My buddy built his motor up from crank out, got it installed and could barely get the starter to turn it over and it wouldn't start.
After doing MAJOR testing and researching (he's a computer engineer and can actually dump the ECM code into Microsoft Visual Developer and knows all the tables and inputs, so he knows these systems).
Anyway, we tried to start it, no luck, found the cam sensor was 180 deg. out, fixed that and still turned over very hard, noisy like metal and wouldn't start
Well I used to race motorcycles and jet ski's and I thought of an old trick. Just maybe we'll shoot a little, just a little, WD40 into the TB wide open as he cranked it. In my 2-strokes we used it instead of starting fluid with no negative effects on tear down.
Took two little shots and it fired right up, nice and quiet, then started every time after that with no effort on the starter like before...
So what happened..., best I can figure when he tried to start it with the cam sensor out of time, it washed the cylinder walls down and since it's a new motor it had no compression to start.
By spraying some WD into the cylinders, it must have sealed the new rings off enough to start up. I've used oil as this trick to test for bad rings in the past, but the WD fixed what two days of diagnosing couldn't...