Ariel Owners Motorcycle Club

Hi All, Looking through all my bits to start building another engine and checking up on the oil feed to crank to from pump the tube which goes into the crank from the outer case is a slackish fit is there any way to alter the fit with a seal, I have tried another case and measured both tubes both are the same size but there must be a slight drop in pressure with the fit, I understand it has to have clearance between tube and crank but has anybody tried a seal or just leave as is. Clive.

The oil feed quill should be a tight fit in the case otherwise it could rub on the crank and wear away. Roller bearing engines require remarkable little oil, Grubby once broke a crank pin on his 350 and found that the crank pin had been fitted the wrong way round (prior to his acquisition) so no oil supply. He had ridden it 2000 miles.
So squirting oil in the general direction works well enough.

If, after decades of working fine, the Ariel Works would have found it necessary to fit a seal they would have done it.
With the pump pushing the oil down the quill there is also a slight 'suck' because of the centrifugal force the bigend creates.
The oil simply has no 'time' to escape sideways and back past the outside of the quill.
as Roger writes, singles need very small amounts of oil to stay working for long periods.

It gets enough oil with the current set up. Royal Enfields with their floating big end bush NEED pressure because it's a PLAIN bearing as do the ARIELtwins and fours. . As Vincent points out there's probably centrifugal force involved. Where singles have an oil pressure gauge it only reading a pressure that puts a load on the pump so it indicates "something" for your piece of mind. Nev

Hi All, Thanks very much for all replies, I had not really thought about it till I am about put together an engine to replace the old engine which need looking at after about 25years and I really don't know miles it has done.
I have a Triumph oil pump which I have modified to fit rather than going down the Morgo road it increases the pressure and return, both bore are larger but not to much, it needed cutting down and the plungers need brazing as they are hollow when you cut them but it can be done instead of fixing screws I used ground down allen bolts and slight indents inside the outer cover to suit I have one on the old engine for most of it's life and has not had a problem. Thanks for the replies Clive.

I have just measured the Triumph pump the pressure side is 7/16" and the scavenge side is 3/8" if that's any interest and the gasket needs altering so it will work, Clive.

Sorry all, The return side plunger on the oil pump is the larger of course still larger than the original if that's the way you want to try also the dural block is larger width wise and smaller height wise but there you go it's a project to try if you feel the need, Clive