I am approaching first start of my 912 ULS. The set-up includes a Thermostasis thermostat unit.
A few weeks ago, we added oil and did our first attempt at purging. Actually we did it three times with a “burping” after each one. We were only using a small pancake compressor and couldn’t get the purge pressure above 5 psi and would eventually run out of air supply. However, it wasn’t difficult to get the oil pressure up above 70+ psi on the G3X just hand-turning the prop. After the third attempt, we checked the lifters and found all four were very soft. Decided to pause for thought.
Got back to the project this week-end. Confirmed that the oil tank was full and that there was oil in the radiator. This time we used a larger compressor and we put a small amount of back-pressure on the oil tank cap, which allowed us to keep the system pressure at 8-10 psi. We did two cycles of purge and burp. Once again, it was quite easy to get the pressure up into the yellow arc, this time hitting 80 psi. With relatively gentle turning, I could maintain the pressure at 55-60 psi. I wasn’t out of breath or sweating and I’m no athlete. We did considerably more than 60 turns each purge.
The pressure gradually fell to 14 psi after rotation was stopped. When I was burping the engine, turning the prop slowly and pausing at each compression, it rose back up to about 20 psi.
At the end of all this, two cylinders still had soft lifters on both arms and one other cylinder had one soft lifter. The arms visibly lifted with around 10 psi applied to the pushrod side of the rocker arm, using a tension tester.
It seems odd that it is relatively easy to get the oil pressure readings up into the yellow arc and sustain them there for a few minutes. From reading and You Tube videos, most people are seeing 40-55 psi but with a lot of effort. Despite this, we still have soft lifters.
Are there any other things we should investigate before just following the Rotax first start guidelines and re-checking the lifters after getting the engine temp up to 122 degrees F.?
Many thanks in advance for advice,
Griff
A few weeks ago, we added oil and did our first attempt at purging. Actually we did it three times with a “burping” after each one. We were only using a small pancake compressor and couldn’t get the purge pressure above 5 psi and would eventually run out of air supply. However, it wasn’t difficult to get the oil pressure up above 70+ psi on the G3X just hand-turning the prop. After the third attempt, we checked the lifters and found all four were very soft. Decided to pause for thought.
Got back to the project this week-end. Confirmed that the oil tank was full and that there was oil in the radiator. This time we used a larger compressor and we put a small amount of back-pressure on the oil tank cap, which allowed us to keep the system pressure at 8-10 psi. We did two cycles of purge and burp. Once again, it was quite easy to get the pressure up into the yellow arc, this time hitting 80 psi. With relatively gentle turning, I could maintain the pressure at 55-60 psi. I wasn’t out of breath or sweating and I’m no athlete. We did considerably more than 60 turns each purge.
The pressure gradually fell to 14 psi after rotation was stopped. When I was burping the engine, turning the prop slowly and pausing at each compression, it rose back up to about 20 psi.
At the end of all this, two cylinders still had soft lifters on both arms and one other cylinder had one soft lifter. The arms visibly lifted with around 10 psi applied to the pushrod side of the rocker arm, using a tension tester.
It seems odd that it is relatively easy to get the oil pressure readings up into the yellow arc and sustain them there for a few minutes. From reading and You Tube videos, most people are seeing 40-55 psi but with a lot of effort. Despite this, we still have soft lifters.
Are there any other things we should investigate before just following the Rotax first start guidelines and re-checking the lifters after getting the engine temp up to 122 degrees F.?
Many thanks in advance for advice,
Griff
