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You know when you’ve just finished a build and you have a crisis of confidence!

Mine is with the oil feed and return pipes on the bottom of the motor!

I am sure feed is RHS and return is LHS as you sit on the bike.

Early 1961 C15 engine. I’d love reassurance I have it right before I start it up! I’m finding neither Haynes nor Rupert Ratio are super clear!

Sorry for a basic and dumb question!

Peter in Sydney!

My reading of the Rupert Ratio manual is that models with a rectangular sump plate have the oil feed on the outer side of the engine and the return side on the inner side.

Later models with a square sump plate have the pipes reversed with the feed on the inner side of the engine and return on the outer side.

Since your bike is an early C15 you should have a rectangular sump plate and the oil feed is on the engine's outer side. See page 37 in the lubrication section of the RR manual.

+1 on gunner's suggestion.

And to absolutely confirm it for your own peace of mind, disconnect the lines and fill each one from an oil squirt can then kick the engine over (spark plug removed) and watch the lines to see what happens. The feed line will draw oil in and the scavenge (or return) line will blurp oil out.

Thanks Stuart and Gunner. I fear I have an oil pump issue.

Thanks for help.

Peter

If your stripping it apart again to look at the pump. Spin the pump up with some flexible hose and a drill, put the supply line into some oil and spin the pump up. It will prime the system and make sure the oil is nicely coated around the big end (if your C15 runs shells).

Be patient when testing. I've found sometimes it takes quite a while to actually get the oil moving. If the bike is still assembled, put it up on the center stand in gear and spin the rear wheel (plug out, of course).

Kicking it will work eventually, if all is good. But I've found the energy expended in the 50+ kicks exercise requires at least 3 beers to recover from. Spinning better...

A thing I do when first turning the motor over on my unit singles is to remove the cover over the alternator and turn the motor over (with the plug removed) with a suitable socket and socket driver in my cordless drill on the crankshaft nut. Yu can get a fair lick of speed without the expenditure of much energy! more than tick over and certainly enough to ascertain correct oil flow. Just make sure you get the direction of rotation right.

This has occasionally got me thinking of electric starts (with the deco lever), but then nah, the idiosyncrasies in starting these bikes is the best security system there is.

You may or may not. The squirt can test will give you a clear sense of that.

Did anything at all happen to the oil you squirted into the lines when you kicked it over? If you fill them to the brim and nothing happens with either one that could mean the pump isn't turning. That would be fairly unusual. If only one line shows some kind of activity, that could be internal to the pump or a line blockage.

Was anything capped off or plugged during work to keep debris from getting inside the engine? I've seen those sort of things overlooked. Heck, I've done it myself!!

Thanks all. The plot is thickening as I have tested the lines and they are correctly connected and there is movement of oil in the right direction when kicking over with the plug out.

I removed the sump plate and pushed the wire up the scavenge pipe and cleaned out by spaying some parts cleaner up there. I am sure I can feel the ball bearing that forms the non return valve moving.

I ran a clear pipe to the scavenge pipe and got good suction so I left the sump open and that pipe connected then hooked the feed pipe up and started the bike with the extended scavenge pipe in a bowl of oil. Oil flowed freely in and out the motor and strong returns to the tank. Momentary success!

Yippee I think so bolt all back together. Start her up and have strong return flow to the tank for about 30-40 seconds before the flow stops.

I repeat what I did before but no flow! I’m thinking the oil pump has decided to stop working. Totally frustrating as the bike has been a major rebuild!

Not sure what else to do but expose the pump and pump drive mechanism to see what’s going on. Bugger!

Could there have been something on the sump plate which has been sucked up and blocked an oilway?

I think from reading the description that you repeated the steps starting from cleaning the suction pipe. Is that right?

It was all cleaned out very thoroughly but it is a possibility, it would explain the intermittent nature. The other option is if the ball in the return valve is sticking on the downstream or pump side of the valve and blocking the oil from entering the pump on the return side?.

I'm going to go for a ride the next few days and i'll mull my options over before I start pulling the timing see apart! Ill also drop by a pal's place who's a much better mechanic than me tomorrow and ask for his advice!

It is weird that it works fine then stops. The oil flow was super good for the 30-40 seconds it worked then nothing in or out. I wonder if removing the distributor has caused the drive gear to move? I may have to try with it reinstalled?

Any way lots to think about as I head up thunderbolts Way tomorrow!

See you soon and thanks for the call today.

Peter

But don't all dry sump bikes work that way? You would expect the return side of the pump to squirt oil until it empties the sump, then quit until the pressure side of the pump refills the sump? It ought to then steady out at an intermittent dribble into the tank....? The pressure side of the pump can never keep up with the return side....

Lannis

"The other option is if the ball in the return valve is sticking on the downstream or pump side"

I once had this happen because the little bar in the pickup valve had broken allowing the ball to be sucked up and block the passage way. As soon as the motor stopped it fell back down and all appeared to be fine. At low revs or kicking, all seemed well until the bike wet sumped like crazy with a few revs, which of course cleared when I next started the bike at tick over...... took me a while to work that one out!

If the distributor point cam turns and it fires up, the drive is working. Also, the pump is known for coming loose but that's not likely if the engine is freshly built.

Are you absolutely sure the feed side isn't working? It will take a little while to fill the sump enough for the return to pick it up and start showing return oil spurting in the tank. You could remove the pressure relief valve and see if any oil comes out when kicked over to verify the feed side.

Also, you could prime the crankcase by squirting a bunch of oil in through the valve inspection caps. It will slowly trickle down into the crankcase (Give it a few minutes.) then the scavenge pump can pick it up quickly if it's working ok.

I have a 59 C15 engine, the first time I rebuilt it I luckily did with feed and return pipes made from clear pipe. When I started the engine the return was good as I had primed the engine, then it stopped totally. Re-primed the sump and started again but also looking at the feedside pipe, this showed flow in the right direction for a few seconds, it then stopped moving before then reversing with bubbles of air showing.

After 3 more strip downs and reassembly the only fix was to remove the anti wet sump ball and spring out completely and replace the bung. This anti wet sump valve is after the pump only accessable from inside the cases with crank out. I fitted new ball and spring, re-seated the ball with drift and hammer, checked it opened using an can on the oil feed hole the pump feeds into on the timing side case which it did. But the same symptoms were there every time until I took the ball and spring out.

Never have sorted out the root issue but it does put the allegedly golden rule that the gear pump will always push oil forwards until the pressure is high enough to clear a restriction out to grass. Well it has a go but once it meets stiff opposition it gives up and forces oil backwards while sucking air in through any gaps.

That's pretty odd. Those springs are really light. I wonder if you somehow got one that was too strong?

[quote=Stuart Kirk]The pump is easily removable from underneath. Also, the pump is known for coming loose but that's not likely if the engine is freshly built [quote=Stuart Kirk]

Thanks Stuart, assume I pull the two bolts and wriggle the pump out via sump?

At least I can then pull it apart to see if there is a fail inside.

It’s a year since I built the motor so I’m buggered if I can remember if the pump was mounted via sump or inserted into timing side crank case! The joy of an ageing & decaying brain!

Peter

I'm going from memory too. The last bushing C15 I built was around 16 years ago. So, if I remember right, there are 3 screws holding the pump into the case and 2 more holding the three pieces of the pump together. It should come out the bottom through the hole the sump plate covers. Of course, once the pump is removed, all the oil in the tank will start draining out so it's good to empty the tank first or at least pinch the line.

dunno if this helps ....... 13mins onwards

No used the right spring and tested the ball lifted when pressure was applied. Changed oil pumps too.

Dave thanks that video is a most helpful reminder. I am pretty sure we’re back to the bench! It looks as if the pump is only accessible with the inner gear box cover off. I am now wondering if there may be some material in the oil ways. Before reassembly I flushed with hot water and air but …. as the lawyers say, “Res Ipsa Loquitur” ie the facts speak for themselves!

Peter

Big apologies for raising false hopes here. Teach me to trust memories from 16 years ago. I should have dug out a c15 case and pump to check before saying anything.

The thing is, Gold Star pumps DO come out the bottom and I guess that's what I was thinking of. So why would BSA change such a nice feature on their new modernized single? Go figure.

No stress … it’ll keep me busy when I am back home! 😂

Peter

After a monster frustrating couple of days in the shed .... all is now revealed! Gosh its hard to get the inner cover off with to expose the oil pump. The dowels were super tight and in the end I had to pull the clutch to tap the drive side end of the main shaft (gently) to get things moving!

When I rebuilt the motor and used a modern Electrix generator and ignition. This meant there was no need for the old distributor that is driven by the top of the same shaft that drives the oil pump. That shaft is held in place by a bush, that in tern is held in place by a small grub screw that locks it into place.

When I assembled I didn't drive the bush (40-0428) down the shaft far enough, so the grub screw missed its point of interference and when the bike started the shaft (40-0438) could drift north by about 6-8 mm and disconnect the drive to the oil pump! When the motor stopped the shaft slipped back down and engaged with the oil pump!

So when I turned the motor over the pump looked like it worked. when I started the bike the pump worked for about 20 seconds then the worm gear moved north with the shaft and disconnected, so no drive to the oil pump!

Faaark! Who'd of thought it.

Luckily with all that moving about no damage seems to have been done!

So the solution is ....

1. Drive the bush home properly and secure with grub screw. It might make sense to pop a small drill bit thru to mark the bush thru before the grub screw is inserted so it can seat its self more securely into the bush and stop it moving. It must be under some light load.

2. Re-install the distributor, even though its not needed, its physical presence will stop the shaft from moving and i'm not that confident that solely relying on the grub screw to lock the bush in place is sensible when the distributor is left off the bike.

Anyways more grist to the knowledge bank mill. The critical thing here is driving that bush all the way home. It is what stops the shaft moving. On re-reading Ruper R he, of course, does give me this tip! [no points for being right after the event!! ]

If I could id post some pics but I haven't mastered that yet!

BSA all the way!

Peter

This might work!

https://www.dropbox.com/s/ezx2yu1bopmz772/photos.url?dl=0

Peter