The engine is in a Sig Somthin Extra, no its not cowled. As far as a time frame between flights, it doesnt really matter. It could be after 2-4 people fly or it could be a gas and go. the problem is there for the entire rest of the day once it's been ran the first flight. Now I have played with the low and top end and got it to where the transition from low end to high sounds pretty good and I've leaned out the top end till it starts to puke out then back off till it runs real sweet and then back off like anther 1/8 turn from there. Im stumped. I have read that I might need to run the low end all the way in and back out 1 ful turn, run the high end in and back out 2 full turns. This will allow me to have a good starting posistion. But I'd like to know why it's acting like this.