if you are running nitro, you may need a new piston and sleeve after winter running because the cold makes the entire engine colder and tighter, espesially the piston and sleeve. this leads to increased wear and loss of some compression when you try to run again in warm weather. the best solution is to run in the winter and get a new piston/sleeve for the next summer and keep the old one for winter running. i unfortunately had this happen to me and i couldnt figure it out until i read an article that explained it. good luck. what kind of tempurature do you have this time of year in canada?