Misfiring Over 3/4 Throttle During Cruise

Hi Karl,

"With my previous prop the RPM never went over about 5100rpm ......."

Do you man this literally?😈

As a starting point, I would check the spark plugs are ok and all gapped correctly and not too much paste on the threads. 

I say this because your issue is with less load than before. 

Murray Parr wrote:

As a starting point, I would check the spark plugs are ok and all gapped correctly and not too much paste on the threads. 

I say this because your issue is with less load than before. 

Thanks Murray, the plugs are 75 hours old and I did indeed gap them correctly, but I didn't however use thermal paste (first time changing plugs on a Rotax and wasn't aware this was a thing), do you think it possible the plugs are cooked? I assume the thermal paste is to dissipate heat into the heads?

Sean Griffin wrote:

Hi Karl,

"With my previous prop the RPM never went over about 5100rpm ......."

Do you man this literally?😈

Yes, as I've explained to you before in the UK we were limited to 4800rpm max continuous and a MTOW of 450kg, we now have a new MTOW limit of 600kgs and new props approved for 5500rpm max continuous, hence my upgrade.

But my post is about a misfire that I need help diagnosing not UK CAA rules.

Sorry Karl, I didnt mean to cover old ground.

On the current matter;

Speculation; You may have a carbon build-up, due to extended operation of the engine below its optimum torque.

If this be the case you most likly have preignition/knock rather than misfire.😈