Hey guys my sons 65 just started bogging down at low speeds. It idols fine and when you hit the power it takes off like a bat out of he*l. I changed the spark plug put new gas with the same mix ratio I have always used 32:1. I took the needle clip down one notch and it seemed to help a little. The bike a good compresion and ran fine two weeks ago. The weather has gotten a little colder from 60 degrees last time we rode to about 40 this weekend. Any tips on what I should start with on trouble shooting?