Goodmorning people....i bought a yzf250 2005 (its my 1st fourstroke)that was sitting for about 6months .the owner told me that cylinder needed to be changed .ok i changed it (but the shop sold me an bigbore athena 83mm by mistake)an serviced the top end and valve adjusted also .cleanded the carb .put on a new spark plug cr9eix iridium ngk .put on a new athena airfilter .now after days of kickik the bike he finally started but stalled right after a few seconds ....now he is starting after a while of kicking (30minutes at most ) then he idles high and stalls again but then still start hard(difficullt).. .what could be the problem?