Jabiru Aircraft & Engines - Light Sport Aircraft
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Technical Tips - Maintenance, Installation & Operation

Service Bulletin - JSB018-1 Engine tuning - Oct. 5, 2007.

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Head Torque

  • Torque heads on new engines at 5, 10, 15 hours and at 25 hours.
  • Tools needed are torque wrench, 1/4 hex driver (long) and 1/2 inch socket.
  • Remove valve cover. Use rag to catch oil that will drip from head.
  • Remove plug (3/16 hex driver) under rocker arm shaft center bolt.
  • Torque head bolts to 24 ft lbs moving in a criss cross pattern around the head.
    Do not loosen bolts first. Just apply 24 ft lbs to the head bolts as they are.
  • 4" long 1/4 hex driver is needed for the head bolt under the plug at the 6 o'clock position.
  • Reinstall plug with Loctite 242. Torque to 8 ft lbs.
  • Reinstall valve cover (Loctite 242) making sure O-ring is seated in groove on head. Repeat with all heads.
  • If torque continues to change after the 10 hour check, investigate whether the heads are receiving enough cooling. Overheated heads will cause head bolt torque to change as the heads expand beyond engineered limits and then contract. Correct the cooling problem ASAP.
  • After the first 25 hours, check torque during routine maintenance.
    Set the torque wrench to 22 ft lbs.
  • Remember to torque the hidden head bolt at the 6 o'clock position located by removing the plug under the rocker block under the valve cover. 4" long hex driver is needed to torque that head bolt.

Valve Adjustment

  • On new engines adjust valves at 5, 10, 15 hours and again at 25 hours.
  • Tools needed include 3/16 hex driver, 9/16 wrench, straight screw driver, feeler gauge.
  • Remove valve cover.
  • Rotate prop until valve is fully depressed. Rotate prop another 360 degrees and check rocker clearance.
  • Adjust rocker clearance to .010 if necessary by loosening 9/16 jam nut and turning adjustment screw.
  • When clearance is set, tighten jam nut & recheck clearance. Repeat with each valve.
  • There should be very little change after the 10 hour check. If valve clearance continues to change after the 10 hour check investigate whether the heads are receiving enough cooling. Overheated heads will cause valve clearance to change as the heads expand beyond engineered limits and then contract.

Rotor Advisory    Back to Top

Builders using early 3300A engines should check for red phenolic rotor caps in their distributors. These red rotors have shown a tendency to loosen and wear prematurely. Replace with black plastic Bosch rotors. Make sure when installing black rotors that they are fully seatedin the groove in the shaft. The fit is very tight and some effort will be needed to get the rotor all the way into place.

Idle Adjustment

The low idle rpm limit is set with a screw on the throttle arm of the Bing Carburetor. Set with the engine warm and adjust screw until idle rpm of 800 is achieved.

Idle mixture (if smooth idle at 800 rpm can not be achieved, idle mixture adjustment is necessary) is adjusted by the idle mixture screw on the bottom of the Bing carburetor. The screw is recessed in the bottom casting. With engine warm, lean (turn clockwise) or richen (turn counter clockwise) until smooth idle is achieved.

To aid in starting and smooth running in very cold weather, richen idle mixture.


Checking engine compression is done two ways. First for a brief but incomplete check of cylinder compression, use an automotive type compression tester, remove one plug from each cylinder, insert tester in one cylinder and turn over with starter. Compression should read above 90 psi with new engines often reading 160 or above. Second, for a better look at cylinder health, use a leakdown tester designed for aircraft. Position the piston at top dead center on the compression stroke, restrain the prop so it will not turn, and apply 80 psi on the input side. Readings above 60 psi on the lower gauge are acceptable. If there is leakage one can often listen to where the air is escaping - from intake or exhaust valve, thru the rings, or head leakage. Finding the source of the leak determines the cause of action from there.

Maintenance | Installation | Operation | 2200 manuals | 3300 manuals | 5100 manuals

Cylinder Head Temp Sender Installation    Back to Top

Clearance can be a problem when trying to install the 12mm CHT probe. Suggestion - Important: Remove the compression washer from the spark plug. Insert the probe ring on the plug. Reinstall the spark plug compression gasket washer. Before installing the plug in the head, we remove about 1/2 inch of the fin that ends at the top of the spark plug hole. (Install the probe on the exhaust side of the head.) A Dremel with a cut off disk works good for this. Smooth off the cut and then install the plug with the sender. Now there is room for the wire to exit the spark plug area and not be in the way when torqueing the top head bolt.

Tachometer Installation

The most common tachometer pickup location is one of the alternator wires. The resulting pulses per rev will be:

  • 2200A engines = 5
  • 3300 engines w/ three phase = 4
  • 3300 engines with single phase = 6

The alternative location is to mount a tachometer sensor in the tachometer post near the flywheel and count the two tabs on the back side of the flywheel. This results in two pulses per rev.

Carburetor Venting

The Bing carburetor is an altitude compensating carburetor which when set for base altitude will take care of the leaning chores automatically. The carburetor accomplishes this by sensing the difference in pressure between the outside air and the engine air. A diaphram moves a jet needle to change the rate of fuel flow as pressures change and a carburetor bowl vent keeps fuel pressure in the bowl in line. Carburetor float bowl must be vented into the incoming air stream. Run a 3/16 ID plastic hose from the carby vent nipple into the airbox on the clean side of the air filter. Recent Jabiru airboxes have a nipple bonded into the airbox. Run the line to that nipple. If using an air cleaner with no carburetor heat, vent the line into the center of the air cleaner & seal with silicon.

Ram Air Duct    Back to Top

  • Rough fit the duct on the bank of heads and cut out a section of the deflector baffle so the duct will fit over the head fins.
  • Locate the duct so that the spark plugs protrude through their holes and are spaced evenly. Some trimming of the cutouts around the valve covers may be necessary. Drill a 1/4 inch hole thru the duct at the point where the most forward and most rear valve cover cap screw contact the duct. It is these two screws that hold the duct in place.
  • Remove the two cap screws and put the duct in place and insert the cap screws into the duct and tighten them down (but not very tight at this stage.
  • Carefully observe the spark plugs. They should protrude through the holes far enough to easily attach the spark plug lead and it's rubber boot. If the plugs do not come out far enough go to #5
  • On the engine center side of the airduct, mark the arch of the cylinder barrels and then trim off some of the duct where it makes contact with the cylinder barrel fins so that when the duct is replaced, it will "lean" in toward the center of the engine. Often trimming off about 1/4 inch will allow enough "lean" to get the spark plugs out of the duct.
  • Rivet the aluminum angle to the duct near the top center right over one of the cylinder barrels. Run the safety wire loop around the barrel and attach the spring to the wire. Run the other end of the spring to the aluminum angle.
  • After trimming the front of the duct to about 1/4 inch back from the cowl opening, bond the rubber gap seal strip to the duct with five minute epoxy, but first, scuff the rubber and the duct surfaces with samdpaper first to ensure a good bond

Single Phase Alternator Wiring

Regulator Wire Wire Size Connect to:
Pale Blue 16 Alternator Wire
Pale Blue 16 Alternator Wire
Black 14 Ground (Battery Terminal Ground is Best)
Red 14 12V Positive -Direct to battery 30 amp fuse
Yellow 16 12V System
Green N/A Not Used

It would be best to keep the red and yellow wires ahead of the firewall. Run individual wires direct to the battery. Ensure the regulator has a good ground with heavy gauge wire. Heavy guage wire will prevent erratic high voltage readings and spikes.

Oil Cooler Installation

Install oil cooler on slanted part of sump. Direct cooling air between cooler and sump fins. Make sure air is forced to exit thru the cooler. Bracket are provided with Jabiru FWF kits or are available from Jabiru USA Flight Center. See photo for installation details. Radiators may be shock mounted to the brackets if desired.

Vacuum Pumps

All Jabiru engines come standard with a mounting pad for Rapco style vacuum pumps. Pumps and vacuum systems are available from many aircraft component suppliers. Be sure to order a CW (clockwise) turning pump.

Maintenance | Installation | Operation | 2200 manuals | 3300 manuals | 5100 manuals

First Start Procedure    Back to Top

  • Fill oil cooler
  • Add 3.5 qt oil to the sump
  • Remove a spark plug from each cylinder to relieve compression
  • Turn engine over with the starter for 30 seconds and see if oil pressure comes up
  • Let starter rest & cool for 5 minutes
  • Repeat step # 4
  • Replace spark plugs, reconnect leads, install ducts, recharge battery if needed
  • Turn on fuel and start engine.
  • 9. Run on ground for 30 minutes at low power setting or taxi around at low power.
  • Monitor temps on all cylinders and shut down if temps get much over 320
  • Shut off engine, inspect for leaks, loose connections, etc
  • Install cowls
  • Inspect airplane and prepare for first flight. Hasta la vista!!

Cold Weather Starting Tips

All engines are harder to start in cold weather and the Jabiru is no exception. Some requirements for consistent cold weather starts:

  • Strong Battery - The Jabiru ignition requires about 300 rpm to produce a good spark. Your battery must be able to deliver enough current to get the job done. We have tried several brands of sealed batteries that even though rated at 235 cranking amps, would not turn the engine fast enough. We strongly recommend the Odyssey Battery with the model PC625 being the smallest one that will do the job. The model PC980 is excellent for the 3300 if you have the room and can handle a few lbs extra weight

  • Oil - In winter time in colder climates switch to the part synthetic AeroShell 15/50 or equivalent. A few owners have tried full synthetic oils but we have no reports as to the long term effects.

  • Carb - Idle rpm must be set at about 800 rpm (set idle rpm on a warm engine). If the idle is set too high, it dramatically reduces the effect of the choke circuit. Choke cable must be installed so that it will open the choke circuit fully. I've seen some installations where the choke would not go on all the way because of some interference or the cable being misadjusted. Idle mixture should be set a bit rich. The idle mixture screw is located in a recess in the bottom of the carby. Turn the screw counter clockwise to richen. Winter idle mix might have to be as much as a full turn richer than the summer setting.

  • Cold Weather Starting procedure
    • Turn master & mags off
    • Close throttle fully
    • Open choke completely
    • Turn prop thru 6-8 blades by hand
    • Turn on master & mags and start

This procedure does several things. It draws raw fuel in to the intake system. The time it takes to get back inside the plane after turning the prop allows the fuel to vaporize in cold intake pipes.

If hard starting persists in cold weather in spite of the four items above being correct - check the gap between ignition module and magnets on the flywheel. Set gap at .010 to .012. Wider gap will decrease strength of spark produced.

Starter. The starter used on earlier engines with the black motor body with gold ends was a 1 kw unit that was marginal in cold weather. Newer engines feature the 1.5 kw Bosch starter that is much better. If you have an old one, consider an upgrade if cold weather starts are a common problem.

Head Cooling    Back to Top

The Jabiru engines are typical of opposed air cooled engines and the theory of cooling the heads is the same one used for years on most all Lycomings, Continentals, and others. It's simple! Air must enter the top of the cowl and be drawn down through the heads, taking heat away from the heads. To make this process work, there must be lower pressure in the bottom cowl than there is in the top cowl, so that high pressure air is drawn in the top and is exhausted out through the lower pressure bottom. It is easy to get high pressure in the top cowl - just provide openings on each side of the prop that match up with Jabiru's RamAir ducts. Keeping the pressure low in the lower cowl, though, can be tricky.

Any opening in the front of the lower cowl will cause the pressure in the lower cowl to increase. That's why openings in the front lower cowl must be kept as small as possible. For the 2200 Jabiru an opening of 1" x 4" placed at the top of the slanted part of the oil sump is enough and should be considered the maximum opening. An opening of this size is often adequate for 3300 installations as well.

High Oil Temps

One common cause for high oil temps especially in a new engine is too much oil in the engine. Be careful to first drain all the inhibiting oil from the crankcase before filling with new oil. Add only two quarts to a 2200 and only three quarts to a 3300. Let the oil level stabilize and then check the dipstick. Try to get the oil level to one half the way between the full and low marks on the stick. If you are right at the full mark, you can expect to see high oil temps at cruise power.

All engines running in cowled airframe installations should have an oil cooler. The standard size is 11" x 4" x 3/4" single pass 5/16 OD tubing. Any cooler with equal or greater capacity should be ok. Remember, it is necessary to get good airflow thru the cooler to actually do any amount of cooling. Just hanging a cooler inside the cowl doesn't do much. Air must be ducted to the cooler and then thru the fins and out the backside. Allowing cooling air to escape will diminish the cooler's effectiveness.

Rough Idle Suggestions

Possible causes of rough idle below 1000 rpm

  • Idle mixture needs adjustment (see above section)
  • Dirty idle mixture adjustment screw - remove screw completely and flush out.
  • Dirt in idle jet. The idle jet passages are very small and difficult to clean. If the problem can be pinned down to the jet, it is often easier to replace the jet with a new one.
  • Bad spark plugs. Often overlooked but a frequent contributor to idle problems. A plug may look good enough but idle problems may go away with the old plug!
  • Cracked Ignition wires - these are a two year or 200 hour replacement item. Watch those on pushers more closely as the UV radiation will speed the deterioration on engines exposed to the sunlight.
  • Incorrect gap from ignition module to flywheel magnets. Set gap at .012.
  • Weak ignition module - unlikely as these seem to either work fine or not work at all - but still a possibility.
  • Distributor caps & rotors - these do get old and are 200 hour or two year replacement items. Replace more frequently inhumid environments.

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Maintenance | Installation | Operation | 2200 manuals | 3300 manuals | 5100 manuals