends and rest this against the crankcase on some wood but you need to take off the head, barrel and pistons. Failing that an impact gun can be used. If I remember the nut holding the oil pump drive on may be a left hand thread.

[B-S-Africa]

Erratum  to my first post  - The rotor is left. Not right.

Thank you for your speedy reply. What you wrote, was what I initially did. NO WAY the pump comes off. I, very carefully, wedge a screwdriver between the casing and the pump and got the pump to wiggle a bit. I stopped that exercise once I felt I may start to use excessive force. So the pump "wiggles" slightly at this stage.  Then I went the tried and tested way, that of reading the manual when all else fails. Three of my manuals prescribe the process I explained above (that of removing the worm gear).

Now question is: HOW do I get the pump away from the casing. All three nuts and spring washes are removed.

[DAVE BRADY]

Hi,

If still standard the pump is held on studs.  Ideally the drive worm should be unscrewed as the pump is eased off the studs.  If the pump turns easily then you may be able to ease it off without undoing the drive worm.  With such a low mileage it is unlikely that the pump is worn much so a good clean will probably be enough.  Once the pump is off, the ball and spring can be inspected but they are so cheap it is just as well to replace them.  On refitting, get good gasket and do not over tighten the nuts - it is only a 8 to 10 ft/lbs of torque.  There is a section in the owners manual about the servicing the pump.

Dave.

ps.  To undo the worm drive and its locknut you may be able to shock it loose.  With good fitting socket held firmly on and the engine against compression, a sharp whack on the tommy bar should move it.

[B-S-Africa]

I attach two pictures, one before removal of the three nuts and one with pump slightly loose. I pulled and jerked at it again. Stuck, except for that wee wiggle.

Hi Dave, I had good fitting socket firmly on, engine in first gear, rear brake fully down and a proper tommy bar. It only turned the engine. That was clockwise (left hand thread).

Thinking out loud: what if I take the pump apart in situ? Then remove the housing of the pump? Then access the ball and spring? Or apply more pressure in wedging the pump off?

[ChrisG]

Its been a while since I removed one that was held by studs but from memory, I removed the worm wheel nuts and turned the crank as I tugged at the pump. I cant remember which way to turn the crank but you will soon find out.

Hope that helps

Chris

[Mike Farmer]

 

To remove that nut I would suggest an impact driver and a properly fitting socket. Then in gear etc. It should only need one good whack.

One point comes to mind and that may consider. If the nuts have been over tightend such action could well have had a crushing effect on the alluminium pump casing around the stud, causing a pinch action on the stud thread.

You may have to consider using two nuts(locked) and taking the studs out.

MIke

[B-S-Africa]

One point comes to mind and that may consider. If the nuts have been over tightend such action could well have had a crushing effect on the alluminium pump casing around the stud, causing a pinch action on the stud thread.

You may have to consider using two nuts(locked) and taking the studs out.

MIke

I started to have a similar thought. I used a spot light and examined the whole of the pump as it sits there, while wiggling it, to see if I can't see the why it is stuck. And the why is still visually hidden from me. The pump turns very nicely when I turn the centre nut. It turns both ways very smoothly.

Thanks

[DAVE BRADY]

Hi,

I have just removed and refitted an A65 pump with studs. Try a sharp whack on the tommy bar with the engine against compression and if needed in gear with the rear brake on. Just the whack on the tommy bar worked for me. The problem with not undoing the worm drive at the same time is that the pump will snag on the hex. part.  Also, undoing the worm drive will help to ease the pump off evenly.
As Mike said the pump body could be distorted but I guess that the low mileage suggests that this pump was fitted at the factory and would not have been over tightened.
When refitting, the worm drive can be put on afterwards as the worm goes to the inner end and can be wound on.  It will turn the pump as it does this.
I would not recommend using any force to get the pump off as the oil ways are quite close to the edge and could be damaged so gentle easing only.

Dave.

ps  Take the inspection cover off the primary case and use a socket on the rotor nut.  If you can hold this and undo the worm drive nut against this.   

[AdrianS]

I recently stripped my A50 for a complete rebuild. Oil pump came off by just undoing the 3 bolts. It was an SRM pump - don't know if these fit differently to the standard pump but came off very easily.

[DAVE BRADY]

Hi Adrian,

I believe that the standard arrangement is studs but some owners have switched to Allen type screws to make it easier to remove and refit the pump.  The SRM kit comes with new screws to replace the studs and make it easier to fit the new pump.

Dave.

[B-S-Africa]

And it is OFF!

I have planning this little exercise for a while now. Prepped myself mentally as well. Had everything ready for 09h00 this morning. Made a strong pot of coffee, stuffed a good pipe and 09h00 I pushed the bike into the workshop. Had a cold one in the fridge for afterwards, which was estimated for 13h00. Midday came and went. It is now dark and night. And I am back with coffee. Tomorrow is another day. Calling it a day (or night).

I did the first gear, wify on brakes, socket and tommy bar thing again. The engine puts up virtually no resistance. So off with the primary cover, spanner on the nut for the rotor and off the other nut came. The worm gear also. Then the pump.

Thanks gents for all your valuable inputs!