Finally decided to run-in the nice NIB YS .63 I picked up from the swapshop a few weeks back. Unboxed it, fitted the muffler and an APC 13x6 prop. Wups! no glowplug included - so I fitted a new OS F plug by hand. Grabbed my tooltray and off to the carport.

Engine mounted on the stand? check!
Fuel tank filled and secured? check!
Glow heat? check!
Starter? check!
Main needle 2.5 turns open? check!
Regulator set? check!

Let's roll!

... and it refused to run! It started and ran raggedly for a second or two then shut off HARD. Refused to do more than pop after that. I tweaked and tweaked until the starter batteries died... no soap.

Recharged the starter, tried again. Still the same behavior. I was starting to think I'd received a lemon engine... grr.

Defeated, I was turning the engine over slowly by hand and glaring at it when I noticed a slight audible 'hiss' when it turned through compression. A leaky check valve, perhaps?

Then I noticed the fuel bubbling aroung the glowplug. You jknow, the one I had hurriedly scewed in with my fingers an hour-and-a-half ago

Arghgghghg.

Pulled the plug, cleaned the seat, reinstalled. With a wrench this time.

VROOM! Fired right up.

I put three 8-oz tanks through it at low-to-mid throttle settings, running nice and rich. No flameouts until the tank was dry.
Fantastic

Tank #4. I fired up, ran it up to WOT and then ... I leaned the main needle a half-turn. The carport filled with nitro smoke, the mosquitos beat a hasty retreat , the RPMs climbed to a scary point.... I pulled the throttle back, richened the needle and ran out the rest of the tank.

Oh Yes. I'm going to be very happy with this motor