fuel/air mixture

First... What Glenn said.

Plus as a very basic rule of thumb is you loose 3% of the engine performance for every 1K ft. above sea level and above standard OAT of 59F. If you tweak it for one altitude then fly to another that may set you up for a failure.

There is nothing wrong with temps in the 1400's. I just stated what the average was that I have seen over the last 20+ years. I've seen some in the 1100's and some in the 1500 range. The problem with being too high is if the right set of circumstances happen then before you can blink you'll have messed up your engine. I have seen several with trashed engines and I know Rotax has seen many too. Like I said it's a range not a specific number, but being nice to your engine makes things more reliable and long lasting. I have friends and know of many others with 3K - 4K hours on their engine because they followed the maintenance and didn't abuse or try to tweak every ounce of power to get 1 knt. of speed.

When you look at the manuals make sure you are comparing apples to apples. You have basically three engines. 912UL, 912ULS and the 914.

"I agree with you but why does rotax say 1470 is normal then. That could make the range more like 1300 to 1550 . We can also control the range with mixture"

I'm not saying you can't make adjustments depending on many things, but most don't know how all these things affect the engine and when they make an adjustment things can go very wrong in seconds and you don't want to loose that reliability. There are safe guards built in and if not many of us would be turned into glider pilots.

"I also was told Egt is more an internal temperature of the burning gas, not really affected by air temps once the engine is up to temp?"

Yes and no. Cold dry air makes a leaner mixture vs hot humid air. So if you took an engine to the extreme in the summer that same setting could cause a seizer in the cold winter air. I used to see this all the time in the 2 stroke Ultra Light days. This also depends on where your engine is getting its air. From the outside or 2 K&N air filters mounted on the carbs always getting hot air. 

You have to consider all things that may affect the engine if you make a change and then decide do I want to take a chance of being a glider pilot or just go enjoy a good reliable engine and fly for the next 2K hours and not worry. You can do things to this engine, but have to reconcile with yourself if it's worth chance, money and possible failure.

Rotax has done their homework and millions of run hours in the industry. better to go with them on this and keep that engine reliability.

p.s.

If your wife is flying with you and you crash the cuts and scrapes from the crash may be the least of your worries if she finds out your alterations caused it. LOL :) .

Thanks again for all the posts... I am learning a lot.  I would just like to restate that my only goal is to tune my carbs to help my engine run smooth and get the most life out of the gearbox.  I do have one more question.  My 912 has one needle circlip at the #3 spot and the other needle at the #2 spot.  From what I understand this is somewhat common.  With my needles set at this postion the EGT readings on the left and right side are spot on so this tells me the mixture is pretty close.  Also, my engine runs extremely smooth when above 3K RPM.  However, it still ran a little rough under 3K and I noticed the EGT for the left side was around 180 lower than the right side (only when below 3K rpm).  I used the idle adjustment screw to get both left/right EGT's closer.  I noticed my engine also runs much smoother in the idle circuit range.  I have reasoned that this is OK since the needle is set at a different height so it makes sense that the idle jet would not be set the same either.  Does this sound OK or should I be looking for some other reason my left/right EGT's were 180 degrees different?

Good information but why wouldn't rotax just state to run these engines at 1300 then? SHouldn't we tune it to around the 1470 normal temps if they have tested it to run there? maybe normal at our normal altitude? I am surprised with the rotax history and testing that they arent more specific . I watch mine maybe too much but wouldnt it be safe to shoot for 1400 normal cruise ?

Sorry I cant get my head around not following the manual. What is the reason that 1472 is normal?

You should follow the manual, but there are thousands of different aircraft and just as many different engine setups so there will always be differences in everyone's numbers up to a point. Many readings from the engine are within a range just like our cars, motorcycles and boats. You can't make exact and consistent numbers in all engine setups and the engine doesn't care so long as it's withing its safe parameters. It's just like our lives. Live within our bodies survivable parameters and we live. Over due it and we may parish or like our engine have a short life. We are all different and live differently, but we all have common ground to survive which is no different than our engine. There are many makes and models (aircraft and engine setups)  just like people and even though the numbers are a little different the engine and us survive.

It's a range we stay within just like blood pressure, heart rate, glucose and even our electrolytes, ect.... They all are okay within a certain range and none of us are exactly the same, just like our engines.

You should follow the manual, but there are thousands of different aircraft and just as many different engine setups so there will always be differences in everyone's numbers up to a point. Many readings from the engine are within a range just like our cars, motorcycles and boats. You can't make exact and consistent numbers in all engine setups and the engine doesn't care so long as it's withing its safe parameters. It's just like our lives. Live within our bodies survivable parameters and we live. Over due it and we may parish or like our engine have a short life. We are all different and live differently, but we all have common ground to survive which is no different than our engine. There are many makes and models (aircraft and engine setups)  just like people and even though the numbers are a little different the engine and us survive.

It's a range we stay within just like blood pressure, heart rate, glucose, cholesterol and even our electrolytes, ect.... They all are okay within a certain range and none of us are exactly the same, just like our engines.