Hi,,,there a couple of things that are NOT in the instruction book,,,and that i had to learn myself...the fuel nipple on the carb. has to be pointing right at the rear mount bolt,,,next...NEVER trust the factory settings....close off the idle needle and put a piece of fuel tubbing on it and blow...with the throttle in the almost closed position..open the needle till you just hear air comming through. when you have this set...open the high speed needle about 1 1/4 turns and this engine will run fine...i have a 80 inch plane with a ST3000 and itll pull till it gets to the moon..LOL...and,,,,,,,,,,it weighs 24 pds with all the crap i have in it....spinning a 16-8 3 blade...i will say this....this engine is an Italy made engine,,,and the new ones,,,,im not impressed....if you look at the heads of the 4500 Italy,,,and the head from 4500 China...there is a big differance...things do change,, and sometimes not for the better....It really shocks me that i didnt see anyone ask what elevation you were at....remember..prop the engine for the place you live....not what the book sais....Better performance...as far as 2 strokes....the old ST's are one hell of an engine...cant beat em'...good luck..i hope this helped...Rod-AKA Cublover