I'm seeing very little residue in the crankcases of my 4 stroke gassers after three seasons of flying them. Just a very thin film of blowby components adhering to the case walls. I suspect a walbro pump diaphragm would need replacing before enough residue/buildup occurred to cause a pumping problem, but I don't have any practical experience with this setup.
I suppose venting the case from bottom and a pulse line from the top would be the best long term solution.
Last edited by Glowgeek; 12-27-2022 at 05:00 AM.