New engine install help

I've fitted a few 912 engines and so in answer to your questions:

1. When purging the oil I just trap a medium thickness polythene bag between the pipe and the fitting. That seems to do the job satisfactorily.

2. I don't know what the substance is on the prop flange. If it is on the front face I would clean it off to allow the prop to sit flat on the flange. If it is on the back then I would leave it as this face can suffer from surface corrosion.

3. The engines are run on a test bed at the factory before being shipped, therefore I would not alter any of the carb mixture settings.

Before you start the engine, make sure that you have satisfactory oil pressure and that you have no fuel leaks. Other than that just follow the manual to make sure that you haven't missed anything.

I hope that helps.

Thank you Kevin!  That helps immensely!

Hi Nick,

Its absolutely imperative that you follow the Rotax manual for purging and initial/static carburettor set up.

Purging, from memory;

You will need access to a compressor with an air regulator, an air "gun" with longish nozzle (similar OD to ID of breather hose) and enough hose to reach your engine.

For setting up the engine for purge; the oil return line from the bottom of the crankcase should be disconnected from the tank and allowed to drain into a  clean container (so that you can reuse the oil).

Remove one spark plug from each cylinder.

Make sure you have at least 3 L of oil in the tank.

Plug the open oil return spigot - I used a short length of oil pipe just pushed on (no need to hose clamp) with a small vice grip to clamp the pipe closed.

Holding the gun open (blasting air) turn your regulator down to the Rotax recommended pressure (I use 10 psi).

Push the nozzle of the air gun into your breather hose (its should just stay there) 

Use a piece of wire or zip tie to keep the air gun open. Air will escape around the tank cap - not a problem.

Start rotating prop as per Rotax instructions.

Handy to have a second person watching the oil pressure gauge to report how its rising.

Carburettor Settings;

You will need an Allan key, spanners (I think 10mm x 2 & 8 mm) & a feeler gauge.

Follow Rotax manual

Set cockpit throttle to idle position

With the carb cable adjust about mid point do an initial adjustment by slipping the cable through the throttle arm and clamping (do not overtighten on cable)

The rest is in the Rotax manual.

Take your time, be very precise and you will be surprised how close you can get to balanced carbs for initial start. After first start and final parts of oil purge, do a pneumatic/vacuum balance to fine tune carburettors.

If in doubt get help from Rotax mechanic or experienced friend.

If you don’t have a compressor you can use a foot pump or even a bicycle pump. You don’t need much pressure to force the oil around the circuit. 

You don't need much pressure but you do need  volume at that pressure.

I  doubt that a foot/hand pump could be employed, to deliver sufficient volume, by anything other than a supremely fit athlete, for the time it may take, to ensure that the oil had carried away all trapped air from the oil cooler and internal galleries.

In desperation, a good quality 12 volt air pump may just deliver sufficient volume but then how would you regulate the pressure?