Greg,
Did you calculate the 15 turns or is that written somewhere?
ET: Engine (Twin) Oil pump volume
- Thread starter Cyborg
- Start date
Did you calculate the 15 turns or is that written somewhere?
Someone on here posted that info........I'll be assembling an engine this week, so I could check for myself......although it sounds about right.
Always make sure there is a good glassful of oil in the bottom of the crankcase.......especially on a new engine build and after every oil change......I tend to also prime the oil system from the filter housing and the galleries of the timing cover.......remove the acorn nut and jet holder atop the timing cover and squirt oil in there several times to bleed oil into the galleries........pumping some oil from an oil can down each pushrod tube is the easiest way to fill the lower case and helps the cams/followers which is critical on these.......On start up the oil should show signs of returning to the tank quite quickly........20 to 30 seconds max.......When you hear of this time taking too long, it is because of a lack of oil in the bottom of the case, where the scavenge pump has nothing yet to return........not ideal at all......The oil does not get hot as there is no pressure, plus the volume of oil and air flow around the tank contribute to this as well........This is the main reason why the oil tanks get sludge build up.......the lack of heat cannot dissipate any water built up, and the tank does not readily vent it.......another reason why the main tank vent at the rear (T29 fitting) should be left open and vented to the rear axle area.......
I rigged up a small tank with a ball valve, hose and fitting that goes into where the oil jet is. The tank has a schrader valve and is charged with a bit of air. It can also be used for filling the crank etc. You can buy them, but I had the bits in my “someday I’ll use that” bin. Plus I now have my treadmill/paddock starter. Still can’t believe the thing actually works.
As Greg points out, the delay of oil appearing at the filler neck on start-up is dependent upon the amount of oil in the small scavenge chamber behind the flywheels. So it is beneficial to have enough oil in the sump to allow the flywheels to scoop up some oil and drag it to the scavenge chamber. You can overfill the sump for a few turns of the flywheel and then drain the new oil out of the sump and pour it into the tank.
On the Comet racers, I install a new drain plug for the scavenge champer so I can drain all the oil, as well as squirt some oil into the chamber on the first start.
The flange drain plug is the new drain.
From the inside, the drain on the left is the sump drain and the drain on the right is the new scavenge drain.
I did this because I had some problems with removing contaminated oil from the engine. I had some bad oil in the engine and I could not get it out without having to split the cases. This would be unusual on a stock bike, but having done the mod to drain the oil, it was easy to tilt the bike and squirt some fresh oil in the chamber for priming.
David
On the Comet racers, I install a new drain plug for the scavenge champer so I can drain all the oil, as well as squirt some oil into the chamber on the first start.
The flange drain plug is the new drain.
From the inside, the drain on the left is the sump drain and the drain on the right is the new scavenge drain.
I did this because I had some problems with removing contaminated oil from the engine. I had some bad oil in the engine and I could not get it out without having to split the cases. This would be unusual on a stock bike, but having done the mod to drain the oil, it was easy to tilt the bike and squirt some fresh oil in the chamber for priming.
David
Ran my first tests the other day. The results are quite similar to the numbers Dan posted. I mounted the oil tank above the pump to eliminate the possibility of suction head skewing the numbers. I used a litre of straight 30w and measured the time it took for the pump to transfer the entire litre (after the pump was properly primed).It was difficult to get the auxiliary DC motor set to run at a constant RPM, which in turn made it difficult to accurately start the test. The pump was run at 364 RPM (using the lathe motor) which equates to 5,460 engine RPM assuming the ratio of 15 crank rotations to 1 pump rotation is accurate. What was most interesting was the pump’s tendency to suck in air. When I made the test housing for the pump, the bore was drilled undersize and then carefully enlarged to the correct size with a boring bar. When the pump was pushed into the housing (as an assembly) the trapped air would force the rotor back out like an air spring. That told me that the pump is a reasonably good fit in the bore. For the outlet, I used clear hose so any air in the oil was visible. To help eliminate the air, I used sealant between the bronze sleeve and the aluminum housing. Connectors were sealed either with Teflon tape or Loctite thread sealant.
So… Greg’s comment about carefully using sealant when installing the pump is noteworthy. Not so much about preventing oil pressure from escaping, but to prevent the pump from drawing in air. The amount of air would likely increase with engine temperature and RPM. It would also increase if at any time there was positive crankcase pressure which tells me about the importance of crankcase breathing. Another reason to consider adding a reed valve. You’re welcome to draw your own conclusions on that one. There isn’t a lot of real estate between the drive gear and the intake port on the pump, so sealing that area should definitely help, especially if the bore is knackered.
I’ll run another test or 2, verify the crank/ pump ratio and post the results.
Hose clamps were added prior to the test.
So… Greg’s comment about carefully using sealant when installing the pump is noteworthy. Not so much about preventing oil pressure from escaping, but to prevent the pump from drawing in air. The amount of air would likely increase with engine temperature and RPM. It would also increase if at any time there was positive crankcase pressure which tells me about the importance of crankcase breathing. Another reason to consider adding a reed valve. You’re welcome to draw your own conclusions on that one. There isn’t a lot of real estate between the drive gear and the intake port on the pump, so sealing that area should definitely help, especially if the bore is knackered.
I’ll run another test or 2, verify the crank/ pump ratio and post the results.
Hose clamps were added prior to the test.
Greg,
Did you calculate the 15 turns or is that written somewhere?
I've just been out to the shed to find a used oil pump so that I could count the number of teeth on the body of an oil pump plunger. There are fifteen. In a worm and worm wheel gear with a single start gear the worm acts as though it has one tooth so Greg is correct that the standard set up has a 15 : 1 ratio. If one has a two start worm then the ratio would be 7.5 : 1
Did you calculate the 15 turns or is that written somewhere?
I've just been out to the shed to find a used oil pump so that I could count the number of teeth on the body of an oil pump plunger. There are fifteen. In a worm and worm wheel gear with a single start gear the worm acts as though it has one tooth so Greg is correct that the standard set up has a 15 : 1 ratio. If one has a two start worm then the ratio would be 7.5 : 1
First 2 tests with a pump RPM of 364 which equals 5,460 engine RPM. It took 2 minutes and 17 seconds to transfer 1 litre which equals 1.205 cc per revolution.
Third test at 222 pump RPM which equals 3330 engine RPM. It took 3 minutes and 45 seconds to transfer the 1 litre.
So… 3:45 equals 3.75 222 x 3.75 = 832.5 revolutions of the pump. 1,000 cc divided by 832.5 = 1.20 cc. per revolution. My Rube Goldberg test rig and the nanosecond to stop the timer probably account for the 0.005 cc difference.
I’d say something about the fact that even on the wrong side of 70, my flow is greater, but my humour isn’t always appreciated.
Third test at 222 pump RPM which equals 3330 engine RPM. It took 3 minutes and 45 seconds to transfer the 1 litre.
So… 3:45 equals 3.75 222 x 3.75 = 832.5 revolutions of the pump. 1,000 cc divided by 832.5 = 1.20 cc. per revolution. My Rube Goldberg test rig and the nanosecond to stop the timer probably account for the 0.005 cc difference.
I’d say something about the fact that even on the wrong side of 70, my flow is greater, but my humour isn’t always appreciated.