Anyone have any ideas how far to increase the jet size on a 425 magumn. Only changes are freed up exhaust and K&N. Running with the lid on and off the air box, it still seems lean and have already gone up 10 (165).

 

What do you mean by freed up exhaust? when i put in a K&Nn filter i tought i needed to rejet but when i pulled my plug it was still good(brown with a little black)But my 400 when i put on a pipe and uni filter i had to go from a 220 to a 240 to get it right.

 

I cut the factory muffler in the middle and the back. pulled out some of the insides and made it were you can see straight through it, but you can also screw a 1 inch plug in the back of it and redirect the exhaust back out the bottom (still quiet for hunting) With the lid on the air box it runs ok, if you pull off the lid and still have the filter in it, you take off full throttle and about 20 feet it lays down like it is lean. The more jet I ad the better it runs, I just wondered what jet the "Kit" comes with.

 

I dont htink K&Nn makes a kit for the 425 magnum.All you can do is keep jetting up till it starts to cut out the go back a size or 2.Or just leave the lid on the box.