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[simon]

Those who read my last post will be aware that I recently upgraded my oil pump to the high capacity version as well as replacing the drive spindle using the more expensive English version. A month down the track the bike develops a very nasty bottom end knock so I pull it apart to find that the new spindle has completely shit itself. I immediately contacted our hosts to ask them what they would do about a faulty part. Before they get back to me (they are no doubt groaning with excess Turkey and Ham somewhere at the moment) I swatted up assuming that the oil pressure relief valve has failed. Not so I discover there isn't one. Weirdly the bike doesn't have the lovely little sprung ball in the crank that my old 51 Bullet had it relies instead on the pump rotors being lifted off the body when the pressure is too great. A little cretinous but I suppose effective. I discover further that my predilection for straight 50 mineral oil is also a potential cause of issues as the cold viscosity can overload the pump too. I fire off a new email to Mr H and crew with a mea culpa and set about checking to see if its run the big end. Seems with the piston and barrel off to be ok so I put it all back together again with the old pump spindle. What do I find though the pump jams at one spot. On careful examination it seems that the big piston on the improved scavenger pump is hitting the web on only one side of the pump body. I pair off the offending web with a sharp chisel and round it goes. Still clearly my fault as I should have checked that the pump turned ut a trap for young players and one to be careful of it yo intend to upgrade to the high capacity pumps. Seasons Greetings all.

[Dennis C]

Hi Simon

I have often wondered what people hope to achive by fitting these high capacity pumps for the very reason you state, if the bike has the pressure relief valve then it just opens and bypasses the extra oil, (nothing gained) if no pressure relief valve is fitted the valve lifts off its seat (not only is nothing gained it can't be good for the pump), also lets not forget these pumps are double action and pump on both strokes of the pump, so when the pump piston is going inward the valve lifts off but when the piston is coming outwards the pressure holds the valve on its seat, the result is a constantly varying oil pressure and a constantly varying load on the drive spindle. I would not fit one of these pumps to a bike without a pressure relief valve.

[Gwilly]

Respect Simon for admitting the error, pride usually forbids such disclosure.

Thereby we all learn.. So what caused the knock? The pump catching? Or the big end?

Any white metal in the return filter?

[Nettshubby]

Our hosts do advise checking for this very thing when fitting the new pumps, I recently saw this, I think on the tech section on lubrication.

[Nettshubby]

If you look at Technical Notes, and oil pump spindles, you will see the warning about clearance for the plunger.

[Nettshubby]

Sorry, that should read "Technical Notes, Engine, oil pump spindles.

[Nettshubby]

BTW, a pressure relief valve is available from our hosts in the accessory catalogue, I believe.

[Nettshubby]

It's in accessory shop under Engine, Timing side.

[Norm]

Sorry to hear this Simon, there is always some little trap to get caught with. I always rotate the spindle with my finger as I fit each pump because you don't want too much resistance on the spindle

[simon]

Yes it was simply a case of being too gung-ho. It's a personality trait I have to battle against. Seems I was lucky in that the big end seems fine and with the old spindle back in place with lighter oil it seems to be going fine. No signs of white metal and no other swarf other that the three or four teeth off the new spindle. As for the knock I can only assume it was either the dry big end or the spindle but it seemed to be more bottom end to me hence the strip down.