Highest Possible Value of EGT?

What engine are we dealing with? 912ULS or 912iS?

EGT probes are usually 100mm or 3.9 inches for the 912ULS

and

the 912iS

Approx. 50 mm (1.97 in.) from the cylinder head flange i.e. measured from the flat surface

on the cylinder head to encoder axis. It is important that all 4 temperature sensors are

placed at the same distance!

Roger I am using Rotax 912 ULS.

OK now I present you a slightly different scenario with the same engine. Today I aboserved closely egt response during flight. At take off and climb at full throttle 5500 rpm, all egts were in range around 800-850 deg C. During cruise at around 40% throttle 5000 rpm and 8000 ft altitude EGT4 started to increase at the rate of 4 degrees per minute and after 20 mins flight time, EGT4 reached to 900 degree C. During cruise all the rest of the 3 EGTs remained in range 780-800 degree C. 

After flight all egt's were in range at 40% throttle during ground run. Since I cannot run engine for long period on ground so I don't I understand that why such phenomena in occuring during flight at cruise power setting.
What could be the probable causes of the following?

1. Is there any possiblity of exhaust valve damage.

2. If it is bcz of air leak or needle position setting then why there is no effect on EGT2.

3. Is there any possibilty of bad ignition wire of cylinder 4 or spark plug etc. By the way i have performed ignition test A&B and the max rpm drop is only 150 and checcked the spark plugs as well.

I am using Rotax 912 ULS engine.

姓, xìng wang  

I have checked the same flydat with another engine and the result is ok, normal in range.

As you see in my detailed reply to this post my main problem is why do I get EGT4 value beyond limits during cruising when throttle is around 40%...

Is your EGT4 problem solved or still pending?