Carburettor | G-MLSY

Rotax issue Service Bulletins alerting owners of known issues or defects that need addressing. The first was to replace the carbruettor floats that have been found to be soaking up fuel and sinking. This could cause rough running or even engine failure. I changed these before the first flight to ensure my test pilot wasn’t at risk.

The latest one applies to my engine and relates to a circlip that holds the jet needle in place. The reason stated was ‘Due to deviations in the manufacturing process a partial fracture of the circlip may occur. This fracture might lead to a crack/ total fracture of the circlip which in consequence may lead to a malfunction of the carburettor. Possible effects might be rough engine running or an unusual engine operating behaviour.’ The replacement needed to be done within 25 hours of the notice issue date but in any event no later than 31st July 2020. Replacement circlips and the ‘O’ rings were supplied under warranty from CFS

As the engine is just coming up to 25 hours and with Maypole’s runway waterlogged it was an ideal time to carry out the change.

*The first thing to do is to remove the carburettor tops* which requires the choke spring and …

throttle and choke cables *to be removed*.

The two screws retaining the top are removed…

The needle retaining screw is removed next but Loctite has been applied to the thread so it’s quite tight to remove. Luckily it unscrewed without too much force.

Once the retaining screw is removed the needle can be withdrawn the circlip removed and replaced making sure to note which of the 4 grooves it was located in first!

The ‘O’ ring that stops the needle moving in situ is recessed in the retaining screw and is also replaced.

The needle is reinserted and Loctite 243 is applied to the retaining screw.

and the choke and retaining springs reattached. The last thing to be done is to reconnect the throttle and choke cables.

Overall the process was very straightforward. The first carb took 45 minutes to do but the second was much quicker at 30 minutes. The engine logbook has been updated and the engine will be test run to check for correct operation before the next flight.

Let’s hope there’s not too many more of these mandatory service bulletins affecting my engine!

Music: Lightening Seeds, The Beautiful South, Gerry Rafferty

Feel like I’m going backward as I need to do some remedial work to the water pump and replace the carburettor floats. But I have a few other things that I’ll do today which will get me back on track. I will o order the registration vinyls (that I have left far too late) and I’ll also be fitting the seatbelts.