fuel/air mixture

This make sense.... but why does Rotax specifiy to set idle adjustment screw to 1.5 turns on both sides when my needle needs to be set at different height on each side.  If I am trying to maximize my engine and gearbox life then it seems I should fine tune by carbs at all RPM's.  Is it logical to fine tune the idle adjustment screw by looking at EGT's on both sides?  By adjusting the idle adjustment screw I can get my EGT's even on both sides if the engine.

You guys are getting to hung-up on specific exact numbers. Think of your engine more like a motorcycle engine and not a Lycombing or Continental. Now think of it as a right and left engine. You have separate carbs, air intakes, two ignition modules, 8 spark plugs, different wear in each carb over time, ect...  What we don't want is the left side trying to run at 5200 rpm and the right side trying to run at 5300 rpm type of scenario. Now they are out of sync and causing vibration you most likely can't feel, but the engine and gearbox can.

Our goal is to have both sides running at the same rpms at all throttle settings. There are reasons your EGT's may not be exactly the same and it isn't just fuel. 

Bill,

I'd put both needle clips in the same position #3. Your EGT's will be different at different throttle settings and that's okay. Unless they are way apart from each other some difference is not a big deal. Trying to do some of the things people post can cause issues under the right circumstances and conditions. We want reliability and longevity out of our engines. Just because some get away with things for a few ours may not play out well in the long run.

Do a carb sync every annual and if you suspect something is wrong in between. Carb syncs are very easy once you understand what the gauges are telling you. With gauges you can diagnose in seconds, but you can't with an electronic device.

Then if you get hung-up on numbers what will you do when the rpms are different during a mag check? It's all okay so long as it falls within Rotax parameters.

I’m 100% in agreement with Roger on this.  Idle screws at 1.5 turns out, needle clips on 3, sync the carbs.  Then, forget about EGT, the engine was not intended to be tuned that way.  And keep in mind that neither the idle screws nor the needle position make any difference once you are at higher power settings (cruise power), where you spend most of your time.   At that point you are running on the main jet, and Rotax is clear in their manuals that any adjustment to the main jet should only be done under their supervision.  The main jet is set by the factory on a test bed at a pressure altitude of 1000’, and the self adjusting nature of these carburetors largely compensates tor altitude changes during flight.  

Just fly safe and often and by doing the right things you can accomplish that for years to come.

I got ya. But does aircraft set up really effect internal combustion temps? ALso can't you change egt with mixture to get to the normal required temperature ? 

I know my engines run pretty close to the same EGT at 90F or 25F but I will test it a bit. So would I be fine to shoot for normal cruise EGT to at 1400 at 3000 msl as long as take off and high altitudes temps also remain in 1472 range?

Here is one more piece to this puzzle. Does spark plug gap affect EGT?