Geico266

Geico266

Well Known Member
Just a warning to those guys getting their engine kits ready. Make sure you read the warning and literature on the proper procedures for starting a Rotax for the 1st time.

1. There is a specific procedure for pressurizing the oil reservoir so oil is forced back into the engine to purge air from the journals and passages. Failure to do this can result in major engine damage by air locking the oil flow. This is rare, but is can and has happened.

2. Make sure you know how to check the oil. There is a specific procedure for checking oil in a Rotax 912S. After the first start procedure, you'll need to remove the oil dip stick cap, turn the prop by hand until you hear a girggling sound, or check the oil after you run the engine. You cannot just check the oil like a Lycasoris. ;)

3. We call it a "choke", but it is actually an "enrichment circuit". The choke will not work with the throttle open, only when it is closed. When the engine is running the choke does not work (very well anyway). It is a safety feature so you can't kill the engine with the choke in the air.

4. It is a real good idea to take a Rotax engine or maintenance course as soon as you can. These engines are great, run hard, dang near bullet proof, but they are different, and take a different set of skills and mind set to keep the working properly.

Have I forgotten anything?

I'm so pumped to get this bird in the air!
 
Geico266 said:
Just a warning to those guys getting their engine kits ready. Make sure you read the warning and literature on the proper procedures for starting a Rotax for the 1st time.

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A couple of comments:

#1 - Yes, before the engine is first run, or any time when air is let into the oil system except for oil changes, you need to pressurize the oil system. There is a good video of this process that's worth watching. The big problem is air getting into the lifters.

#2 - A little history: The dipstick on the 912 series was changed about 5 years ago. The new dipstick has a higher oil range. As long as the oil is in the acceptable range, you can fly. If you check the oil without "burping the baby" and it's within the OK range on the dipstick, then you don't have to rotate the prop - the oil level is only going to come up when you purge what's left in the engine. It is prudent to burp the oil system occasionally to see exactly how much is in there. Also, very important: Never rotate the prop backwards. This will introduce air into the oil system, and then you have to purge it with air pressure - see #1, above.

#3 - Yes, the choke doesn't work with the throttle even cracked a little. Standard procedure for cold start (from memory): Parking brake SET, Master switches IN, Avionics OFF, Throttle CLOSED, Choke OPEN, Prop area CLEAR, Ignition START, Oil Pressure CHECK. Then jockey the throttle open as you close the choke to get 2000 RPM.

#4 - Yes, they're different. Some good, some bad, but different. The most different things are the carb balancing, the dry sump oil system and the coolant system.

There are some good tips on 912 installation in the Power ON articles written by Phil Lockwood. Here's part 1 and part 2 of the install series, and you can search the index of articles in Sport Pilot for more of the "Power ON" articles.

There's also a DVD put out by ASA that features Lockwood and one of his mechanics going over the 912. If you can't get to a class, it's worth watching.

And on the subject of oil, I'm having good luck with the new AeroShell Sport Plus 4 (how's that for a name?) semi-synthetic. It's expensive, but this is the only semi-synthetic available in the US that allows for the use of either mogas or 100LL up to 30% of the time. And DO NOT USE STANDARD AVIATION OR CAR OIL; the gearbox will not like it, and then you will not like what happened to your gearbox.

TODR
 
Geico266 said:
Excellent point! :D
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Although it could make for some strange kind of aircraft "performance art" :eek:

Some more thoughts:

* Have a carb pheumatic balancer at the ready or hooked up. Do the mechanical sync before first start and then do a pneumatic sync as soon as practical. The engine doesn't like running out of sync. If you're in the DFW area, you're welcome to borrow my sync gauges.

* Set your idle at a minimum of 1600, maybe even 1800. The gearbox doesn't like to run below 1600 and will chatter - that's the sound of hours leaving the gearbox TBO.

* Don't worry too much about cooling during extended ground running - the coolant system should keep things under control unless your CHTs start to creep into the yellow.

* I think there is a suggested check of the mag plug at 5 hr? Might be a good time to do a complete oil change and, as always, cut open the filter and look for expensive metal chips.

TODR
 
Speaking of Magnetic plugs. An FYI, remove the magnetic plug on the side of the gearbox BEFORE you install the engine. The sometimes require excessive force to remove and extraction if it won't cooperate. On older engines we had to drill them. Break it loose on the bench were you have access and safety wire back on. NO LOCKTITE. That's what started the problem in the first place. All the new motors we have installed haven't had a problem but check it. extraction after installation on the airframe can be a pain. Also it would be a good idea to remove the drain plug on the sump can and go get new crush/sealing washers (like 20 of them). Most European auto shops will have them (or can get them for you in bulk) or check a hydraulic repair shop. You CANNOT reuse them or they will usually leak and make a mess. Common problems I see working on them....
 
the_other_dougreeves said:
* Set your idle at a minimum of 1600, maybe even 1800. The gearbox doesn't like to run below 1600 and will chatter - that's the sound of hours leaving the gearbox TBO.
Click to expand...

This reminds me of another Rotax tip for engine shut down. The gear box does not like just shutting the mags off at 1,800 RPM. There is a harmonic osculation that is set up between the prop and the drag of the engine -v- gear box. This can cause problems / wear if not done correctly. If you get a violent shake as the prop stops, this is not good.

To minimize this "shut down shake" what I've done in the past is set the engine idle a little on the low side, say 1400 RPM when the throttle is pulled all the way back. Then when I am ready to shut down (I'm idling about 1,800 RPM where it is smooth) I bump the throttle up just a tad more say 2,000 RPM, and pull it all the way back. As the engine slows to 1,400 RPM, I kill one mag. This drags the engine down a little more, then kill the other mag. This all takes place in about 2-3 seconds. If you do this in a smooth sequence the Rotax 912s shuts down with little or no shake.

Don't miss understand Doug's & my statements about the Rotax engine. They are dependable, robust, reliable little power plants. However, there are little things you can do to help them last longer, and with less maintenance.
 
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Jeromiemead said:
Speaking of Magnetic plugs. An FYI, remove the magnetic plug on the side of the gearbox BEFORE you install the engine. The sometimes require excessive force to remove and extraction if it won't cooperate. On older engines we had to drill them. Break it loose on the bench were you have access and safety wire back on. NO LOCKTITE. That's what started the problem in the first place. All the new motors we have installed haven't had a problem but check it. extraction after installation on the airframe can be a pain. Also it would be a good idea to remove the drain plug on the sump can and go get new crush/sealing washers (like 20 of them). Most European auto shops will have them (or can get them for you in bulk) or check a hydraulic repair shop. You CANNOT reuse them or they will usually leak and make a mess. Common problems I see working on them....
Click to expand...

What is the advantage of removing the magnetic plug? I thought it was there to catch ferrous metal. :confused:
 
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Rotax oil purge...

Geico266 said:
Just a warning to those guys getting their engine kits ready. Make sure you read the warning and literature on the proper procedures for starting a Rotax for the 1st time.

1. There is a specific procedure for pressurizing the oil reservoir so oil is forced back into the engine to purge air from the journals and passages. Failure to do this can result in major engine damage by air locking the oil flow. This is rare, but is can and has happened.
Click to expand...

I am trying to get my thoughts and preparations together for 1st engine start and understand from the Rotax Service Instructions and this thread that you need to purge the oil system by pressurizing the oil tank and turning the prop through, until indication of oil pressure. What I don't understand is what constitutes opening of the oil system in the future to require the purge. From looking at the diagrams of the oil system in the service procedure, if you drain the oil tank to change the oil you could introduce air into the suction line, same as undoing the oil cooler connections. So do you need to purge the system after an oil change?

Tony
 
The "first start" seems to be a very stressful thing most people not familiar with dry sump systems (any old 911 owners out their??) The first start is a very easy thing. fill the oil filter best you can, fill the oil lines and the oil cooler best you can. leave the igntion off and pull out the easiest spark plugs to get to and spin the motor by jumping the starter solenoid with a jumper wire (or a screwdriver for you old FORD owners) until you have oil pressure. Don't run the starter more than 30 seconds per shot. wait until the starter is cool to the touch and do it again.

When you change the oil the procedure is very simple. drain the tank, change the filter, fill the tank to the LOW mark and start the engine. Run the motor for a minute, shut it down, burp it and fill it to the full mark. Why fill to the low mark to start?? Most of my customers seem to ALWAYS overfill it and then have to get the excess out, major pain. Also remember it is a dry sump. The motor will run just fine with 50% of the oil missing.

The only time you should have to do the "first start" procedure is if you remove the oil cooler or its lines.

You will also read and here some say that if you rotate the prop backwards it will cause the end of the earth and destruction of your motor....not quite. The oil pump when spun backwards will pump oil backwards sucking it out of the engine. The hydralic lifters will literally collapse and may not expand again. This only occurs when you spin the prop backwards more than one turn or more. Incidently this will happen to ANY engine with hydralic lifters including your car you drive.
 
Jeromiemead said:
The "first start" seems to be a very stressful thing most people not familiar with dry sump systems (any old 911 owners out their??) The first start is a very easy thing. fill the oil filter best you can, fill the oil lines and the oil cooler best you can. leave the igntion off and pull out the easiest spark plugs to get to and spin the motor by jumping the starter solenoid with a jumper wire (or a screwdriver for you old FORD owners) until you have oil pressure. Don't run the starter more than 30 seconds per shot. wait until the starter is cool to the touch and do it again.
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This is not all of the required steps for purging the oil system. I suggest builders refer to the Rotax service instruction.

Tony_T said:
From looking at the diagrams of the oil system in the service procedure, if you drain the oil tank to change the oil you could introduce air into the suction line, same as undoing the oil cooler connections. So do you need to purge the system after an oil change?
Tony
Click to expand...

Follow the oil change procedure in the line maint, manual. The process is written very specifically to prevent injestion of air into the oiling system.
 
Jeromiemead said:
When you change the oil the procedure is very simple. drain the tank, change the filter, fill the tank to the LOW mark and start the engine. Run the motor for a minute, shut it down, burp it and fill it to the full mark. Why fill to the low mark to start?? Most of my customers seem to ALWAYS overfill it and then have to get the excess out, major pain. Also remember it is a dry sump. The motor will run just fine with 50% of the oil missing.
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Yikes!... This leaves out the very most critical step in the oil change and could cost you up to 20 large!

Namely, you have to reprime the system after filling the tank and fitting the new oil filter. The maint. manual specifies at least 20 turns by hand. You can pull a plug from each cylinder to make this easier; spin it over briskly until you get an oil pressure indication. If you're installing a new filter, this can take a while for the filter to fill up. Also you can usually hear the lifters clicking a little bit before you get the oil pressure by doing it this way, that should go away soon as the engine is primed.

Never just fill 'er up and start it without doing this step! That's ok with a normal wet sump engine, but not with the 912. This can cause horrific damage to the valve train.....

LS
 
there is an easy way. If it's a filter and oil only change, no lines broken into, just turn the engine over with mags off until the oil pressure comes up. done that for years and hundreds of hours. If you have a fresh system, no oil in it, take and grab your compressor and high volume air blower, your gonna need it. what you do is install your filter and oil, you want to take the filter off and fill it as far as it will go. I generally take and fill the lines also. Than take the vent from the tank and pull it out and put it in the cabin with you, this is if your doing things by yourself, turn the mags off(seperate switches is a plus in rotax in relation to the start button by the way) inject air into the vent line and turn over the engine and do this until the oil pressure comes up. Now you can ease things and remove a spark plug from each cylender. You will only want to turn the engine over for 20seconds at a time and give it time to cool down, the starter that is. I have done this one a few times and once on my new engine so far, works great and saves your arms. Now when you put the blast of air into the vent, you generally only have to put a shot of air in there and just hold the air gun to seal the pressure in.

If you are chicken to do this procedure than do it the hard way, this way works for me and anybody that wants to use it.
 
slyfox said:
there is an easy way. If it's a filter and oil only change, no lines broken into, just turn the engine over with mags off until the oil pressure comes up. done that for years and hundreds of hours. If you have a fresh system, no oil in it, take and grab your compressor and high volume air blower, your gonna need it. what you do is install your filter and oil, you want to take the filter off and fill it as far as it will go. I generally take and fill the lines also. Than take the vent from the tank and pull it out and put it in the cabin with you, this is if your doing things by yourself, turn the mags off(seperate switches is a plus in rotax in relation to the start button by the way) inject air into the vent line and turn over the engine and do this until the oil pressure comes up. Now you can ease things and remove a spark plug from each cylender. You will only want to turn the engine over for 20seconds at a time and give it time to cool down, the starter that is. I have done this one a few times and once on my new engine so far, works great and saves your arms. Now when you put the blast of air into the vent, you generally only have to put a shot of air in there and just hold the air gun to seal the pressure in.

If you are chicken to do this procedure than do it the hard way, this way works for me and anybody that wants to use it.
Click to expand...

Yes, very good point. the starter can really be your friend here for doing the priming ;).

One thing about this tho if you combine it with pulling a plug from each cylinder. Make sure the mags are grounded before cranking the engine over. If you have the normal keyed ignition (L/R/Start), this will NOT be the case if you use the ignition switch.
Disconnected (and ungrounded) mags (i.e. no grounded spark plug) can blow the ignition boxes when you crank the engine over at starting speeds generated by the starter (and you can approach that rpm spinning by hand too). Those things are 1000 bucks a piece (for about $30 of parts in a block of plastic and epoxy ;)) so you want to avoid nuking these ;).

So in that case, just hook 12V up to the starter externally and keep the ignition off. Or just leave the plugs in..

LS
 
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