Carb Issue

Know nothing about 914's - suggest you work through Rotax recommended method for initial setting of the carburettors (see below).  From this initial setting, you should be able to make whatever adjustments necessary, to get the engine to idle satisfactorily - then move on to balancing the carburettors for best performance.

Maintenance Manual Line

Chapter 12–20–00 – SCHEDULED MAINTENANCE

Fuel system ...........................................................................................................................................28

The carbs were set and functioning correctly during previous runups with a normal idle speed.

They seem basically identical to the 912 carbs. 

I can only speak from 912ULS experience -

My new engine, with "Soft Start", starts (when cold) almost instantly.

Method;

Choke full on (I use two plastic pegs on the choke button shaft) .

Throttle fully closed (off).

Start - within a second or so, the engine rpm rises to about 2500 rpm.

Choke half off (remove one peg) .

Choke fully off  (may be a further 2 seconds at most)

 Throttle open to maintain 2300 - 2500 rpm for warm up.

I do not run my engine with choke fully or partially engaged, for more than 2-3 seconds in total.

I do not bring my rpm down to 1700 (idle) until doing preflight checks (oil temp 50+C) 

"The carbs were set and functioning correctly during previous runups with a normal idle speed."

Sound like a control cable/rod may be sticking OR choke mechanism not returning - return spring missing?

My 914 behavior is similar except for the high idle. I have to advance the throttle quickly and simultaneously while closing the choke or it dies every time. Check/drain the oil from the turbo if sitting for extended periods and use 100LL also, it’s more stable.

Sam Purpura wrote:

My 914 behavior is similar except for the high idle. I have to advance the throttle quickly and simultaneously while closing the choke or it dies every time. Check/drain the oil from the turbo if sitting for extended periods and use 100LL also, it’s more stable.

Question, how long to you have to run the engine before this works?

I just did a run where I left the choke on, the RPM gradually rose to 3,000

It wasn't until about 4 minutes then I was able to turn the choke off and advance the throttle simultaneously

After that the engine had normal RPMs / behavior