03 LTZ400 Question- Rich or lean?

[Blown 97 GT]

I just bought a 03 z400, and when i was riding i noticed that to me it seems like it is running a little lean, because when i let off the gas when coasting or coming down a hill in any gear it pops a few times like its sucking to much air or something. Maybe i'm wrong and its too rich but any help would be great! There is no airbox lid but i rigged one out of cardboard to see if it helped but no luck. The guy i bought it from said it had been jetted for the pro circuit t-4 exhaust. Thanks in advance!

[airmobile101]

Yea, take it up a jet or so...

[drzoo2]

Sounds like your pilot is too lean. First thing I would do it find out what the fuel screw is set for. Just so you know. Turn it all the way in until lightly seated counting the turns. Then back out to where it is now.

Add a 1/4 turn and test the bike. Keep adding 1/4 until the popping goes away. If you get much over 3 turns you may need to jump up to a 25 pilot size.


Once it's set make sure it idles fine.

It not likely a main jet because when you close the throttle the main is no longer in the fuel circuit. This is something that should be adjusted first anyway even if your main is wrong. Each circuit plays into the next one starting with the pilot. Then the needle jet, then the main.
z

[Blown 97 GT]

Where is the air screw on these carbs? I am used to 2 strokes i appologize. The idle screw is the black one on the left side but i haven't found the air screw yet to check it.

[knoxville9]

You mean fuel screw? if so its on the inside

[drzoo2]

The fuel screw on the bottom of the carb closest to the motor side. On newer models it's under a brass cap. There is no cap on an '03. Air screws are two stroke only.

Z

[destey]

I have a stock 2003 kfx400 with only airbox lid removed and exhaust gutted. I had to step up to a 32.5 pilot and its still borderline lean.

Im running a 152 main, which isn't right. Not sure if its too lean or rich but it loses power after 3/4 throttle.

This is all with the stock mikuni BSR36 carb

[cataway]

Originally posted by Blown 97 GT
I just bought a 03 z400, and when i was riding i noticed that to me it seems like it is running a little lean, because when i let off the gas when coasting or coming down a hill in any gear it pops a few times like its sucking to much air or something. Maybe i'm wrong and its too rich but any help would be great! There is no airbox lid but i rigged one out of cardboard to see if it helped but no luck. The guy i bought it from said it had been jetted for the pro circuit t-4 exhaust. Thanks in advance!
you say its been jetted , but do you know what jets are in the carb ?

[Blown 97 GT]

No, i have no clue what jets are in it. Havent even pulled the carb off 2 check. Are the jets located in the same spot as any other 4wheeler carb?

[cataway]

yes