can any one help me im having a hell of a time with my 2.5 sometimes it runs great then 2 minits later it runs like junk also im geting bubbles in my gas line going to my carb and is there any other moters that will replace the 2.5 other than the siro .18 also i tried all the ajustments that i could thik of even went back to facktory settings many times but still get the same problums slugish at first then run ok for a bit the gets hot and shuts down also seems like it not as fast 2 speed also wont kick in thanks