Hi, all --
The following post appeared on another matronics list. Looks
rather useful.
Reg,
Fred F.
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Rotax Discussion
I attended the 7/28/04 8:30am "Rotax 912 and 912S Basic Engine
Maintenance" forum. Here are the notes I took from the session.
Eric Tucker, works for Kodiak Research, the Rotax Importer for the
US. They sell engines to Lockwood Aviation Supply, California Power
Systems etc. Eric was shown as the presenter in the program, but in
fact
he was backup for Phil Lockwood.
Phil Lockwood did most of the presentation. He is the
owner/manager of Lockwood Aviation Supply.
The presentation applied to all Rotax four stroke engines. 912,
912S, 914, certified and non certified versions. I'll use 91x to
indicate
all these engines in the following notes.
Through out the presentation, both Phil and Eric stressed that the
91x family of engines, once running, will get you to your destination.
They may self destruct in the process. Loss of all the coolant will
result in
overheating; engine would keep running, but will likely warp the heads.
They implied the engines would run without oil for a long time - again,
the engine may not restart after this abuse. I believe there were other
examples that I did not write down.
Oil discussion:
- Recommend maximum 50 hour oil change. This is more frequent
than the manual states for some conditions.
- Pre-oil the new oil filter when doing an oil change. (That is
fill the filter with new oil before installing it on the engine. Some
discussion
about mess followed, and Eric said to at least fill the new filter half
way
with oil, then it could be installed without pouring the oil out.)
- When installing the filter, max three quarter turn after rubber
gasket makes contact with the engine case. DO NOT turn filter until
the filter touches the case.
- Oil formulations have been changing during the last several
years. The newer oils foam more. This can cause problems in the
91x family.
- The oil dipstick change was because of the foaming.
- Recommend keeping the oil tank near the top of the range.
- Proper way to check oil is to rotate the prop in the normal
direction until the oil tank gurgles. Then check the level in the tank.
- DO NOT rotate the prop backwards. This can pull oil out of the
engine. A few degrees of backward rotation is not a problem. A full
rotation of the prop could be a problem.
- When changing the oil, just remove the oil tank drain plug to
empty the oil tank and change the oil filter. DO NOT try to get
ALL the oil out. Some customers who have had oil related problems
have rotated the prop backwards to pump the oil out of the engine
during their oil changes.
- Need to use motorcycle type oil because the 91x family shares
the crankcase oil with the gearbox oil - like most motorcycles. This
oil
has additives to protect the gears.
- Castrol GPS and Motul have been REMOVED from the
recommend list because of foaming.
- Penzoil motorcycle oil is OK to use
- Any semi synthetic motorcycle oil is OK to use.
- Honda motorcycle oil will not be listed as OK to use because
Honda is possible competitor, but the Honda motorcycle oil is OK
to use.
- California Power Systems AV-9 showed some foaming in testing
and is currently being reformulated.
- DO NOT use pure synthetic oil when using 100LL fuel. Pure
synthetic will not hold the lead in suspension properly.
Cooling discussion:
- Recommend CHT operation in 180F to 240F range. Also
recommend max of 125C which is higher than 240F.
- It is normal for EGT and CHT to be different on each side.
- No real value to having EGT.
- IF the center of the CHT sensors supplied with the engine are
gone, then the engine has been TOO HOT. The center of the sensor has
melted.
- There is a new higher pressure radiator cap available. Eric did
not seem to enthusiastic about it. Typically raises the temperature
before
releasing pressure about 10C.
- Use phosphate free coolant.
- Use silicate free coolant.
- Dexcool coolant works well.
- Don't mix green and orange coolant. Flush system if changing.
- Recommended minimum of 50% coolant (with remainder being
distilled water).
- If having trouble with coolant/distilled water boiling, may need
to move to highest recommend concentration of coolant as recommended
by coolant manufacture.
- If still having trouble with coolant/distilled water boiling,
using Evans coolant is OK. Evans coolant does not use water and runs
without a pressurized cap.
Fuel:
- If flying over 12,000ft, recommended using avgas to avoid vapor
locking.
Carburetors:
- Keep the carbs synchronized. Check every 100 hours. Check at
idle and just off idle.
- Recommend 1800 rpm as minimum idle speed to maximize gearbox
life.
- Recommend overhauling the carbs every 600 hours.
- Choke (enricher) only works with the throttle fully closed.
- Recommended running 2200-2400 RPM just after start until engine
will idle smoothly below this speed.
Gearbox discussion:
- Recommend 912S engines be upgraded to the slipper clutch. There
is increased possibility of kickback with the slipper clutch.
Therefore, this
also requires the upgraded starter at the same time. There is a reduced
cost
upgrade program available.
- Recommended having gear box serviced every 300 hours of
operation for 912S without the slipper clutch (over run clutch).
- There was a recommendation to check the gearbox play every 100
(?) hours of operation. The discussion followed what is in the manual.
This
is for engines which do not have the slipper clutch. Sorry, I'm not
sure of
the frequency that was recommended.
- Would not try to hand prop a Rotax 912S. Much higher
compression
than the 912 or the 914.
There was a discussion about the service bulletins. Basically,
there are bulletins because the factory continues to develop the
engines.
The development is the result of customer/user feedback. Service
bulletins
are only required for certified versions of the engines in certified
planes. The
service bulletins are a good idea for the non certified engines.
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