Britbike forum

Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supplyJob Cycle

Upgrade to Premium membership HERE! Premium Membership

New Sponsor post
15% Off Black Friday Sale
by The Bonneville Shop - 11/24/22 5:51 pm
New FAQ post
Member Spotlight
Spitfire Ken
Spitfire Ken
Posts: 378
Joined: April 2013
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
kevin 55
Top Likes Received (30 Days)
Bry 24
Newest Members
Hedgehog65, NDarwin, Bas classic bikes, lojo, Doug McLaren
12,333 Registered Users
Who's Online Now
4 members (Jon W. Whitley, Magnetoman, DMadigan, koan58), 16 guests, and 40 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Most Online204
Jul 10th, 2022
Thread Like Summary
Allan G, Gordon Gray, Peter640, Stuart Kirk
Total Likes: 20
Original Post (Thread Starter)
#889149 08/24/2022 5:36 AM
by Peter640
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!
Liked Replies
#889173 Aug 24th a 08:03 PM
by Stuart Kirk
Stuart Kirk
+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.
3 members like this
#889162 Aug 24th a 02:57 PM
by gunner
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.
2 members like this
#889183 Aug 24th a 09:50 PM
by Steve Erickson
Steve Erickson
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...
2 members like this
#890513 Sep 11th a 11:17 AM
by Peter640
Thanks Stuart. She fired up easily tonight and nice steady oil return. Looks prettier with the distributor (albeit non functional ) in place!

2 members like this
#889189 Aug 24th a 10:33 PM
by Stuart Kirk
Stuart Kirk
Originally Posted by Peter640
...... I fear I have an oil pump issue.....
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!!
1 member likes this
#889188 Aug 24th a 10:31 PM
by Dave Martin
Dave Martin
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.
1 member likes this
#889229 Aug 25th a 12:38 PM
by Lannis
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....

1 member likes this
#889414 Aug 27th a 10:36 PM
by Stuart Kirk
Stuart Kirk
Originally Posted by kommando
.......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. ........Never have sorted out the root issue .........
That's pretty odd. Those springs are really light. I wonder if you somehow got one that was too strong?
1 member likes this
#889389 Aug 27th a 03:04 PM
by kommando
Originally Posted by Peter640
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.


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.
1 member likes this
#889432 Aug 28th a 03:50 AM
by Stuart Kirk
Stuart Kirk
Originally Posted by Peter640
....... assume I pull the two bolts and wriggle the pump out via sump? .......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!............
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.
1 member likes this
#889434 Aug 28th a 04:35 AM
by Dave Martin
Dave Martin
dunno if this helps ....... 13mins onwards

1 member likes this
#889472 Aug 28th a 11:03 PM
by Stuart Kirk
Stuart Kirk
Originally Posted by Peter640
Dave thanks......It looks as if the pump is only accessible with the inner gear box cover off.........
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.
1 member likes this
#890341 Sep 9th a 06:57 AM
by Peter640
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!! smile ]

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

BSA all the way!

1 member likes this
#890497 Sep 11th a 03:56 AM
by Stuart Kirk
Stuart Kirk
Well done. Good detective work.
1 member likes this
#890574 Sep 11th a 11:37 PM
by Stuart Kirk
Stuart Kirk
Originally Posted by Peter640
.... Looks prettier with the distributor ..... in place!........
My first BSA was a 1961 C15S. I rode that thing everywhere.

Hoping to recall old memories viewing the complete bike, I went to have a look at the dropbox file but all I got was 2 of what seemed like Chinese characters. Oh well. Maybe try Postimage? It works really well here.

Oh, another thing. You could machine up a tach dive to go where your distributor goes since you don't use it now, and then you would have a C15 with a tach! That's exactly what I did on my 1965 C15FSR side points bike. That year had a threaded cap where the distributor used to go. I'm sure folks noticed but nobody EVER said anything. (It was rather easy project to do on a lathe.)
1 member likes this
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor

© 1996-2022
Powered by UBB.threads™ PHP Forum Software 7.7.5