Rotax 582 Running Issues... Help

[lburnard]

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.

[SkyPirate]

take the cowl off,..with tail tied..fire it up..have someone spray some WD 40 on the plug lead wires..if its got a dried out plug lead,,it can arch which will make it run rough etc..try to do it at a darker time of day so he will see if the wires are the cause,,he will see sparks jumping from the wire to the metal it's closest to

[Av8r3400]

At 15 years and 350 hours, it is far past the 5 year/300 hour TBO that Rotax has for this motor.

I would be suspect of all of the "soft" parts on the motor, especially in your climate. Crank seals, hoses, carb gaskets, plug wires all would be suspect at this point. With the humidity and lack of run time, I'd also be very concerned about crank and rod bearing corrosion.

Just my opinion...

[JimS]

That old of an engine you could be sucking air through the seals on the crank. Another thing to check would be the pulse line to the fuel pump (and the pump itself). Good luck!

[Olle1975]

Hi!

Which propeller did you use and which pitch do you set?
Very high pitch and high humidity could drop the rpm by 1000-1500 rpm.

Check all fuelfilters. If you have a fuelcounter, check it, there is a filter inside.

Check your fuelpump (underpressure), there is an membrane inside, all wires from and to the fuelpump MUST be leakproof.

My greyhead had a break of 10 years, now it's 15 years old. I revival it last year and checked pistons and rings. The last 25 hrs, it works perfect.

Olaf

[lburnard]

The prop is a 3 blade carbon fibre unit made by Bolly, it's pitched so my static rpm at WOT gives me roughly 6250 rpm. I don't run a fuel pump and the only filter in the system is the gascolator. I only run fresh 91 RON fuel which gets filtered through a chamois first and I always check for particles from the drain. I stick to Rotaxs engine running proceedures before flight, but everything just seems to happen in the air. I tried running the aircraft on the ground at WOT for about 4 minutes for about 5 runs and it seems to run fine.

As for the rpm drop, it only happed on touch and go's, about 50 ft agl, reducing the throttle a little seemed to stop the problem but I can't really say too much about it because as soon as it happened my instructor pulled the throttle to land, not testing how to fix the situation as his knowledge of engine operation isn't that great.

After my last flight I pulled the carbs fully apart and gave them a good clean out, I synced them the best I could at idle and 3000 rpm. The only thing I noticed is one of my set of floats in the carb bowl have lost some of their bouancy. I've yet to replace them.

I'm going to get my tailwheel endorsement and then I'll be able to test her out at my local airfield and see if I can replicate the problems, hopefully all the work I've done so far will fix the issue. If it still plays up and I don't crash into some tiger country I think it will be time for an overhaul.

One other note, it doesn't seem to consume much / if any injection oil and it's all set up correctly. Should there be a filter between the tank and engine, it seems to restrict the flow quite a bit.

[lburnard]

I've managed to strip the windshield and seat out, most of the frame has crumpled under the seat pan, but because the frame has been pulled down and my forward carry through spar is bent I'm not sure what original diamesions are to rebuild the frame and apparently skystar don't / won't release any drawings.

Can anybody help with diamesions of a simular frame? Tonight I will post some more pictures showing damage.