Hi!
I just picked up a used 03 Z400 that I was pretty excited about but it already has problems. The bike will run 100% as long as your going uphill or on level ground. As soon as you go down a steeper hill it will stall almost instantly. If you go down a hill that's not too steep it will run but the exhaust will make popping noises. I'm almost certain the bike is running lean by looking at the plug. I don't want to start adjusting things in the carb because I just don't understand why the bike would run perfect except when going down steeper hills. What can I do to fix this. Does this bike have an air/fuel adjustment because I cannot find it? It has the stock pipe on it and I'm almost certain it has never been rejeted or had the pipe changed. Any ideas would be greatly appreciated because this is driving me nuts.

So far I have completely cleaned the carb, checked the fuel vent line, adjusted idle both ways, filled up the gas tank, checked all vacuum lines, and made sure choke is operating properly.

 

did you check the float ? run some carb cleaner/fuel treatment threw it ...

 

i'd say sticky float too, that's all i can think of

 

water in gas, float level.

 

Hi!
Thanks for the replies. It turned out to be the fuel screw on the carb. Kinda strange but that's what fixed it. It's 3 turns out now and it runs fine. Still if you go up a steep hill and stop at the top and idle a little while, when you try to go again it will sputter some, but besides that it's running better.