Stray current??

This post has been stagnant for a week.

I have nothing constructive to add BUT feel compelled to ask :

                           Are you sure it's not a wild raisin or perhaps a feral sultana ?????😈

After 30 years of riding along in a C172 without incident, my wife refuses to ride in this thing. But her gag gift was a smudge stick to smoke out the bad juju!   Probably as effective as most things I’ve tried.

Latest change is now difficult starting. Usually starts at the 5-6th time of cranking for 10 seconds.  Positions of throttle and starting carb do not seem to matter.  On two separate occasions, I have pulled a spark plug to check for flooding (not) and spark.  With the plug clamped to the intake manifold, the engine started!  Also starts great after the first start of the day.  

I’m not sure of the significance of erratic low trigger coil resistances, but plan to recheck with the capacitor disconnected. The shop I talked to said it would probably take longer than worthwhile for them to fix the problem, and “sometimes better to start over.”  So it may be a decision of replacing engine and wiring vs selling as is!

Thanks for any input.

"Usually starts at the 5-6th time of cranking for 10 seconds."

Not good! Mine starts almost instantaneously. You will likly kill your sprag clutch/starter motor, with that sort of  performance. Is your battery delivering its rated cranking power? I learnt, the hard way, that you should not persist with a poorly performing battery.

"Positions of throttle and starting carb do not seem to matter."

It should ! - Cold starting a 912 ULS requires NO throttle, FULL choke (for  a second or so). Engine start, followed by part choke, rpm increases (if fitted with auto start). Close choke and increase/throttle to 2000-2500 rpm, for warm up. The whole procedure is almost one continuous action.

"So it may be a decision of replacing engine and wiring vs selling as is!"

Assuming reasonable care and regular servicing, as per the Rotax bible, 800 hrs is nothing for a 912 ULS (most will easily exceed 2000 hrs) .

If you like your Rans S7, I would be starting down the replacing wiring option. Start with the most likly offending system(s) and work progressively. Test between each change. Doing it this way will hopefully save time & money AND will result in an electrical system you can have confidence in.😈

Update: Start with simple things!!

Even though the starter seemed to create normal rpm and the load test while cranking dropped from 12.5V to 10.5V,  multiple airport bums questioned my battery.  A simple jump with a booster spun the prop much faster and started immediately!  Makes sense now that the slightly colder weather had negative effect, while lower compression with a spark plug removed had a positive effect on starter rpm.

Lesson learned—it’s worth a battery swap or a boost with any difficult starting.  Now on to the optional radio repair.

Great learning material this was for me. Learnt lots from reading this thread. Thanks to everyone who contributed.