poppin noise when down shifting

[trx400exat05]

Hi All....... just wondering what this loud popping noise when i down shift and let out my clutch... im thinking its the spark arrestor cause my power core 4 pipe doesnt have a screen on the beginning off the cap and the spark arrestor looks like ****... its all black and it kinda looks like sumone cut it where the cap and the end of the pipe begin... and also how much is it usually to get a new spark arrestor if its the problem....thanks Just being safe to let u all know and dont think im a dumb@$$

[ZeroLogic]

my sparks dose dose that to i kinda like it i think its louder then when i give it haft throttle gas sometime

[Sjorge450R]

my supertrapp does that... i think that it is the rpm's bouncing off of the rev limiter. Its almost like a gurgle.

[ZeroLogic]

i kinda like it
cant be bad can it?

[cals400ex]

try turning the fuel screw out 1/4 of a turn.

[2muchquad]

your motor is experiencing a lean condition.thats the "popping" you hear.try going out on your fuel screw to richen it up.start with a half turn out.:)

[300exOH]

Originally posted by 2muchquad
your motor is experiencing a lean condition.thats the "popping" you hear.try going out on your fuel screw to richen it up.start with a half turn out.:)

I agree with ^. If adjusting the fuel screw doesn't take care of it then you may need to go up a size or two on the pilot.

if an exhaust has a leak it will pop also right?:confused:

[300exOH]

Originally posted by Shift_400EX
if an exhaust has a leak it will pop also right?:confused:

Yes. It could leak at the connection between the headpipe and silencer or where it bolts to the head. A leak basically causes a lean condition.

[Sjorge450R]

mine doesnt pop it gurgles like it is under water...what is that from

[99_300ex]

can someone please post a picture of the fuel screw on the 300ex carb please and thanks.

[300exOH]

Originally posted by 99_300ex
can someone please post a picture of the fuel screw on the 300ex carb please and thanks.

This is on a 400ex carb but from the bottom they look similar. It is the brass screw towards the top of the picture. It would be on the bottom of the carb and toward the front of the quad.

[bwamos]

Originally posted by 2muchquad
your motor is experiencing a lean condition.thats the "popping" you hear.try going out on your fuel screw to richen it up.start with a half turn out.:)

Actually the "fuel screw" is an "air screw" on the 400ex and 300ex Keihin carbs. Turning it out will increase the air flow.

[bwamos]

This might help some.

Duncan Racing Jetting Guide for Keihin Carbs (http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml)

[Chino886]

Originally posted by bwamos
This might help some.

Duncan Racing Jetting Guide for Keihin Carbs (http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml)


That was real helpful, I will try that today before I leave for the dunes.

[trx400exat05]

thanks guys, i think my fourwheeler's fuel screw does need messed with cause it does not idle as well when it was stock and me and bro did turn it out a lil and the spark plug was reeddish brown last time i checked it... i looked good to my bro and it was running good soooo yeah i must be the fuel screw or the pilot ..... i was thinking that but i wanted to make sure before i had to unscrew and take off all my plastics and bolts! ill try it

[trx400exat05]

or could it be cause i dont really have a spark arrestor at the end of the cap and my spark arrestor inside my pipe is old or worn out.???