Posted Tuesday, January 1, 2013 @ 12:34 PM
We have an RF5B with a L2000, single Slick Mag. The engine has been running for maybe 250 hours using EYQEM A755 plugs. While getting ready for annual, we noticed these plus are badly worn. The ground electrode is at about 50% thickness.
We also have a new set of new BOSCH WB4A plugs. It appears the BOCH are resistor plugs while the EYQEM are not. Looking at old Limbach technical bulletins, I found the following information.
In 1996 TB 51 stated to remove the BOSCH plugs and install EUQUEM at the next spark plug change. The reason was because Limbach was no longer a ditributor of BOSCH plugs. In 2006 Limbach TB 63.2 stated to remove EYQUEM and installl a Limbach PN plug and to change the mag harness to a Limbach PN.
I do belive the mag harness on our engine is a non resistance harness, this would require a resistor type plug. Running the EYQUEM with this harness may explain the worn electrodes. TB 51 made no reference to any required mag harness change.
Right now I think the best thing to do is install the new BOSCH plugs we have on hand. In the future we may have to change to a standard Champion aircraft plug.
Can anyone offer any information or suggestions to this questions on spark plugs?
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Ray Phillips TCSS