Help with jetting

[sprtrx300ex]

I put a WB R-4 slip-on and WB power filter on my 400ex. I put in the dyno jet needle and clip on the 4th notch and a dj160 main jet and 3 turns out on the mixture screw. I rode it and it was blurbering in mid range. I put in a 165mj and little difference. I moved the clip down to the 5th notch and it got worse. I moved clip up to the 3rd notch and the skipping and blerbering stopped, which makes me think the needle is in the right spot.

Everything runs right except that it pops on decel. So today we put in a 170mj. no real difference. Then i decided to try the 160 again just to see if for some reason it was too rich. It just popped more.

Do i need to keep going up to a 175mj and see how that runs?
What do you think i need to do?

Please help. I'd like to get it dialed in perfectly as soon as i can. Thanks guys

[AtvMxRider]

Check and make sure you don't have an exhaust leak 1st. If you do it will pop on decel.

[sprtrx300ex]

I did notice a little black power where the head pipe meets the slip on. I then tightened it up. It wasn't a big leak at all tho. I have the clamp as tight as it will go. I didn't notice any blck power since, but it still pops.

Anyone else ?

[sprtrx300ex]

I just got done reading through the dyno jet kit troubleshooting guide and it said that popping is not caused by a lean main jet or needle, but that it is caused by a lean piolet/mixture screw.

So, Should i go up to a 40 or 42 pilot?