Rotax, Rotax 503, Rotax 503 parts.

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Rubber intake socket part number 867-484 
This socket fits the 377/447/503 Rotax engines equipped with the Bing carb. It is a regular maintenance item and should be replaced at the first sign of cracking. 
For longer life, where possible support back of carb(s) and breather. Prior to installation clean socket with acetone, install socket(s) with arrow pointing towards engine, tighten but do not over tighten clamps. Coat exposed area with dielectric grease, this will lubricate socket and help prevent UV deterioration.
Rotax intake socket  377, 447, 503  


#867 484  

Rotax 503 fan belt Rotax engines    

#980 511     

Click here for more information on fan belt, fan belt tools and adjustment.

Mikuni Fuel PumpDual fuel pump 994 485
It is recommended that all Rotax engines use the dual fuel pump supplied by
ROTAX. There is a difference between the pump used in snowmobile/motorcycle/seadoo and aircraft. 
When using the pump on a single carb engine "T" the two lines together. Make sure to isolate the fuel pump from heat and vibration. 
The pulse line should be no longer than 12 inches Pumps should not have to lift fuel any more than 24 inches.

Click here for more information!

Dual Mikuni fuel pump for ultralight aircraft application.  

Rotax aircraft engine parts
PointsPoints - 2 sets required, replace as necessary if found worn, or damaged.
Remember to lubricate phenolic blocks.
Check point gap within 10 hours of new point installation, and ignition timing.

#983 343     

CondenserCondensers - 2 required, replace as necessary if found to be damaged, oil soaked, loose fitting or defective. Threaded #964 219


NGK Spark BR8ES plugs 

The proper spark plug for use in most of the Rotax engines is the NGK B8ES, or other brand name equivalent, (Champion spark plugs are not recommended, nor are they factory authorized for ultralight use.)

If using a spark plug with an BR in its heading, (usually used for ignition noise suppression) such as NGK BR8ES, a resistor cap should not be used. This is because of the double resistance supplied when using both a resistor plug and resistor cap. It is advisable with engines running in the inverted position to use a spark plug with an extended electrode. This aids in stopping spark plug fowling. Look for a BP in its heading (NGK BP 8ES).

When removing or installing the spark plug cap make sure that the cap is turned, in the rotation necessary to tighten the screw on cap on top of the spark plug, otherwise the improper removal of the cap results in the backing off of the screw on cap and the possible loss of spark to the engine, when the spark plug cap falls off. Also see resistor plugs vs. resistor caps!

The recommended gap on the spark plugs is .015 to .019  of an inch. These plugs are capable of running for over 20 hours trouble free on a points and condenser engine and up to 50 hours trouble free on a dual CDI ignition engine (if proper fuel and oil are used and the engine is in proper tune). They should be checked on a regular basis however, and replaced at the first sign of a miss or after severe flooding of the engine.

If using a cylinder head temp gauge, removal of the ring on the bottom of the spark plug is recommended, since the gauge sending unit replaces it. (Cylinder head temperatures should range in the 300 to 400 degree F range.)

In practice, a properly tuned engine should show a nice chocolate, or brown color on the spark plug, white indicates an engine running hot, while black indicates one running to rich. Any sign of aluminum on the spark plug indicates a problem of a very serious nature, and requires your immediate attention!

Electronic box assembly
3-6      966 462

7-9      966 467  






Rotax ignition coil for Rotax aircraft engines
PART #984 555

A regular replacement item.  Suggested replacement every 150 hours, or at the first sign of coil failure. When installing new coils on twin cylinder engines note coils are wired #1 coil is pole 1 to ground while 15 is to points. #2 coil is wired 1 to points and 15 to ground.
When routing ground wire lay it flat against coil so wire does not bend back and forth in the wind-which could cause wire failure and loss of ground.
Also make sure bolts are reinstalled using blue Loctite, or they will come out - these holes use self tapping bolts, without Loctite they will come loose, causing loss of ground, which will result in loss of ignition, or or coil.


Rotax Cageless Bearing

#832 320   

Rotax Circlip   all Rotax 2 stroke

#945 735   

Rotax Wrist Pin   503

#916 186   

Rotax Pistons


503 Standard Rotax Piston with rings


1st over503 Rotax Piston with rings


503 2nd over Rotax Piston with rings


Rotax Rings
503 Top Ring 215 235


503 Bottom Ring 915-850


Rotax Gasket Sets


994-861 Rotax Gasket Set 503 before serial #3786750



994-864 Rotax Gasket Set 503 after serial #3786750


994-236 Rotax 503 Ducati Gasket Set 

Rotax Factory NEW Crankshafts

996-441 Rotax 503 Ducati Crankshaft 



996-471  Rotax 503 Pro 8 Points Crankshaft 



886-445  Rotax 503 Points Crankshaft 



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