Bigger oil return pipe ?

[Yoozy]

Some bikes I've seen look like they have a larger bore oil return pipe, #49. I've looked for the mod, is it there, does it work, what's the benefits ?,,,,,,,,,, or am I going potty

[Mincehead]

Well, you COULD increase the volume of the oil return but it may not bring any benefit.
In fact, you may actually increase the load on the return oil pump because there will be a larger volume of oil (head in weight) to move so it `may` stress the pump and gear.
Generally playing with oil line volumes is not recommended unless you know how to do the math to ensure you`re not creating a problem that didn`t exist before.

[Yoozy]

You gone all Murcun Mince

[Mincehead]

Murcun, American?

[Yoozy]

Murcun, American?

Eye.

[Mincehead]

In what way, what makes you say that?

[Yoozy]

In what way, what makes you say that?

Well, you COULD increase the volume of the oil return but it may not bring any benefit.
In fact, you may actually increase the load on the return oil pump because there will be a larger volume of oil (head in weight) to move so it `may` stress the pump and gear.
Generally playing with oil line volumes is not recommended unless you know how to do the math to ensure you`re not creating a problem that didn`t exist before.

[Mincehead]

Math? Generic engineering term simply meaning `calculations`.

[Kayla]

It's 'maths' or 'mathematics' in British English, 'math' in 'Merkin

[Yoozy]

Just called 'sums' round ere.

[Rod.s]

If you increase the diameter of the return line you will decrease the pressure, which will give you the same or very similar volume. To increase the volume you need to increase both the pressure from the pump and the dimeter of the return line.

The only real way to understand this is to fit a pressure gauge to the return line and measure the pressure at the pump, find out the viscosity of the oil and then do some maths/mathematics/calculations/scribbles and lots of guess work....

This is a good place to start, the pipes end pressure is 0....

http://www.pipeflowcalculations.com

If you are worried about oil flow to the crank whilst racing, I would start by examining the oil tanks pickup, ensuring that the pickup is never staved of oil from high cornering forces. Baffle the tank and extend the return line so it empties into the baffle with the pickup.
Remembering that the oil return tank is just a storage for excess oil, by giving the pickup line the maximum available oil the excess will simply overflow the baffle and fill the remainder of the tank. Do a web search on making baffles, the mouse holes in the bottom of the baffle need to be big enough to allow flow at start up but small enough to resist emptying the baffle box at under cornering/braking "G" forces.

Secondly remove the crank and fit all new bearing shells, this will reduce the tolerance and also reduce pressure/volume wast.
re-shim the big ends and the crank to remove all but necessary end float, when shimming use minimum factory tolerances.

Rod

[misterdimwiddy]

If you increase the diameter of the return line you will decrease the pressure, which will give you the same or very similar volume. To increase the volume you need to increase both the pressure from the pump and the dimeter of the return line.

The only real way to understand this is to fit a pressure gauge to the return line and measure the pressure at the pump, find out the viscosity of the oil and then do some maths/mathematics/calculations/scribbles and lots of guess work....

This is a good place to start, the pipes end pressure is 0....

http://www.pipeflowcalculations.com

If you are worried about oil flow to the crank whilst racing, I would start by examining the oil tanks pickup, ensuring that the pickup is never staved of oil from high cornering forces. Baffle the tank and extend the return line so it empties into the baffle with the pickup.
Remembering that the oil return tank is just a storage for excess oil, by giving the pickup line the maximum available oil the excess will simply overflow the baffle and fill the remainder of the tank. Do a web search on making baffles, the mouse holes in the bottom of the baffle need to be big enough to allow flow at start up but small enough to resist emptying the baffle box at under cornering/braking "G" forces.

Secondly remove the crank and fit all new bearing shells, this will reduce the tolerance and also reduce pressure/volume wast.
re-shim the big ends and the crank to remove all but necessary end float, when shimming use minimum factory tolerances.

Rod

Your comment caught my eye after my recent crank blow up.

Not so sure that crank/rod end float would influence oil pressure? More down to the journal clearance and the pump being healthy.

Also the two pumps are doing quite different jobs (as you indicate I think).

One pump is taking it's feed from the sump, through the strainer, returning oil to the tank and the other is fed from the tank to supply the oil galleries. The pick up filter for the pump supply is located at the lower level of the back of the tank and so to suffer starvation the tank level would have to be extremely low. Also I imagine the tank routinely runs at a high level if the return pump is functioning correctly because otherwise it is not much of a dry sump? 4 litres of oil is a large quantity and it would be nice to know how much is actually within the motor rather than sitting in the tank.

You may be right in suggesting that baffles would prevent surge but I have not seen my oil light blinking under hard braking before.

New crank shells for me and pumps that are in better nick I hope will prevent a repeat of my LH big end failure. Watch this space.

[Rod.s]

If you increase the diameter of the return line you will decrease the pressure, which will give you the same or very similar volume. To increase the volume you need to increase both the pressure from the pump and the dimeter of the return line.

The only real way to understand this is to fit a pressure gauge to the return line and measure the pressure at the pump, find out the viscosity of the oil and then do some maths/mathematics/calculations/scribbles and lots of guess work....

This is a good place to start, the pipes end pressure is 0....

http://www.pipeflowcalculations.com

If you are worried about oil flow to the crank whilst racing, I would start by examining the oil tanks pickup, ensuring that the pickup is never staved of oil from high cornering forces. Baffle the tank and extend the return line so it empties into the baffle with the pickup.
Remembering that the oil return tank is just a storage for excess oil, by giving the pickup line the maximum available oil the excess will simply overflow the baffle and fill the remainder of the tank. Do a web search on making baffles, the mouse holes in the bottom of the baffle need to be big enough to allow flow at start up but small enough to resist emptying the baffle box at under cornering/braking "G" forces.

Secondly remove the crank and fit all new bearing shells, this will reduce the tolerance and also reduce pressure/volume wast.
re-shim the big ends and the crank to remove all but necessary end float, when shimming use minimum factory tolerances.

Rod

Your comment caught my eye after my recent crank blow up.

Not so sure that crank/rod end float would influence oil pressure? More down to the journal clearance and the pump being healthy.

Also the two pumps are doing quite different jobs (as you indicate I think).

One pump is taking it's feed from the sump, through the strainer, returning oil to the tank and the other is fed from the tank to supply the oil galleries. The pick up filter for the pump supply is located at the lower level of the back of the tank and so to suffer starvation the tank level would have to be extremely low. Also I imagine the tank routinely runs at a high level if the return pump is functioning correctly because otherwise it is not much of a dry sump? 4 litres of oil is a large quantity and it would be nice to know how much is actually within the motor rather than sitting in the tank.

You may be right in suggesting that baffles would prevent surge but I have not seen my oil light blinking under hard braking before.

New crank shells for me and pumps that are in better nick I hope will prevent a repeat of my LH big end failure. Watch this space.

Mate I'll reply in a few day, bloody hard to type with my right hand in plaster and my left shoulder throbbing like a bastard!