Wet sumping

Just catching up on things and read all the posts on oiling problems.
I suffered a great deal of frustrations earlier this year with oil return and wet
sumping on my B50. In the process of trying to find the problem I talked with a lot of
very helpful people and read a lot of emails. One potential problem I learned about that
has not been mentioned here, and I have no idea if applies to the pre unit twins or not.
On the B50 oil pumps it has been found that if the resistance is increased in the return
line and the tolerances on the oil pump are out of spec it possible for the return pump to
push the oil back up the shaft and into the feed chamber and then back to the motor.
The cure which has worked for more than one person (both with oil filters fitted)
I talked to, is to machine the oil pump casing and fit O Ring seals on the shaft.
I did this mod to my oil pump, it was easy to do and looks to be an improvement over
the standard. However this was not my problem, my problem was way simpler but took me
several weeks of rebuilding oil pumps, checking oil filters, oil lines etc.
Not all BSA oil sump covers are the same depth, having various engine parts laying
around I had fitted the sump cover from one of the other engines, looks the same but is
just shallower enough to almost block the B50 suction tube completely.
So obvious afterwards but it was the last thing I checked. Thought I'd post this
information, might help somebody sometime.

Roger Brown Calgary, Alberta

I had a perfectly built bench motor that had the timing and drive sides stripped
down twice on a cold gararge floor before I found the dicrepancies in the sump covers.
The O ring modifications are the research of Rick the mechanic at Rabers in California.
The other B50 specific I learned is that not all B50's have thrust washers in the oil pump,
this was causing me concern but I have about 1,200 miles on the bike now and no wet sump
problems at all.

Mail to Roger Brown

Look also on Racing mods page.
There are also a sulution on the wet sumping. (Figure 1)

Updated 23:12 2004-01-12
© Rickard Nebrér