AJS & Matchless Owners Club

none of my singles have ever wet sumped.
I do leave them with the engine coming up to TDC, to ensure both valves are shut.
It would seem this leaves the oil pump parked in a favourable position.

and of course all of them run on that unmentionable thick stuff not the stuff with the consistency of cats piss.

quote:
none of my singles have ever wet sumped.
I do leave them with the engine coming up to TDC, to ensure both valves are shut.
It would seem this leaves the oil pump parked in a favourable position.

and of course all of them run on that unmentionable thick stuff not the stuff with the consistency of cats piss.

I have seen this solution quoted quite often , but it doesn't seem to make any sense because the oil pump position is only related to the position you fitted it originally ?
Or is there something I'm missing.
I'm not saying it doesn't work just interested in why.

Ian

I agree, it doesnt make any sense and I have no idea why it works.

Its a tip handed down over the years by various riders.
Fact is it works for me. For me thats good enough.

Hi All,

I've heard of leaving it on compression as well but also remember reading something about the reasons and did a search and came up with this:

https://www.jampot.com/article_read.asp?id=151

It explains the reasons for the wet sumping a bit more. You may not have to go to the trouble to add the indicator probe if leaving it on compression does the job but at least the article sheds some more light.

I remember seeing another writeup of someone who had added a perspex pump cover plate so they could see the pump position for the same reason.

Regards,
LanceEdited by - Lance on 02 Mar 2011 4:00:33 PM

quote:
I have seen this solution quoted quite often , but it doesn't seem to make any sense because the oil pump position is only related to the position you fitted it originally ?
Or is there something I'm missing.
I'm not saying it doesn't work just interested in why.


Maybe oil leaks (syphons?) past the pump plunger whatever its position, so, it may be now't to do with the pump plunger position at all.
Here comes a wild off-the-cuff thought: Could it be that when the piston is left at TDC the big end is higher than the plunger and c/shaft axle but when it's at BDC, it's at the same height as or lower than the pump plunger and axle?
Go on then, shoot me down, or provide a better theory

Like the theory Nev, but the oil tank is still much higher than the crank at TDC and so will still drain by gravity. Mine has never wet sumped regardless of what position the crank is left.

Yebbut there's still a greater head of oil at BDC than TDC...?
Pass.

Atcherly, my '54 has never wet sumped either, but I did fit a new oil pump plunger when I rebuilt th'engine when purchased 5 years ago, after leaving the (previous owner's) anti-wet sumping tap shut for about 10 miles.

Just come across this anti-sumping valve which you can't forget to turn on.
Never seen or used one.
Caveat emptor!

http://cgi.ebay.co.uk/BSA-CLASSICS-ANTI ... 5d2dc05ee8

Another (my) provocation: www.fotos.web.de/ajay01/ANTI_WET_SUMPING_TAPEdited by - PGGuse on 05 Mar 2011 11:08:49 PM

Yes, I know this solution but my magnet has a cap with a button for turning off the engine. I would have to replace the cap, but I do not know which one is right, my cap is attached with two screws those with external contact are usualy have thread.