MAGNETIC PLUG

Before making any assessment, of ferrous metal build up,  you should soak the plug/magnet in a solvent that will remove the oil content - petrol, carburettor cleaner, paint thinner, etc

You will likely find that, once the oil has been removed,  the remaining metal particles no longer appear to be so alarming in quantity.

This is a magnet and as such even the smallest particle will stick to it.  The question is what are the size of the particles.  In the gearbox there are a lot of parts that will give up ferrous metal.  Most of this is not an issue.  What you need to check is the size of the largest particles.  Spray the end with some carb cleaner, it will wash off the oils.  Take the mass in your fingers and pull it off the magnet.  If it simply is power that is normal.  You have nothing of concern until you can find a chip of 3 mm in length or more.  Under that is not an issue especially on a new gearbox that has not worn in as yet.  

The primary producer of such particles are the disk springs that keep pressure on the gear to gear dog inside.  As the engine produces a torsional "bounce" that is then absorbed in the disk spring and ramp system it will produce wear.   The magnetic fuzz is the result of such wear. 

Cheers

The picture shows heavy wear on old disk springs from a 912 series gearbox.  The shiny surfaces are a result of springs moving in normal operation.  The wear shown in this example would be excessive .

How does the oil filter look inside? Did you find any debris in there too?

I suggest you check the magnetic plug after another 10 or 15 hours so to get an idea if there (still) is a continuous build up. With no larger chips on the plug (or in the oil filter) there is no need to worry a lot yet. Keep an eye on it.

Hi,

my 912 UL was brandnew in 2020. Now 160h. The first inspection was done at the recomended 25h, by a professional shop. Nothing was found (only minor sludge). The 100h inspection was done by myself - nothing found at the magnetic screw and into the oil filter.I am a lucky man.

Had you done the 25h inspection? If yes, did you find any particles at the magnetic screw and into the oilfilter? Is it your first inspection after installation the engine? I heard from some minor particles after the first inspection at a brand new engine - its logical. Maybe some fine debrits from the manufacturing or minor traces of wear.  So i can agree with the comments above. Also keep an eye on it for the next 10 to 25 h or shorter like Peter recommeded. Yes it is a short period but in your case necessary.

No panic but next inspection must done very early! New oil, new Oilfilter. Inspect the screw and filter thoroughly. If any relevant debrits or particles found at your next inspection, in my opinion, you need professional help. Notice: the magnetic screw only bind ferromagnetic metals, into the oilfilter you can find any kind of particles which can give you more details about the engine.

And last but not least: Which kind of oil do you use? The recomended oil or others? Maybe you know standard oil for automotive is not properly because the oil for your ROTAX is not only for the pistons/crankcase and so on, it's also for the reduction gear so the recommended oil (for engines with internal gear) is necessary.

Personally I have never seen this much debris on the mag plug even after a gearbox rebuild with new spring washers/propshaft/drive dog or an engine rebuild.