[Brice440ex]

I got a 400ex about a week ago I know it's got a hotcam and aftermarket exhaust and it's not running right you wonder if anybody knows what size Jets I should put in it to make it run right. And I'll let you know what it's doing it won't idle good and it's on the top end it keeps it wants to stutter. Any help would be great

 

[Brice440ex]

Oh and it's bored 40 over

 

[SlammedRanger]

Is it bored .040 over? Or is it a 440 kit? Thats two different things. Welcome to the forums!

 

[Brice440ex]

The guy I got it from said it's bored 40 over

 

[SlammedRanger]

If its bored 40 over its not a 440. That would mean it was bore 40 thousandths of an inch. A 440 would be a 89mm bore. From a stock 85mm. In all honestly to properly jet a engine we need to know what has been done to it. Without that were just guessing. We also need to know what size jets are in it. If its .040 over you will want a 42 pilot jet for starters. That will solve start and idle problem. If its a 440 minimum of a 45 pilot jet. Probably a 48. Main jet will be trial and error until you get it stop popping on decel. Drop the needle clip one slot down(closer to the pointed end)

 

[Brice440ex]

The jets that's in it are bigger but I will find out what size it is and get back to you

 

[Brice440ex]

I put the jets in it . It starts better but now it pops and a little fire comes out my pipes when I rev it up. Do I need to go down one more size

 

[SlammedRanger]

Usually popping on rev and flame out is either lean or there is a exhaust leak at the header flange.

 

[Brice440ex]

It's never done it until I change the jets and it's blows a little black smoke out when it pops and fire comes out

 

[SlammedRanger]

Could be rich. What size jets are in it?

 

[Brice440ex]

45 pilot and a 48 main and 2 1/2 turn out on the fuel-air mixture screw

 

[SlammedRanger]

45 pilot and 148 main? If you had a 48 main jet in it and it revs at all i would be shocked. If its a 148 main that is stock size. Did you drop the needle clip?

 

[Brice440ex]

No didn't do anything to the needle it dose have a hot cam in it don't know what stage.

 

[SlammedRanger]

Ok. Again we are just guessing since were not sure if its a 440 or not. But i would say put a 175 main jet in it and drop the needle clip down one slot.