If your oil has been changed on schedule, the oil "trap" is unlikely to be clogged. On the 240/740's where it is more accessable, you can remove the flame trap, insert a funnel and dump a bottle of GUNK Engine flush through it when you have the plug out during an oil change. It should run right through and out the hole if it's open and it will dissolve the crap if plugged. I haven't done an 850 but I'd think you could do it the same way. As far as removing it goes, there is an internal line that goes down to the oil sump. If you dislodge this line monkeying with the trap, you're looking at dropping the oil pan to get it back.