[Rick Parkington]

Thanks, guys, some good points there that I think may provide the answer.
If RJBailey's bike over oiled when set on number three position, then it looks like the scavenge side of the pump isn't big enough to cope with full feed like most other bikes. As has been said before, Sunbeams were pretty good at making bikes so it seems unlikely that would make a crap pump and then try to cover it up with a wacky restrictor tap.
As Singleminded says, in the vintage era, mechanical (total loss/drip feed) pumps were generally backed up by a hand pump giving you the chance to give them an extra squirt in demanding circumstances - in effect over-oiling.
So I wonder whether the answer is that the pump was deliberately designed so that it was still possible to over-oil the engine, as in the hand pump days and the restrictor tap existed to control this feature.
Sounds reasonable.
Cheers Rick

[singleminded]

It's possible that the tap was a compromise carrying over from the drip control of the total loss system, maybe buyers of Sunbeams were happier knowing they could still control the oil flow..No more extra pumping of the tank pump the faster you went..Ducking rapidly now..

[rjbailey]

Here is my two penny's worth, my 29 9's regulator tap has the No1 soldered up and I usually run on 2 and all is well, how ever as some may remember, the other year on the Windsor park run she was laying down a smoke screen like a transatlantic convoy!! the cause, with out the specs on, turning the oil regulator the wrong way from 1 to 3 not 1 to2! This in no way answers Ricks original question as  to Why the regulator? but however it must have seemed like a good idea at the time! 

[Rick Parkington]

Ha ha, fair enough, Well as I said I have drilled the tap to no.2 setting so it should be okay - but I still don't see why only Sunbeam needs this restriction, unless the pump isn't quite adequate. As I understand it, scavenge pumps are larger than the feed side to cope with the greater volume of oil once it has frothed up in the engine and the fact that unlike the feed, it is working against gravity, so maybe your experience, Wessexman, indicates that the scavenge side is still a bit too small.
Anyway, your experience indicates it was worth the effort of restricting the tap of the bike I'm building , we'll see how it works out!
Thanks Rick   

[wessex_man]

I wouldn't increase beyond the no 3 setting size. This is the same size as the mains feed. In practice the oil should only spit back. I've blocked my no 1 off to stop wet sumping but you must remember to switch it back on and keep an eye on the tale tale. to ensure that the pump picks up.

If you do increase the size Yes you get increased oil flow and pressure and are unlikely to cease the engine. Quite the opposite in fact it's difficult to keep the top half oil free.

Even though the scavenge pump is greater than the feed you can get a lot of oil in the bottom half of the engine. the push rod tubes leak oil and the breather spits more oil than it should do on your chain or road depending where you've put it. This could lead to you giving your rear tyre a coat of oil and 'losing' oil from the tank on a long run.

Thought it was a good idea once now I know better.

[singleminded]

I think i ended up with a jet marked 35 I picked up at a jumble..I think that the pressure is also dependent on the condition of the mainshaft bush in the timing cover, I hope i never have to replace it..John

[Rick Parkington]

Thanks Paul and John,
I don't think it's to do with economy, Paul, because being as it is a recirculating oil system, not total loss, it shouldn't really make any difference unless it encourages the sump level to rise which shouldn't happen if the pump has been correctly designed - and it does have larger scavenge gears, so it should be okay.
John, yes I remember being puzzled about the rocker supply on my 9A too - it was even worse on a Series 2 Model 14 we had with an adjustable supply - you could really get that wrong!
The gauge is another funny thing, obviously you don't generally get much pressure with roller big ends as there is no real restriction so you could argue that a gauge is a pointless fitment. My friend Derek Bennett told me once that he fitted a too-long cork washer to his '35 Model 9 telltale and when he started the engine it just about blew the glass out of the gauge because the cork prevented the plunger from fully opening.
If you remove the telltale from one of these cases you can see that the hole for the rocker feed is inboard of the big end supply, so when the telltale begins moving, it opens the rocker feed first and the big end feed after, Derek's obstructive cork had prevented the big end hole opening, forcing all the pump output to the rockers, via the gauge, where back pressure from the restrictor jet in the pipe elbow caused the gauge to flip out.
It's essential to have a restriction at the rockers to ensure there's enough back pressure to fully open the telltale and feed the big end, so you need to find a setting (screw adjuster on the Model 14, jet on the 9) that provides adequate supply to the rockers with enough back pressure to ensure the telltale opens fully for the big end. Having achieved that, you just need to observe what the gauge says and investigate if it ever changes drastically.
The jet was missing from my 9A when I bought it as a project bike, which is why I had to look into it all - I think I  fitted an Amal jet but I can't recall what size. Since then I've learned that the standard jet seems to be a Binks #50 main jet - a pre Monobloc Amal 50 will do.
Sorry for the rambling reply but it  just occurred to me this might help someone, someday!
Cheers Rick 
 

[singleminded]

One thing I can say about too much oil volume, if the regulation to the rockers and valve guides is not right you get oil pouring down the barrel and also out of the silencer.
It took me a while to get that sorted on my 9A..I have heard that with a full flow tap the pressure can get above 60 psi, not sure if that's true mine is about 15-20 psi on number 2..John

[phutton]

I really don't know why the restrictions were thought necessary, but I tend to take the line that JML knew what they were doing! My guess is that it was all about economy - why use more expensive oil than you needed pottering around town, but open the flow up a bit for the week-end blast.

P.

[Rick Parkington]

Hello,
Does anybody know exactly why Sunbeam fitted the three position regulator tap? Back when I got my 9A I was advised that no. was never needed and to solder up the no.1 position to use as an off to prevent wet sumping, number 2 being satisfactory for all riding conditions. I know the theory is that no.3 is used when the oil is thick in cold weather but why have the restriction anyway? other manufacturers didn't. It's not like there's a risk of excessive oil pressure with a roller bearing big end and the scavenge pump is larger than the feed, which should prevent over oiling.
The needle goes up on the tank mounted oil pressure gauge when the tap is turned from 2 to 3 so clearly there is an increase in delivery. The reason I ask is that the 9 I am building at resent has a plain on/off tap and I decided to fit a jet in the inlet, equivalent to the number 2 regulator setting. But having done it I am wondering if it was worth doing. What's going to happen if you allow a full 1/ 4" bore feed to go into the pump?!
Anyone tried it...and lived to tell the tale?
Cheers Rick