Carbie Synchronisation

[Bluey]

Hi, Just did a carbie sync for the first time and was interupted by some weather so couldn't quite finish it. I used the dial system supplied by airborne. Ifound that there was indeed a significant difference between the carbies at around 4500rpm (about 4inches of Hg at this rpm according to the supplied dials, 4 divisions). Anyway , after a small adjustment, I managed to get it very close to balanced. However, at idle there is a difference of about 1 inch of Hg (1 division). Just wondering if it is nescessary to make any adjustment to the idle (which is currently sitting at 1850rpm) if the the carbies are quite close anyway?

 

Bluey

 

 

[facthunter]

Hi, Just did a carbie sync for the first time and was interupted by some weather so couldn't quite finish it. I used the dial system supplied by airborne. Ifound that there was indeed a significant difference between the carbies at around 4500rpm (about 4inches of Hg at this rpm according to the supplied dials, 4 divisions). Anyway , after a small adjustment, I managed to get it very close to balanced. However, at idle there is a difference of about 1 inch of Hg (1 division). Just wondering if it is nescessary to make any adjustment to the idle (which is currently sitting at 1850rpm) if the the carbies are quite close anyway?Bluey

You might as well finish the job. The error you have is small at idle. but it's done on the idle stop screw unless the cable has no free play or movement. You need about 2 mm of slack to ensure that the slides are free to close when the throttle is fully closed at the lever. If they don't work this way the idle will not be consistent. ( I'm presuming that we are talking about the 582 here.).. Nev

 

 

[Bluey]

Thanks for the advice facthunter but the engine is the 912. I will go the extra mile to get the idle balanced as close as possible too.

 

Bluey.

 

 

[Blueadventures]

Hi Bluey

 

A web site that may be of help is lightsport aircraft under a google search for carburettor balancing rotax 912. The people a bert flood are always very helpful.

 

Cheers

 

Mike

 

 

[HEON]

Anyone with a Rotax should look at the USA site Rotax Owner. If you join they have very good vido of numerous maintenance tasks and other services

 

 

[Kev]

Bluey,

 

The short answer is yes. Keeping the carburettors balanced is very important to the smooth running of the engine. It is detailed in the Rotax Line Maintenance Manual Chapter 12-20-00 para 10. It starts with mechanical synchronisation which basically gets you into the ballpark to then carry out the pneumatic synchronisation. Although there is a balance tube which compensates for any minor differences, you should attempt to maintain the balance as well as possible.

 

The balance at idle is very important as any difference here will be a greater percentage. Having the idle set lower than 2000rpm will help reduce the shock loading during start up and shut down of the engine, however when running you should try to keep the idle at not less than 2000rpm. This reduces the stress on the gearbox.

 

The pneumatic synchronisation basically consists of two separate settings - the idle, set on the idle screws, and then the off-idle, which is set on the cable adjusters. It is important that the cables are lubricated regularly and are free moving. If one of the cables drags a little, this will tend to put the balance out throughout the range.

 

Dont forget to use brakes, chocks and tie the aircraft down as you will be checking it right up to max power.

 

Hope this helps.

 

Safe Flying

 

Kev

 

 

[Bluey]

Thanks everyone. I've done the balancing and it does seem to be smoother but the difference is quite subtle. I will make sure to check it according to the manual.

 

Bluey