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.

[JimS]

I had a similar problem years ago. Take off was strong but about the time you were clearing the trees at the runway end the motor would start to sag. I have a backup electric fuel pump and the first time this happened the first engine failure item is to turn on the fuel pump. Viola, back to full power. Found I could consistently repeat the issue. Always full throttle with a nose high attitude. It would take about 15 seconds and I could watch the EGTs start to climb followed by the RPM sag. I pulled strainer screens, cleaned gascolator, rebuilt the fuel pump, pulled small pieces of rag through all of the gas lines, test flying each time to find the same problem. Finally removed the pulse line from the engine and found that the hose clamp holding it on the nipple coming off the engine had been slightly past the end of the nipple and was closing the diameter of the pulse line down. (Don't we all give those hose clamps just a slight turn at each condition inspection.) ID of the line was down to about 50%. Enough to run the engine at cruise power and even full power for just enough time to cause trouble. The backup electric fuel pump saved me the first time it happened. Of course this was the last thing I checked (when you find a solution it is usually the last thing you check).
Bottom line, watch the EGTs when your engine sags. If they are starting to climb right before, you probably have a fuel delivery issue.
Good Luck!

[Olle1975]

removed the pulse line from the engine

Do you mean the pneumatic wire whitch is mount from the engine to the fuel pump? Sry my english isn't the best.

I don't run a fuel pump

I've never seen a rotax eingine without a fuelpump. I suggest to mount a fuel pump, I think this is the only way to have a constant fuelpressure (must have between 0,2-0,5 bar) to the carbs.
During the start you need much fuel, I don't know if the fuellevel in the wingtanks deliver enough pressure for the fuellevel in the carbs.
It will be an explanation for this.....

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

I tried running the aircraft on the ground at WOT for about 4 minutes for about 5 runs and it seems to run fine

Olaf

[lburnard]

Sorry what I meant to say was, I don't run an electric fuel pump, although I do have one waiting to be installed.

I checked my pulse line, there is nothing visibly wrong with it.

The only other thing I have done to the mikuni fuel pump is change the gaskets and remounted it horizontally as stated from a few different sources.

[Av8r_Sed]

I'd suggest performing a fuel flow test per this FAA Advisory Circular:

http://www.faa.gov/regulations_polic...a/ac90-89a.pdf

Also,

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.

It should be consuming injection oil. Make sure the alignment marks are matched up between the injection pump arm and casting at low throttle. The arm should advance smoothly as the throttle is opened. You should have a filter between the injection oil tank and engine. It should be a stainless steel wire mesh type, not a paper or fiber element. This will prevent the filter blocking off if you get any water in the injection oil system.