High EGT

EGT's can be affected by poor connections, poor grounds and a failing probe. Usually I see high and or very erratic temps. It's usually a bad probe. I keep them in stock just because of this.

And of course the fuel mixture influences , but when the EGT temp jumps around like a kangaroo and or goes over the top in temp it isn't the fuel mixture.

Also consider if a wackout temp or pressure is actually true most times it affects other readings and not necessarily just itself. 

Hi Sean

Just switch the probes and you can confirm if it is an engine problem or gauge/probe problem. `In this case you can see the advantage of having 4 EGT.  With only 2 there is no way to determine between the 2 cylinders that carb feeds if you have an actual cylinder problem or fuel flow problem.  if it is fuel flow, ratio, it would be lean on both those cylinders feed by that carb.   Look for an issue within your carb or attachment or even the feed line to that carb side.  A quick look at the mechanical linkage should confirm full travel quickly in the even of a cable slip or linkage issue.  

Cheers

Sean

Check companies like Amazon in your country.  Here is an example of a cheap temp gun.  (must be high temp version for exhaust) 

Always good to do a lot of diagnostics.

Cheers

Hi Roger,

"Also consider if a wackout temp or pressure is actually true most times it affects other readings and not necessarily just itself. "

I do not understand this sentence - please rephrase.

Hi RW,

"Just switch the probes and you can confirm if it is an engine problem or gauge/probe problem."

I will do this however I don't expect to get much information from doing so - remember this EGT spike occurred on the one 60 minute flight so unless the symptoms are a precursor to an unfolding problem, repeat/replication may not happen for another 60 minute flight or longer.

Investigation so far:

Removed newly installed, left rear, modified exhaust header - looks good in/out - re installed.

Removed and tested each EGT probe, using a gas BBQ lighter - both went to 400C immediately - reinstalled. Confirmed spike occurred on left EGT

Did a full carburettor balance - as close to perfect balance/smooth progress, from idle 1800 rpm, through mid range 3000 rpm, to 40000 rpm. repeated several times to be sure.

Thought:

Could there have been a momentary partial/total blockage of carburettor fuel jet, causing a lean condition, within the left combustion chambers ?

Note: I did not notice any change in engine performance/sound.