BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: cee-b on 25 July, 2017, 19:16:13

Title: C15 oil feed problem
Post by: cee-b on 25 July, 2017, 19:16:13
Hi,
I have recently bought s 1961 C15T and have a problem with the oil feed.

The oil pipes are routed according to the w/shop manual. The pipe from the return pump goes to a to a T piece, with one line leading to the tank and the other to the top end of the engine.

The problem is that all the oil is being scavenged to the tank and none is going to the top end. I cannot see why it should. Despite this being the way the manual says it should be 'plumbed', I can't see why the oil would continue uphill to get to the rockers etc, when it has an easier route to just return to the oil tank.

What am I missing here??

Col
Title: Re: C15 oil feed problem
Post by: SUPERGRUMPS on 27 July, 2017, 19:20:36
mine is the same, but it does work, I think its just a case of pipe diameter, and a smoother internal bore, hence the use of copper. Tthere will be less resistance in the copper pipe leading to the rockers, so enough oil will get to. can only suggest you have a slight blockage or the copper pipe may be kinked on route. 
Title: Re: C15 oil feed problem
Post by: cee-b on 27 July, 2017, 22:33:41
Thanks for the response Grumps, I was wondering if it might have something to with diameters and relative resistance to flow.

The bike has been extensively messed about with and 'restored' by the previous owner(s) and the oil pipes are now mainly clear plastic tubing.

The return to the tank is full bore of the plastic pipe, but the line to the headers goes into a length of the original diameter copper pipe, which is considerably smaller. Exactly the opposite way around to how it needs to be.

It looks like I need to do some 'fettling'
Title: Re: C15 oil feed problem
Post by: om15 on 28 July, 2017, 09:49:42
I think that the answer may lie with the actual return tube in the oil tank, if you look at the return oil flow with the engine idling it indicates that the hole in the tube is much smaller than the internal bore of the oil line, if this is the case it will create a back pressure, and the oil will take the line of least resistance and flow up the line to the rocker feed.
Title: Re: C15 oil feed problem
Post by: cee-b on 28 July, 2017, 14:44:59
Thanks OM15 (ex-RAF 'rigger' by any chance?).

I have put a smaller sleeve inside the the tank return and it has achieved exactly that. I now have a nice balance between scavenge and feed to the rockers - happy days.
Title: Re: C15 oil feed problem
Post by: om15 on 28 July, 2017, 17:47:04
Yes I was an RAF rigger (1968 to 1977), still doing it - until November when I thankfully retire. :)