Magnetic Plug 25 vs 100 hr

I think you are misreading the maintenance schedule.  You are meant to check the magnetic plug for the first time at 25 hours, then next at 100 hours and every 100 hours after that.  It does not matter what fuel you are using.

If you are using leaded fuel more than 30% of the time, Rotax recommends you change the oil and filter every 50 hours (not every 25).

Thanks for reply.  I took the Maintenance Course offered by Lockwood and approved by Rotax a couple months ago.  Lockwood was pretty adamant that if you use 100LL you should do 25 hr oil changes.  It protects both the motor and the gearbox from the bad effects of all that lead.  They strongly recommended doing the entire 25 hr oil change procedure (oil, filter, magnetic plug, and cut open filter for inspection).  I just did mine at 25 hr (560 TTSN) and found significant sludge in the bottom of the cannister.  I was only asking if it makes sense to go through all the mess of the magnetic plug removal (minor) and the oil filter can dissection (major mess).

Lockwood has done extensive testing regarding oil change procedures with the use of +30% 100LL AV-gas. Even though it no longer states you need to do 25hr oil changes in the line maintenance manual (now it's 50hrs), it's still very good practice and we also recommend the 25 hr oil change and magnetic plug inspection when operating more than 30% `100LL Av-Gas.

I understand the recommendation for oil and filter change and will continue to do mine at 25hr since 100LL is awful stuff.  But my original question was more on the necessity for cutting open the old filter and pulling the magnetic plug EVERY time?  Since those are metal shavings issues, not related to 100LL, is it acceptable to perhaps do the oil filter dissection every other oil change (ie, every 50 hrs)?  That's still twice as often as the inspections which typically would be done if using MOGAS and doing 100 hr oil changes.

There should be no problem cutting the filer every 50hrs. Lockwood's suggestion is already going against what's stated in the Rotax Line Maintenance manual, so if you start following the instructions in the manual then you cant exactly be wrong. Check the MAG plug at 100hrs as per the Rotax line maintenance manual and cut open the oil filter every 50 hours (if you run 100LL). Inspection of the MAG plug has nothing to do with the type of fuel you use otherwise it would state this in the Rotax Line Maintenace manual.

https://www.rotax-owner.com/en/support-topmenu/engine-manuals#912-series-engines