B25S Oil Drain-back

Here you can talk about all kind of TECH for the B50 B44 B25 And Other BSA unit Singles

Moderator: minetymenace

Post Reply
Cocker Cox
>40
>40
Posts: 42
Joined: Tue May 12, 2020 8:24 pm
Location: Barnsley oop norf
Has thanked: 8 times
Been thanked: 2 times
Flag: England

B25S Oil Drain-back

Post by Cocker Cox » Tue Jul 21, 2020 9:22 pm

Hi, All....

I’m familiar with oil drain-back (not wet-sumping as I believe this is a problem with the engine running), but I was surprised to find oil dripping out of the (disconnected) rocker box feed pipe on my B25SS (the bike had not been run for a couple of weeks and I was changing the oil lines, leaving the rocker feed pipe disconnected overnight). As the rocker supply is taken off the return, the only direct connection I can see between the main feed and the return is via the pressure relief valve. Can anyone enlighten me?

skippy
>1400
>1400
Posts: 1487
Joined: Mon Dec 19, 2011 3:25 am
Location: Horsham Vic Australia
Has thanked: 57 times
Been thanked: 14 times
Flag: Australia

Re: B25S Oil Drain-back

Post by skippy » Wed Jul 22, 2020 12:29 am

Any piping that is higher than the feed pipe will drain back out of the rocker feed pipe.
Which is the section of return pipe going to the oil tank that is above the rocker box pipe. If your tank is over full it will drain back through the return pipe till that pipe gets below the oil level in the tank.
Doug
Should never have sold them old motorbikes

Cocker Cox
>40
>40
Posts: 42
Joined: Tue May 12, 2020 8:24 pm
Location: Barnsley oop norf
Has thanked: 8 times
Been thanked: 2 times
Flag: England

Re: B25S Oil Drain-back

Post by Cocker Cox » Wed Jul 22, 2020 6:33 am

Cheers, Skippy. I appreciate that the system is one big u-tube, but just thought I’d check that it wasn’t indicative of a potential problem. Your reply sets my mind at rest! Thanks....

Post Reply