[Zakir]

I have a 98 ninja 250r and it cranks but won't turn over and I did the basic test and everything seem to be ok but it won't just turn over. I am getting good compression, air, fuel, and spark is also good and I took the carbs off and try starter fluid directly into the cylinder but still nothing. the way this started was I took it to store and on the way to store it was fine and on the way back I was loosing power bike wasn't going any faster than 40mph even at full throatle. let me know what can I look for next .thank you

thanks for any help or advise