I have a Redmax 8000 backpack, I put a new top end in it back at the beginning of the summer but havent had a problem until a few weeks ago. The blower is hard to start when cold, first start up of the day. After that it starts no problem. I have replaced the spark plug but that didnt work. I dont think the new top end has anything to do with it because the problem only just started happening. Airfilter is clean. Only thing I can think of is a carb issue but what could it be?