ORIGINAL: Rotcivv17
Maybe if you knew that 4-strokes dont behave inverted, you wouldn't have much problems
All my 4-strokes are mounted inverted, including two YS 110's, three YS 63's, one O.S. 120, and one O.S. 91, and I never had a single problem with them.
YS 110 #1 mounted inverted in a WM Spit:
Not a single problem. Can idle at 2000 rpm all day long.
YS 110 #2 mounted inverted in a GSP Spit:
Not a single problem. Can idle at 2000 rpm all day long.
YS 63 #1 mounted inverted in a VQ Zero:
Not a single problem. Can idle all day long.
YS 63 #2 mounted inverted in a Kyosho Zero:
Not a single problem. Can idle all day long.
YS 63 #3 mounted inverted in a Kyosho Corsair:
Not a single problem. Can idle all day long.
O.S. 120 Surpass III mounted inverted in a GSP Hellcat:
Not a single problem. Can idle all day long.
O.S. 91 Surpass II mounted inverted in a Graupner ME109:
Not a single problem. Can idle all day long.
None of the engines above use onboard glow driver. If you can't get your 4-stroke to run inverted, then it's your fault, not the engine's fault.
I have a third YS 110 waiting to be installed into a Hangar 9 Corsair, and guess what, there is a 99.9% chance that it will run and idle great inverted also.