snopercod
Well Known Member
Over the last few years, my left mag drop has been getting lower and lower during the runup of my Lycoming O-290-D2. The right mag is OK, but the left is now at the 175 RPM limit (Leaning the engine helps.) Both mags have 300 hrs. on them SMOH. I've put it off long enough so yesterday I pulled the mag and removed the cover over the points. The point gap was only ~0.010, much less than the 0.012-0.024 specification. The points weren't pitted or anything, but they had some whitish oxide on them. With my Fluke, I checked the capacitance of the condenser and it was 0.389 uF, which is greater than the 0.3uF limit. I also checked the leakage resistance and it was 5 nS (200 Megohms). That's gotta' be acceptable. Would the small point gap explain the failed mag check, or should I be looking for something else? It seems like in 300 hrs, the phenolic cam follower could have worn, which would account for the sub-normal point gap, right? Not having the e-gap setting tools, I took the mag (and a new set of points) over to the maintenance shop to have them replace the points and set the e-gap. They have the tools over there. I also took a bottle of Tri-Flow, in case the follower felt needs lubrication. The "official" lube is outrageously expensive ($60), and the Tri-Flow is rated up to 475F.
Does anybody have any experience with Bendix mags? I sure could use some guidance to keep me out of trouble. Thanks in advance.
Does anybody have any experience with Bendix mags? I sure could use some guidance to keep me out of trouble. Thanks in advance.