I have a Bradley (pretty much...no name) walk behind. 32" 10.5hp Briggs. With the airfilter on, it takes close to 30 (yes...THIRTY!) pulls to get it started the first time for the day. After that...it starts pretty much on the first/second pull the rest of the day. With the air filter OFF, it starts within 3 pulls, and first/second the rest of the day. Why would this be so difficut to pull-start with the air filter on? and by the way, the air filter is 98% clean, pretty much brand new. MAYBE 2 hours on it. What do you think? THANKS!