912 ULS rough running at 2350 to 2450 rpm

Hi all.

The engine and carbs has total 450 hours. manufactured in 2017. Airplane Model TL3000 Sirius 450 hours.

Sean the problem was , regarding the rough running, it got much worse AFTER renovating the carbs, so until now i will expect the prop is ok. I have orderd new  engine rubbers as TL Ultralights recomends changing them with intervals. I will change them next week anyway.

 Roger the 1,5 turns are the same on both sides, When installing the vaccum clocks( gauges ) they are equal all the way up through the rpm range. Also equal when the engine runs rough at 2300 to 2650 ish.   During cruise with 4900 rpm. the EGTs are left side 710 degrees celcius, and right side 695 degrees celcius. ( of cause temp. varies with the heigt) BUT in idel the left side is 40 degrees celcius LOWER than right side..... summary It runs smooth in all cruise settings. 

Gudmundur it is an interesting video. I have not found any debrees ( metal) in the oil filter or on the magnetic plug for the last 3 oilchanges ( made every 75 hours). So that will be the absolutly last thing i will try. The slipper torque is also ok .

The spark plugs are equal brown after a cruise tour, but when in idel for 5-10 min. they are more black. Actualy i remember when pulling the choke a little bit out in idel, it runs a little bit better., not so rough.

Summary, i have tried so much different, so next  week i will start again, and write down every step and result, to keep them in order :-)

I still "love " my airplane though :-)

Best regards Allan

Hi Allan,

Nice aircraft.

I expect the replacement of the engine "rubbers" will either fix the problem or at least make it significantly better.

As for propeller balance -

I assume you have checked the propeller blades for tracking and static balance.

Dynamic balance is, in my view, essential for minimising propeller induced vibrations, a static balancing can not take into account the effects of gyroscopic irregularities. These irregularities are likly to be most obvious at certain propeller (engine) speeds.

😈

Allan, a little off topic but don’t worry about black spark plugs after some idling - that’s pretty normal. Brown for cruise is good.

The temp differences in EGT you report do not seem to be too relevant to me keeping in mind that EGT sensors do have some spread in accuracy.

There is some chart on the web that describes the function of the different jets/needles of a Bing carb over revs. Perhaps, particularly because your probs appeared or got worse after carb maintenance, you like to check that charts and the status of the jet that is responsible for the rough RPM band.

Regards

Peter

Hi Allan

As mentioned earlier I was afraid of wear in the gearbox

I removed the gear and took it apart, There was a wear in the dog gear

one more I got an other gear and now the engine run fine in all rpm.

Best Regard

Gudmundur