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Allan G, Nick H, The Bonneville Shop
Total Likes: 3
Original Post (Thread Starter)
#841552 03/01/2021 7:55 PM
by RF Whatley
RF Whatley
1972 OIF A65L with a strange issue.

If you ride this bike 7-10 miles all the engine oil exits the breather. In other words it oil wet sumps and all the engine oil ends up being dumped. Bike has had the oil pumped swapped and the result is the same. Oil feed and return system is clear and seems to be in good working order. Gauges have been applied and the correct pressures and vacuums are present.

New owner (one week) has no experience to share, but has told us that the engine had recently been "rebuilt".

Our Theory: We highly suspect that a novice engine builder left out the breather timing disk, and without the disk that the oil is free to leave the engine. BUT in order to test this theory we'd need to pull the engine out of the frame and all the way apart, which is obviously a HUGE step just to check our theory.

So we're looking for someone who has experienced this symptom before. Do you know anyone who left the breather valve out of an A65 and what was the result ??

Thanks in advance for any help. thumbsup
Liked Replies
#842009 Mar 5th a 06:02 PM
by RF Whatley
RF Whatley
Originally Posted by Nick H
Just stumbled on this wet sumping tech article at JRC site.

Thank you for the very thoughtful link. I don't want to seem unappreciative. However, the BSA uses a gear pump that presents a whole set of different issues from the Triumph's piston plunger pump. Whereas the Triumph is more likely to oil wet sump going down the road, the BSA is more likely to oil wet sump only during long storage.

It's quite common for Triumphs to loose oil return ability due to small bits of trash in the pump's check valve. The gears in the BSA pump will pass that type trash right on through. So it's completely opposite.... which is the basis for all the head scratching.

All the best. thumbsup
1 member likes this
#842565 Mar 11th a 07:51 PM
by The Bonneville Shop
The Bonneville Shop
We had a customer experience a similar situation on a 1968 Triumph 650 recently. Upon start-up, everything was fine until about 20-30 seconds after running. Oil started to belch out of the breather tube. An immediate check of crankcase oil contents revealed about 5 or 6 ounces drained from the bottom end. 100cc was then replenished through the timing hole aperture. The engine was started again, and sure enough, excessive oil blowing through the breather outlet hose again. The curious thing was that there was some oil returning to the oil tank, although a lower volume. After a lot of head-scratching and cussing, it was revealed the customer had replaced the original sump filter/drain plug with a shiny aftermarket plug complete with a magnetic insert. The scavenging pick-up tube was very close to the magnetic insert, effectively reducing the oil evacuation, and causing the crankcase to fill with oil. This was proven when the customer reverted back to the original filter/drain plug assembly.
-Dave
1 member likes this
#842568 Mar 11th a 08:13 PM
by htown70
htown70
I had the same problem. Check ball in return pipe sticking due to magnetic drain plug directly underneath it on cheapo aftermarket sump plate. I switched to one from SRM that has the drain plug in the back of the plate away from the return pipe. No more problems.
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