Oil priming

[Phil C]

Is that part of the oil feed system? I thought that was some kind of pressure relief valve! I thought the ball and spring to prevent wet sumping were at entrance to the oil pump. As you can tell my knowledge is pretty sparse!   

Anyway, about the dia of the hole in the tap I've fitted - how small is okay?  I can't think Bernie would have recommended it if he didn't know it was fine.

Phil.

[berniej]

I've had these taps fitted to A50, A65 and M21 for several years and never had a problem. Return flow to the tank has always been as expected.

Phil, remember that you will only get a steady flow of oil from the return pipe when the sump has more oil in it than is usual during riding - due to wet sumping or priming. Once a steady state is achieved with the engine running the scavenge pump will be slurping at the surface of the oil in the sump and returning a bubbly mixture in spurts. That's usual and a sign that the scavenge flow is healthy.

Cheers,
Bernie

[Phil C]

Hi Bernie, Thanks for the assurance that these taps are okay. 

Two questions:

1.Just checking I've definitely got the right tap (see photo on recent post), the hole in the middle is quite small, yes?

2. The oil I see returning into the tank, when I turn the engine over with the kickstart, appears to be bubbly, so that's okay, but rather than a spurt it's a slow dribble. Is that to be expected, given that I'm just turning the engine over by hand, with the kickstart,  rather than starting the engine? (I haven't started it yet since I fitted the tap.)

Phil.

[JulianS]

Bubbles on return normal because the scavenge side of the pump has larger gears than the feed side so draws aerated oil.

[berniej]

It looks exactly the same as those that I use. I would suspect that the hole through the valve ball is no smaller than those through the oil feed union and crankcase oilways leading to the pump inlet....

Cheers,
Bernie

[Phil C]

Thanks Bernie.

Any thoughts, anyone, regarding my question (above) about a dribble rather than a spurt? 

Phil.

[Phil C]

I have no reason to doubt Bernie, and I am very grateful for his help again, but I am still a little bit nervous about the size of the hole that goes through the middle of the tap, especially as Julian says that  any constriction is a risk. So I might check the diameter of the hole tomorrow and ask for comments.

A further thought: there must be lots of people using taps on the oil feed, in order to prevent wet-sumping.  What kind of taps are in use, and what diameter hole goes through the middle?

Phil.

[JulianS]

Oil return on kickstarter will be lower than you would see with engine running due to rpm difference.

[Phil C]

Hello everyone,  A bit concerned about the size of the hole in the tap I've fitted on my oil feed, I've just been checking hole diameters. 

The  inside diameter of the tube which fits up to the oil tank (with the union nut on it) is about 0.242" (6.1mm.) That's the same as the i/d of the bit of copper tube I put in the downward side of the tap, over which the rubber pipe fits.

The hole in the middle of the 8mm ball valve tap I've fitted is about 0.187" (4.8mm.)

So, roughly speaking, it's 1/4" and 3/16".

Would that degree of constriction be an issue?  I'm inclined to think it would be okay, but then I know next to nothing, so would be grateful for opinions. Bernie has used these taps with no problem, but Julian says any constriction is a risk. Now we know the degree of constriction, and thoughts please?

Phil.

[berniej]

FWIW I'm stripping my B40 at the moment and here's a pic of the oil union.

I can just get a 4.5mm drill bit in the holes, a 5mm won't go. The bores of the copper pipe are larger and those of the flexible pipes larger still.

[Phil C]

Thanks Bernie.  So, if I am understanding this correctly, and assuming my bike is like yours, the hole through the middle of my new tap will not be the narrowest part of the oil feed. In which case (provided I remember to turn the tap on each time before I start the bike) it should be safe to use the tap.  Does anybody disagree?   Phil.