Rotax 582 engine modifications on CHINOOK + 2
The Rotax 582 engine, gearbox, and prop were purchased used for use on
my Chinook. The engine is a
"gray head" model and had about 650 hours
of use when I bought it.

I knew the previous owner had taken very good care of this engine, and
never had a problem with it other than the oil injection would not pump the
correct mixture to the engine.
He purchased a new pump, new lines, new filters, etc. The injection system
was running at
120:1. Blocking the pump lever full on would only give 70:1
and he and I both carefully checked oil consumption over time, but could get
no better results. We could never solve this problem, and I have since heard
of others that also only use oil at 120:1. Nobody ever checks the oil
but they should.

The oil injection system was removed and mixing at
50:1 has been how the
engine has been run since. At about 650 hours, the previous owner thought
he would give a
Hirth a try, and sold his old gray head engine, gearbox, and
prop to me.

I took the engine apart to be sure it was not damaged and was clean and
assembled correctly before installing it on my Chinook. I now have added
another 550
hours on this engine, and continue to mix at 50:1
Total hours on the engine is now 1200

One modification I made was to increase oil to the crankshaft rear main
bearings. The photos show how this was done with a Dremel type high
speed grinder and carbide burr.

Oil that flows down the hole to the rear bearing, ( or up in my case )
can be restricted by the rubber crankshaft seal. This seal has distance "feet"
that help position it. These feet can really restrict this hole , and I never hear
of re-builders talking about this. To help me position the seal correctly I
place a paint dot on the rear seal to line up with a paint mark where the hole
is. I also modified the hole so oil can blow through to the rear main bearing
more easily.

My 1995 Rotax gray head engine has never had any new parts added other
than gaskets & snap rings. It still has original pistons, rings, seals. I do
decarbon it every 300 hours or so, but this is an easy one day job. Kerosene
and #240 paper to clean the heads. Carburetor soak cleaner for pistons and
rings. Some use of a dental pick is helpful.
I always put the same piston in the same cylinder and have them marked. I
always put the same rings,
with the same face up.
These parts are worn together and you can't get a better fit.
Any ring sticking starts opposite the exhaust ports at the ring gap. Wait too
long and you can't get the rings out of the pistons, then you are looking at
new pistons, honing, boring, etc.
I use Pennzoil Air Cooled.
One of  modifications I made was to remove the set-screw that plugs the
drain hole from the water-pump seal. When the cases are split, you can
see the hole that drains
into a existing slot that is milled between the
case halves.
Heating the screw, allowed me to remove it.

I am told that Rotax plugged this hole because owners would
complain if they saw any antifreeze leaking from joint between the
case halves.
With the hole plugged, any coolant that gets past the seal has no place to
go, but into the rotary valve oil. This is a common problem with the older
582 gray head engine that uses just a lip seal for the water-pump

To also fight this common problem with older gray head engines, I run my
cooling system without any pressure in the system.
This removes
pressure from the lip seal
on the water-pump, and I figure increases
safety as I can never have a cooling system "blow out" such as a blown
hose or seal. I run a 50/50 mix of coolant. Coolant raises the boiling point
of water, and I have no pressure cap. It works like a tea-kettle.
At the altitude I fly at, boiling is no problem. I have never seen any coolant
leaking from the slot shown here. I have never had any sort of overheating
problem, and it uses no coolant.
My Rotax 582 now has 1200 hours on the original pistons and rings and crank.
Maximum revs are loaded to 6250 RPM, however, at 95 mph top speed revs are at
7000 RPM due to prop unloading.

When storing or parking the plane for more that a week, I always position the crankshaft
so both transfer ports are closed to prevent oil fouling the plugs. The crankshaft is
positioned by means of a paint mark on the rubber coupling visible through the hole in the
sides of the gearbox

In the photo at left you can see my over-temp switch in the cylinder head. This switch
was added to one of two holes I drilled and tapped into the cylinder head. The other hole
has a brass plug. ( Maybe a heater someday? )
The over-temp switch is a radiator fan switch from a 1987 Chrysler Lebaron, and it will
light a warning lamp on both panels if temp gets to 190 degrees. It has never lit.
A 1/8
Rotax two stroke engine oil hole shown here.
Crankshaft seal on Rotax 2 cycle engine shows spacer feet.
Dremel Tool or die grinder can be used to improve Rotax oil flow.
Rotax 2 stroke rear seal view shows alignment paint dot for seal
Rotax 582 crankshaft view shows drain for waterpump seal area.
I used a heater core from a school bus for a radiator. It has 5 rows of tubes. This early
photo shows white hoses, but I had trouble keeping the clamps tight, so now I use black
truck heater hose. The radiator is mounted to saddle clamps fitted to the gusset tube, and
has never given a problem. It stays on the plane when engine is removed.
A thermostat is used to keep temperature at a steady 160 degrees. Two 1/8 inch holes
were drilled in this thermostat to allow for filling the system, bleeding air, and keeping the
coolant around the thermostat at a more even temperature and prevent gulping. There is
also an air bleed hose mounted in the existing hole in the water-pump housing that returns
some air and coolant back to my recovery tank.
This photo shows the exhaust system and brackets I made to fit the old "right side up"
Quicksilver exhaust system.
Decarbon using water flow and small piece of wet-or-dry paper.
At 1200 hours, this is how it looks.
Removal of piston rings
Soaking helps remove carbon.
Don't forget the
underside of piston.
Photo used in Pennzoil test. Now called
Heavy carbon below second ring shows
Different oils do make a difference as shown below. Some oils will cause you to
decarbon much more frequently. Some oils combine with lead in gasoline to give much
more carbon. Use unleaded fuel with no additives when you can get it.
If you have had trouble with rapid age cracking of your carburetor socket boots,
CLICK HERE.          
JBM Industries, Kent, Ohio        USA
Questions and answers:
Q:  I read your article on the Rotax 582 engine modifications for the Chinook and found it to be very informational. I have a kitfox with a 582 and ever since I bought it, the oil consumption for
the rotary valve (crank) is more then what the manual calls for. Is this something I should be concerned about? The engine has about 70 hours on since it was rebuilt by a Rotax service center.
There are no signs of oil in the antifreeze or antifreeze in the oil sump. Some of my thoughts are; Would the seal by the rotary valve be leaking and the oil is being sucked into the engine through
the intake ports? Can the oil gravity into the bearings and then thrown onto the cylinder walls? Some one mentioned to me that the seals on the main bearings might be bad, but I don't understand
where the oil would go to if this is the case.

A:  Your concern should be based on the rate of consumption. The space between the cylinders is filled with 2-cycle oil to lubricate the skew gears that drive the water pump and rotary valve
shaft. The method of lubrication is just submersion in oil. ( Keep the gears covered in oil ) Unlike the air cooled Rotax engines, this space is sealed with rubber lip seals, just like the ends of the
crankshaft. Pulse and suction can draw oil past the lips or around the outside of the seal if not installed correctly. Too much oil consumption harms nothing with the engine as it is just burned right
along in the engine. Problems you could have are:
  • Check that your reservoir cap is vented properly. If there is no vent, pressure caused by expansion and heat will force oil past the seals.
  • Be sure the reservoir is not mounted too high, as pressure from the weight of the oil in the hoses will force oil past the seals, more so when sitting motionless in the hanger.
  • Remember if your engine is inverted to switch the oil hoses, as the plastic reservoir has a stand pipe in it to let air escape and make filling easy. This goes to the upper-most case barb.
  • Remember that leakage into the crankcase when shut off for a period of time can cause hard starting and fouled plugs. On inverted engines, place a paint mark on the coupling to the
    gearbox visible through the big hole on each side. Place this mark when both pistons are equal in stroke by checking with a pencil or wooden dowel through the spark plug holes. This
    positions the pistons so the transfer ports are closed and will prevent oil from draining into the cylinders. Turn your prop and position your marks when you store your engine for more than
    a day.
  • Only other possibility is the rubber lip seals are defective, and you will need a new crank to fix that. I always mount the seals with a thin film of Loc-Tite so oil can't get around the seal.

Q:  Hi JBM,
   I really enjoyed your article, but I feel a little stupid. Your labeling of the cylinders and pistons obviously show differences in carbonizing due to the effect of lead from the fuel mixing with the oil
but I feel I'm still missing something. Please explain a little further, was there something other than " watch for, and, or avoid" any  fuel additives? Your indicators do show a gradual increase in
carbonizing but you don't refer to anything that would increase or decrease the amount of carbon build up. Is there something else?   Thanks, Bob

A:  Hi Bob,

 Those pictures of tests were put out by a test on Pennzoil aircooled, vs Pennzoil Outboard, vs Synthetic. I think this test and article can still be viewed, possibly at the Pennzoil or Lockwood
site, but they might have now been taken down, in that Pennzoil Air Cooled is no longer available except in small bottles.
 All the pistons were run equal hours, but the synthetic ( Purple ) was run
at 50:1. I did not write the article or take the pictures.
Note: Pennzoil Air Cooled is now called "Outdoor" oil and is sold in quarts.
  The point I am trying to make is; how much carbon you get varies with the type of oil and fuel, and I put the photos there to show that you will get carbon, and should de-carbon at least every
300 hours. Carbon varies with fuel, and additives can make much more carbon. Leaded fuel like AVIATION Gas, will make much more carbon, as will high test fuel with "injector" cleaners, etc.
refiners think you are putting it in a car.  My point being: de-carbon the thing. It is not difficult to do, and if you keep the parts matched, you will need only gaskets. Waiting too long will
mean rings so stuck, that you cannot get them out, and need new pistons and boring - honing, or you have a seized engine and forced landing.
  Adding oil to gasoline doesn't change its stability. Gasoline-oil mixtures for two-stroke-cycle engines will survive storage as well as gasoline itself.
Fuel stabilizer can harm rubber parts.

Note: The volatility of gasoline is tailored for the range of temperatures expected in the locality where it is sold. Engines fueled with "summer gasoline" may be more difficult to start in cold weather.
Engines run equal hours. Photos taken by Pennzoil.