Just to close the loop on this, it looks like insulating the fuel lines from the spider on top of the engine down to each carb has fixed the problem. I've had half a dozen hot starts since then with no problem at all.
I guess I spoke too soon - I'm still seeing this problem repeatably. It starts fine if I restart right after shutting down, it restarts fine after sitting for 30 - 45 minutes but starts real hard if I try 10 - 15 minutes after shutdown. I say "hard start" but it's actually more of a rough start. The engine runs but is very rough for 30 - 45 seconds then smooths out and runs great. During that rough running period the left EGT comes up pretty much normally but the right EGT doesn't budge. After the 30 - 45 seconds the right EGT comes up and the engine smooths out.
I've put a reflective thermal wrap on the line from the fuel spider to each carb. I've also just finished wrapping the exhaust pipes from the heads to the muffler with thermal wrap. I open the cowling oil access door when I shut down. btw, this in an RV-12 installation.
I'm about out of ideas. Any thoughts would be appreciated.
As a data point: Operating year-round in Northern California weather with Van's standard ROTAX installation, I have not experienced these starting problems. I, and most RV-12 operators I know, make a habit of opening the oil cap access door immediately after landing to allow the upper cowled engine area to cool. Perhaps this may help with your issue?
Thanks David. That was my first try at dealing with the problem. I tried insulating/wrapping once I found that didn't work.
From what I've been able to tell, the problem I'm seeing is rare at best. I've not heard of any other RV-12s that exhibit this particular problem. Not sure why I'm seeing it. I'm assuming vapor lock but don't really know if that's the problem or not.
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