Leak down test on a hydro tractor

[pfrederi 18,702]

I want to do a leak down test on the Electro 12 I picked up recently. Most of my horses are geared. Third gear set, the brake and you can run a leak down test on the engine without any problem. On the hydro I am not sure of the best way to keep the motor from turning over when i put air pressure in the cylinder. I don't think the hydro pump will provide enough resistance.

Any ideas/ tips on how to keep the engine from turning???

[SousaKerry 503]

other then a pipe wrench on the drive shaft you could take the engine shroud off and wedge a pry bar or large screw driver in the fins of the flywheel.

[shorts 182]

If you fiddle with it you can find TDC exactly and the air should not turn the engine over, but keep your digits an stuff clear just in case. Put a reference mark on the shroud and flywheel and work back and forth spliting the distance before and after tdc until you find the sweet spot, I use only 5 0r 10 lbs of pressure to dial in tdc and then go to 100 psi for the actual test.

[buckrancher 2,694]

use bottom dead center on the power stroke the motor won't turn and the

valves are closed

Brian

[mavfreak 11]

use bottom dead center on the power stroke the motor won't turn and the

valves are closed

Brian

I've done it this way also, until I thought of it that the bottom of your stroke the cylinder has the least a mount of wear, At TDC compression your cylinder has the most wear at the top.

I now use a socket on the flywheel nut works well.

[buckrancher 2,694]

where the rings ride in the cylinder the wear should be the same at the bottom as it is on the top but that's not what your checking with a leak down test

as the rings have a end gap your checking crank seals and valves

a compression test is for piston and rings and valves

you would also have to seal off the crankcase breather a leak down test is for checking crank seals on a 2 stroke engine not for checking a 4 stroke anyway

I don't see what that would gain you over a compression test

Brian

[pfrederi 18,702]

Thank you some good ideas!!

[shorts 182]

the top of the cylinder has more wear due to several things such as less lubrication, all of the oil comes from below the piston rings, more heat and higher pressures from combustion when the piston is at the top of the compression/power stroke and the rings are flexing from the up to down stroke under the higher heat and pressure of compression with less lube to help minimize wear, and then you add the pressure spike from combustion that exceedes 1,000 psi and decreases as the piston is driven down the culinder until it approaches BDC where the exhaust valve starts to open and relieves all pressure so the burned gasses can be pushed out.

the leakdown test shows cylinder condition and wear at TDC while eliminating the effects of carbon buildup in the combustion chamber, the breather needs to be left open so leaking air can escape and not pressurize the crankcase.

[mavfreak 11]

the top of the cylinder has more wear due to several things such as less lubrication, all of the oil comes from below the piston rings, more heat and higher pressures from combustion when the piston is at the top of the compression/power stroke and the rings are flexing from the up to down stroke under the higher heat and pressure of compression with less lube to help minimize wear, and then you add the pressure spike from combustion that exceedes 1,000 psi and decreases as the piston is driven down the culinder until it approaches BDC where the exhaust valve starts to open and relieves all pressure so the burned gasses can be pushed out.

the leakdown test shows cylinder condition and wear at TDC while eliminating the effects of carbon buildup in the combustion chamber, the breather needs to be left open so leaking air can escape and not pressurize the crankcase.

Good description

Thanks Paul

[Coadster32 793]

Interesting information. :thumbs2: