I had mine mounted inverted... beautiful that way with very little cowl cutting at all.... Ran and started great. The only problem is the stock muffler (lost 2 of them) just won't stay on.... The stress on the threaded "header" snaps them off... some guys have had them even eat out the threads in the head... or in the least, vibrate and unscrew the muffler off...
I switched to a header kit from Central hobbies... About $60 + $20 for the muffler (a Magnum 120 mufffler)
I JB Welded the muffler to end pipe and it worked great! I then attached the muffler/pipe to the underside of the Ultimate...
I did however, just switch to an O.S. 160FX... the YS 120 AC had plenty of butt for aerobatic flight, but wasn't quite enough for a hover or TR...
If you are interested in my header/muffler I'd sell it for $50...
(tho motor is for sale too... $225 or $250 with the pipe in excellent condition)
Originally posted by grind2tenths
Got my Ultimate a couple of weeks ago. Planning on using a YS 120 AC with a 16~8 APC prop. My question is what kind of exhaust set up is everyone using with the YS? Has anyone mounted the engine upside-down instead of on it's side? Give me some feed-back before I start grinding the cowl.