Have you looked at msrfan's Briggs builds? You are geared way to high. Like I said 2"or2 1/2" then you might have to put a bigger sprocket net to it to slow the rpm's down...........Curt
Just got to rebooking and your tensioner is on top that is the power side and will lift it you need to put it on the slack side(bottom side ) then it might hold............Curt
Another build to check out is Excalibur '09 that mMr.B built it has a big Wisconson engine in it... You can see the tension on the bottom.............Curt