Hi guys,

I've recently acquired a Kitfox 4 and I cant get in the air any long than about 30mins without something going wrong. (makes it quite hard to get my tail wheel endorsement when I cant stay in the air long enough) Its a Rotax 582 Grey Head, approx. 350 hours and 15 years old... never been rebuilt.

Also keep in mind I'm in the northern end of Australia and our flying conditions here are very humid and hot (38°C) 400ft MSL (3000ft Density Alt)

1. First flight : the engine would start to drop RPM (500-1000) for no apparent reason at high RPM. Especially after about 15 secs of WOT. High EGT and high Water Temps. I figured it was a fuel issue, cleaned out all the tanks and fuel, changed the coolant to more water based mix and dropped the radiator 3" into the air stream. I also richened up the mixture one clip on the needle.


2. Second flight : This time I had good EGT temps, Coolant Temps are fantastic... but once again... on a go around at WOT... engine uncommanded drop of 500-1000 RPM only for a short time though. This time I think it might be the fuel pump, so I replaced the gaskets, I also worked out my needle setting should be back on the leaner side due to the higher Density altitude (and slightly dark plugs) and put it back to 1 clip leaner setting and also changed the main jet to one size smaller (leaner). I've also pulled the heads off and noticed my pistons are covered in big flaky bits of crud and the rings are stuck. So, I cleaned it and reassemble.

3. Third flight : I work out I shouldn't be taking off with the flaps in the spoiler position, the aircraft leaps into the air and everything is running great and I'm starting to have hope. There is also a noticeable increase in performance, yes it was doing 70kts!!!!.

After about 10 minutes of circling an abandoned airfield the engine starts to (or at least what I think it doing) misfire! Randomly every 1 or 2 seconds you can feel a kick/thud through the airframe, no drop in RPM. My instructor took over and we headed back to the airfield and by the time we had landed it had gone away.

I'm at wits end with this engine... my instructor won't get back in it with me until I get a new engine. Why would it be misfiring? Should I keep trying to extend the life of this thing, or just bin it?

Help.