[fatbasser]

ive rejetted my bike and under deceleration it constantly backfires, im wondering if this means its running rich or lean thanks.
2003 crf450
185 main
40 pilot
idles fine
800 ft ASL
ported/polished
st.1 hotcam
full yosh sys
twin air filter
10 degrees celcius
clip is on 2nd spot on needle
thanks guys

[Asmith]

Lean on the pilot circuit.

The pilot seems a bit small.

How far out is the fuel screw?

Open the fuel screw 1/8 turn at a time.

If it's over 2 turns go bigger on the pilot.

[fatbasser]

if i go to a bigger pilot the bike doesnt idle properly, and the screw is set to 1 1/2 turns out. is it bad that the bike is back firing or no, will it damage the bike in the long run or can i just leave it alone, and does the back firing mean it is running lean or not.
'
thanks guys
steven

[Asmith]

if i go to a bigger pilot the bike doesnt idle properly, and the screw is set to 1 1/2 turns out. is it bad that the bike is back firing or no, will it damage the bike in the long run or can i just leave it alone, and does the back firing mean it is running lean or not.
'
thanks guys
steven

When you let off on the throttle, (decel) the only circuit in the carb operating is the pilot jet.

If it's popping, then it's lean. Try opening up the fuel screw to see if that makes a difference.

I can't imagine that the bike wouldn't idle with a bigger pilot. Sounds like something else is in play such as a clogged jet.

Most of us X riders are running from 42's on the small side to 48's on the big side. R's usually run much larger jetting due to head and cam design. Your bike is starving for fuel.

What I would do:

Buy a NEW 42 pilot jet. Get rid of the 185 main, way too big unless you are running a JD needle which you aren't. Replace main with a 175. Move needle down one clip to the third slot.

Open fuel screw up to 1 1/2 turns and fine tune from there.

[fatbasser]

hey guys is it nescessary to remove the float bowl to change the pilot or can i squeez it out through the drain plug thanks
steve

[Asmith]

You can get to it thru the 17mm drain plug. Directly forward of the main jet, in a recessed circular casting.

[JAWS]

Be careful with that casting. They have been known to be broken...
Joe