Oil pump plunger differences

[chris_cornwall]

My 18CS has been wet sumping and leaks oil from tank into sump when left for a few days and doesnt return all oil back to the tank when running.

So took the pump plunger out and its a bit worn and a couple of chips.

I ordered a new plunger from Jampot spares but its different

Both are the same in all aspects except one. The grove in the new one is only 2/3 the width of the original so the guide pin doesnt fit.

Did the design change at some point or is one wrong and the other right

What should I do

I'll post a photo on the photos section

[g80csp11]

012967 Plunger, oil pump, 2-start, 1948-63 £ 57.25 inc VAT
1948 up are two-start but with wide groove & floating pin

http://archives.jampot.dk/Book/Spares_l ... ingles.pdf
https://www.jampot.com/article_read.asp?id=519

[g80csp11]

should be wide groove , what part number did you order ?
your old one looks correct

[chris_cornwall]

Bwgger .... seen what I did

Ordered a 000770 WD

Will now get 012967

thanks

[SPRIDDLER]

My 18CS has been wet sumping and leaks oil from tank into sump when left for a few days and doesnt return all oil back to the tank when running.

Chris. Don't be too concerned. Most will 'wet sump' if left for a while. It's customary to drain the sump if the engine hasn't run for a while to avoid clouds of smoke or oil fouling the sparkling plug on start-up. If you've a couple of hours to spare and you've no more fluff to pick out of your jacket's Velcro search these Forums using the search words 'Wet sump'.
And there'll always be some oil left in the 'sump' because the return (suck) drilling in the crankcase is not right at the bottom: A bit like the dregs left in a milk shake which are unreachable by the straw