I'm rebuilding a b25 starfire engine. The ball bearing in scavenge non return valve is missing.
I can see I cab get a replacement easily enough but can't see how to remove the old one and replacement the new one.
Does anyone have any tips?
Regards
The scavenge ball valve suction tube in the sump is a press fit into the crankcase and is not meant to be removed. If there is no ball in yours it was probably ommitted by BSA! The only way I've found to remove the aluminium pipe stub is to drill it out and fit a replacement as these are sometimes available.
Definitely check the ball is missing before doing anything drastic, and source a replacement before reaching for the drill.
Thanks for that Rupert. It's definitely missing. I presume it must have been missing from manufacture as it's impossible for it to fall out.
Replacements seem to be readily available but I'm loathed to try to replace it really through fear of damaging the crankcase or the new one not fitting or something.
Am I right is saying that the only consequence of it not being there is that oil in the return pipe to the tank and the feed to the rocker will flow back to the sump?
It's definitely not a job I would tackle with a hand held electric drill! Use a pillar drill and bolt the crankcase upside down on the table. File the angled end of the valve level and start with a 6.5mm drill, then gradually enlarge .5mm at a time until you can see you are close to breaking through the outer surface of the valve. In terms of depth for starters, only go as deep as necessary to stop before the crosswire which retains the ball. When you can see enough of the crosswire punch it inwards to get it out of the way of the drill so you can go a bit deeper. Drill not much past the crosswire in depth and enlarge the hole till you can see the inner end of the valve - then you know how deep to drill without drilling into the crankcase itself.
Yep, the valve stops oil draining back to the sump from the return pipes, in doing that it also keeps the scavenge side of the pump primed with oil.