Checking Hydraulic Valve Tappets After Oil Purge Procedure

After performing the purging of the oil system, the hydraulic valve tappets need to be checked to make sure they have pumped up with oil. The hydraulic valve tappet is built into the lower portion of the valve rocker arm. To perform the check, the lower spark plugs are removed and the valve cover for the cylinder being tested is removed. The valve cover is held onto the cylinder head by one M6 screw that is removed with a 5 mm hex wrench. A little bit of caution needs to be exercised when removing the valve cover to insure the rubber O ring on the screw comes off with the valve cover. The larger O ring around the perimeter of the valve cover will typically stay in place on the valve cover but sometimes the tiny O ring around the bolt can stick to the cylinder head and later fall off ... so it is important to verify that it is still on the bolt when the valve cover is removed.

The valve cover has a large gasket around the perimeter of the cover and a much smaller O ring on the M6 bolt as can be seen in the photo.


The test consists of pushing on the LOWER portion of the rocker arm to make sure it feels solid and there is only approximately a .020  gap between the rocker arm and valve stem. A hard plastic dead blow hammer was used to push on the lower portion of the rocker arm. Because the purge was done the day prior the first cylinder tested did not pass the test. I figured this was likely because the oil had time to drain away overnight so the valve cover was reinstalled and the propeller was rotated vigorously for a minute … then the valve cover was removed and the test was repeated, this time with success. Pushing on the lower portion of the rocker arm with the dead blow hammer handle just rocked the fuselage and the valve tappets did not collapse.

Using the handle of a plastic dead blow hammer to press on the LOWER portion of the rocker arm to verify the built in lifter is pumped up and can hold pressure.


The same procedure was used on the remaining cylinders and there were no valve tappets that failed the test. After the testing was completed, the hex nuts on the valve covers were torqued to 90 inch pounds.

Torqueing the M6 bolt on the rocker arm cover to 90 inch pounds.

At this point the oil system is ready for an engine start.

Performing Oil Purge Process On The Rotax 912ULS Engine

Prior to starting the Rotax 912ULS engine for the first time or anytime the supply oil line is removed between the oil tank, oil cooler or Rotax 912ULS engine an oil purging procedure MUST to be followed to remove air from the oil system.


The procedure is not complicated, but does require help. In a nut shell, the goal is to pressurize the oil tank to between 6 and 14 psi of pressure and with the sparkplugs removed from the cylinders, spin the propeller as fast as possible by hand for a minute or two allowing the hoses, oil cooler, and internal oil galleries to completely fill with oil until a steady oil pressure is built up.


The setup: To perform the oil purge, the oil return line from the engine is removed from the In port on the oil tank ... and the In port on the oil tank is capped off. The oil return line is to be placed into a container to capture oil … I elected to just use a vinyl hose directly off the fitting on the crankcase to collect the return oil. The oil tank is pressurized via removing the air vent hose and connecting an air hose to the air vent fitting on the oil tank. I made up a small manifold so an air gun could be connected to a pressure gauge via 1/4" tubing. From the manifold to the oil tank 3/8" ID tubing is used.

An air gun connected to a manifold with an air gauge is used to control the amount of pressure applied to the oil tank. A 1/4" ID hose connects the air gun to the manifold and a 3/8" ID hose connects the manifold to the air vent pipe on the oil tank.

As mentioned previously, I elected to connect a vinyl hose directly to the oil return fitting on the bottom of the crankcase instead of dealing with collecting oil dripping out of a hose on the top of the engine. The vinyl hose created a small issue in that it wanted to kink because the muffler is so close to the return oil fitting on the crankcase the vinyl hose needed to make an abrupt bend. To solve that issue, a piece of stiff safety wire was curled up and inserted into the hose to prevent it from kinking.

To collect the oil that will run out of the oil return port on the bottom of the engine during the oil purging process, a vinyl hose was slipped over the fitting. A piece of safety wire was curled up and slid inside the soft vinyl hose to prevent it from kinking at the bend.


With all systems a go, the manifold assembly was connected to the air vent on the oil tank and the regulator on the air compressor was backed down a bit so Mike K. could easily control the air flow to keep a steady 10 psi of pressure applied to the oil tank. Because the oil pressure sending unit was moved from the engine and mounted on the firewall, figured it would be a good idea to first make sure the hose was full of oil … so the fitting was removed from the oil sending unit (I had never tightened it knowing it would be removed for the purge) and while Bernie held the oil sender  line in a rag, the prop was vigorously turned until oil flowed from the hose. This took a little while because there is a restrictor on this oil line at the engine. Once the line was full of oil it was connected to the oil pressure sending unit and the official purge process began. (Note: Builders who do not move the oil pressure sender to the firewall would not need to fuss with this first step).

Mike K. the “pressure man” controlled the air pressure being applied to the oil tank's vent fitting, keeping it around 10 psi during the purging process. During the oil purge process, the oil return hose is removed from the oil tank and the In port on the oil tank is capped off ... which can be seen in this photo as a blue cap on the In port on the oil tank.

Oil running out of the oil return fitting on the bottom of the crankcase was collected in a clean container and poured back into the oil tank through a paint strainer when the purging was completed.


By the time oil began coming out of the oil pressure sender line I was getting a little tired but after connecting the oil line back on the sender unit continued to spin the propeller until oil began flowing out of the oil return port on the bottom of the crankcase. This is when we switched roles and I turned on the Skyview to monitor the oil pressure, Mike began turning the propeller, and Bernie controlled the air pressure applied to the oil tank. After a few moments the oil pressure came right up and Mike had it holding steady at 78 PSI and the pressure would vary depending on how fast or slow Mike turned the propeller. With the oil purge complete. there is one more step that is required before an engine start is attempted and that is involves removing the rocker arm covers and verifying all the hydraulic valve lifters are pumped up … this will be covered in the next post.


This concludes the oil purging process … we return to normal programing.

S-1201 Spinner Instillation Completed

Conceding to the harsh reality the propeller needs to be removed to complete the S-1201 spinner instillation, Bernie was asked to lend me a hand removing the propeller blades so the S-1202 spinner plate and S-1203-1 spinner bulkhead could be removed to install nutplates. Once the parts were removed the nutplates were bent to match the curve of the parts and then held in position with a screw so the holes for the nutplates could be drilled.

Using a screw to hold the nutplate in position on the S-1202 spinner plate, #40 rivet holes are drilled into the spinner plate.

All the rivet holes for the nutplates are drilled to #40 and the nutplates are secured with Clecos.

After drilling all the rivet holes for the nutplates , all the rivet holes for the nutplates needed to be machine countersunk for flush rivets. I decided to leave the nutplates Clecoed in position to help keep the countersink bit from elongating the holes … likely unnecessary because the spinner plate and spinner bulkhead are made from fairly thick material. After the machine countersinking was completed, the nutplates were riveted onto the parts.

All the nutplate rivet holes in both the S-1202 and S-1203-1 require machine countersinking using the countersink cage outfitted with a #40 100 degree countersinking bit.

Using the pneumatic rivet squeezer to rivet the nutplates onto the S-1202 spinner plate using AN426AD3-4 rivets.

Next work item was drilling the nutplate rivet holes for the S-1202B back plates. After drilling, the parts were given a couple of coats of primer and then white paint and left to dry overnight.

Completed gap filler assembly with nutplates installed riveted onto the S-1202 spinner plate.

Installing propeller blades … Act 2 … A Déjà vu moment. Today all the parts that make up the gap fillers were quickly riveted together and then riveted onto the S-1202 spinner plate so it could be installed along with the propeller blades so the oil purge process could be completed while extra help was available. With the aid of Bernie and Mike K. the S-1202 spinner plate,S-1203-1 spinner bulkhead and the propeller hubs and blades were reinstalled. I did not want to hold the guys up so adjusted the propeller pitch later in the evening after the oil purge process was completed ... this will be covered in the next post. While performing the oil purge, the spinner was temporarily held in place with a couple of screws so the pitot tube could be protected from being inadvertently snagged while hand spinning the propeller.


Upon completion of the oil purge process the spinner was removed so the propeller pitch could be adjusted and bolts set to final torque. Once again the digital level was used to adjust the pitch of the propeller blades to 71.4 degrees which should be a good starting point for doing engine ground run-ups. The process begins by using a couple of equally thick blocks placed on the prop hub so the propeller blades can be leveled.

Because the center of the prop hub is rounded, two blocks of equal thickness are used to elevate the digital level so the roundness of the hub does not affect the level's reading when adjusting the blades to level.


Now that the propeller is leveled horizontally, the digital level is moved to the canopy rail and zeroed. Once zeroed on the canopy rail, the digital level is attached to the Van's prop adjusting tool (TOOL-00002) and placed on the propeller blade. (Because my digital level has a threaded mount for tripod use I drilled a hole in the adjustment tool and attached the tool to the level with a screw because I do not trust the magnets on the bottom of the level). The reason for zeroing the digital level on the canopy rail is it makes the canopy rail the reference point for the prop angle adjustment … so no matter what angle the airplane is sitting at, by zeroing out the digital level on the canopy rail it takes uneven ground or hangar floors out of the equation.

The digital level is zeroed to the angle of the canopy rail by pressing the bevel button then moved to the propeller blade being adjusted to acquire the 71.4° pitch angle.


Return from the future: One of the perks of sharing the building process of the Van’s RV-12 via the DOG Aviation Blog is the feedback received from around the world. After posting the photo below covering the process of using a digital level to set the pitch of the propeller, I received an Email from Nick a fellow RV-12 builder in Colorado saying one of us pitched the propeller wrong and would be saying “crap” …. well, that would be me …. Crap!


Nick referenced a photo on a page in the latest version of the plans that is not in my plans. I had looked at the new version online and it seemed simple enough, but I managed to mess it up by rotating the prop the wrong way to obtain the required 71.4 degrees. I would have had the first RV-12 in the fleet that could back into a hangar under its own power. Thanks Nick for the sharp eye and taking the time to write and get me pitched in the right direction.

Note: The above photo is incorrect ... the level should be leaning to the left and NOT the right. Leaving the photo on the Blog to show readers what NOT TO DO! Using the Van’s TOOL-00002 which was modified so a bolt could be used to attach the tool to the digital level. The propeller pitch is to be adjusted to 71.4 degrees after placing the digital level on the canopy deck and zeroing the level to the canopy deck.

This is the correct orientation for the digital level when setting the propeller blade pitch to 71.4 degrees using the Van's provided TOOL-00002 pitch tool.

Another perk of having the level orientated correctly is it will stay on the propeller on its own without needing a constant hand on it while obtaining the desired 71.4 degrees..


Once the propeller blade pitch was adjusted to 71.4 degrees, the bolts were snugged up and torqued in three stages of increasing torque to a final torque of 19 foot pounds. After the hardware was torqued, the S-1201 spinner was screwed in place.

Torqueing the propeller bolts to a final torque of 19 foot pounds.

Tightening one of the 18 Philips head screws that secures the spinner to the Rotax engine.

Finally a completed task … the Eagle now has a means of propulsion.

Instillation Of The S-1201 Spinner Begins

The euphoria of thinking the propeller installation was complete and good to go was short lived … while reading ahead in the plans, discovered the propeller needs to be removed to complete the spinner instillation. I tried to work around the issue and made great progress … that is until it got time to drill rivet holes for the nutplates on the S-1203-1 spinner bulkhead flange. The angle drill would not clear the spacers under the S-1203-1 bulkhead … so sadly, the propeller blades must come off.


The process of installing the spinner begins with placing tape around the propeller to protect the finish and then placing the spinner in position. It was necessary to do a few on/off cycles for  minor sanding on the S-1201 spinner to clear the propeller blades.

Test fitting the S-1201 spinner after wrapping tape around the propeller to protect the finish.

The spinner alignment begins by making a sighting tool to place in front of the pitot tube to aid in centering the spinner. The camera tripod was enlisted for the job and a ruler was clamped onto the tripod as a sighting aid.

A camera tripod with a ruler clamped onto it is used as a sighting tool to detect the wobble of the pitot tube.

The alignment procedure begins by removing the lower spark plugs so the propeller can be turned easily. The goal is to center the spinner so the pitot tube does not move when the propeller rotates. (The propeller needs to be moved carefully so the airplane does not move … although it will sway on the tires a little but settles when hands are off the propeller blades). I used only two Cleco clamps to begin with one on the top of the spinner and one at the bottom and zeroed the horizontal axis. Next the propeller was turned 90 degrees and the process was repeated ...  when it was perfect, additional Cleco clamps were installed all the way around the spinner to hold it in position for the drilling process.

Sight once the S-1201 spinner was adjusted to center. Placing the propeller in any position resulted in this sight picture after the spinner was completely centered.

Use of Cleco clamps worked out quite well to hold the S-1201 spinner centered for drilling.

The four holes in the S-1203-1 spinner bulkhead are drilled first to #30 and secured with Clecos. After every hole the centering was checked and fortunately the spinner did not move. With the spinner now locked in place with four Clecos in the S-1203-1 bulkhead, the S-1202 spinner plate is drilled beginning with the center holes and working towards the propeller blade cutouts.

All the holes are drilled into the S-1201 spinner … (well almost).

After all the drilling was completed, fortunately the sight gauge was still centered after rotating the prop.

Fellow builders please note: The following photos are not typical in that the propeller was still installed because it appeared a possibility all the work could be done without removing the propeller … but that IS NOT the case, the blades do need to come off to complete all the necessary steps for the spinner instillation ... as I later found out.


Next on the agenda is making gap fillers to cover the slots made for the propeller blades. The two S-1202C gap fillers are made from the scraps that were saved when cutting the blade slots in the spinner. There is a template in the plans that gets the gap fillers to the approximate size, but they still required a lot of extra sanding before clearing the root of the propeller blades nicely. Once the fit was acceptable, the S-1202C gap fillers are clamped to the S-1202 spinner plate and drilled.

S-1202C gap filler clamped in position for drilling.

Drilling the S-1202C gap filler to the S-1202 spinner plate using a #40 drill bit.

Completed drilling of S-1202C gap filler to the S-1202 spinner plate.

For the attachment to the spinner itself, four metal tabs are fabricated by placing a curve in a strip of aluminum to match the spinner’s curvature. Once curved, the strip is cut into 1 ¼" squares. … these squares are used to bridge the gap between the gap fillers and the spinner. Nutplates will be used so the gap fillers can be attached to the spinner.  One of the down sides to using the scraps from the cutout is that there is a gap between the parts from the cutting and the edges seem to taper a bit so the edge that is adjacent to the spinner plate needs to be used as the reference point for laying out the rivet holes.

Installing the S-1202B back plates onto the S-1202C gap filler.

The S-1202B back plates will extend beyond the edges of the gap filler and will need to be cut back. I cut the material back slightly more than necessary so if a little more clearance is desired between the gap filler and the propeller it would be easy sanding without getting into metal. A center line is drawn onto the back plates to aid in drilling the spinner into the back plate. Because the propeller blades were still installed at this point, an angle drill was used to drill through the spinner and into the S-1202B back plate … this hole will be for a nutplate installed later.

My fingers are pointing towards the locations where material needs to be removed from the back plates to clear the propeller.

A center line drawn onto the back plate denotes the drill line for the spinner as can be seen in the photo.

An angle drill being tested for clearance and ultimately used to drill through the S-1201 spinner and into the S-1202B back plates ... (this would not be necessary if the blades were removed as they should be at this point).


Once all the drilling for the gap fillers and back plates was completed, the #30 holes in the spinner are enlarged to #19 beginning with the four holes in the S-1203-1 spinner bulkhead. Clecos for #19 holes were used to keep the spinner positioned. Prior to drilling out the #30 holes in the S-1202 spinner plate to #19 the Cleco clamps were installed to prevent movement while the holes were enlarged and screws were inserted … fortunately, there was no movement.

Drilling the #30 holes in the F-1201 spinner and F-1203-1 bulkhead out to #19.

Drilling out all the holes along the F-1202 spinner plate to #19.

I stopped work short of drilling the rivet holes for the nutplates's on the S-1203-1 bulkhead and F-1202 spinner plate  because it was getting late and there was nobody around the airport to lend assistance with removing the propeller blades ... so will tend to that during the next work session so the S-1202 spinner plate and S-1203-1 bulkhead can be removed for countersinking and riveting nutplates onto them.