Some how last weekend I lost a screw on the left side of my carb. Temp fix was to put a piece of tape so I could still ride, no dice. The bike ran like crap, wouldn't go over 1/8 throttle. Took the piece of tape off, ran good till I let off the throttle, then it popped and back-fired.
Today, I turned the air-screw out 1/2 to 3/4 turns (that screw is a pain in the butt to get to), It ran better but sputters at 1/2 throttle, so I run it with the air box lid off...now it runs good. Not enough air? I have the 165 main that HMF gave me in, I'm stumped. Should I run it with no lid? I ride in the woods mostly, and it's been quite muddy, guess I should put on a K&N.
Any thoughts and help appreciated![img]i/expressions/face-icon-small-smile.gif[/img]

 

Well... I'm no expert on Z400 carbs but what screw did you loose?? You might be able to pick up a new one at the local hardware store if it's a regular ol screw. Sounds like it's really throwing you for a loop though! Sounds like your idle mixture screw is still there so it must not be that.

 

I went to the dealership, they looked the carb up on the computer, they have no idea what it does!
The guy told me it's a port from when the carb is made and serves no purpose. I put it back together and did a plug chop, electrode is tan, so I guess it's OK...

 

i have a 04 z400 with hmf slip on to. i had to runn a 165 dj jet with 2 2 inch holes in lid to get it to runn right air screw at 3 turns out. it pulls real hard on top end. i also have stock filter.