Brief Description: More work on the engine miss - with success.
The rear plug in cylinder 5 looked a little oily so last time I replaced the plug - with no success. This time I checked the lead resistance and it came up to spec (1,000 Ohm / foot) so no fault with the lead. While Mark & Phil were available we started the engine then ran it on just the right mag where it ran poorly. Pulled the lead off the rear plug in #5 and no change in revs so definitely wasn't firing.
So working further back up the system we checked the ignition leads and after quite some thinking and tracking made 2 discoveries. Firstly, the wrong plugs were being fired by each mag on cylinders 2 and 4 (ie the inlet plug was being fired by the exhaust plug mag etc). This won't have mattered much but it was wrong and the original Jabiru factory harness had the leads placed and cable tied this way.
Secondly, both plugs in cylinder 5 were being fired by the left mag, so of course when the right mag only was selected, that cylinder wasn't firing. This may have been my fault as a few of the leads were loose when I unboxed the engine, but after we tracked all the leads according to the manual and corrected them, a number of leads were too short or too long - making me very suspicious that the factory had the leads wrong ....
However, with the correct leads in place, the engine ran very well with only 20 to 30 rpm loss on individual mags - well within the manual specis. So now we have a properly running engine!
Mark & Phil heloing with the ignition lead tracking check.
