z400 wont run right

[suzukirider820]

i have a 2005 z400 with some mods. i took it to the shop cause during acceleration it pops. the guys at the shop does not have a clue with whats wrong. he changed the gas, oil, spark plug. he jetted and rebuilt carberator twice, and adjusted the vavules and put in a new rev box. what could be wrong. i would really appericate any help.

[Byte]

What mods have you done to it?

[suzukirider820]

i have a lrd pro 4 series exhaust and a twin air filter and some body work

[jonboy]

What is your jetting and elevation?

[Byte]

Maybe a 25 pilot jet would help. Have you guys gotten into the fuel/air screw under the carb? Check to make sure the head pipe is nice and secure to the cylinder body. When did it start doing this? After the pipe install? Is it hard to start?

[jonboy]

Im just going to throw this out there because I have seen it so many times. But see if the vent on the gas cap is plugged or if the vent hose to the gas cap is plugged. It will cause fuel starvation under acceleration loads.

[suzukirider820]

im not to sure of my elevation but i live in western pa. i have a 147.5 main jet in there. im not sure about my piliot jet. it juste started doing this out of no where but i think it happened not that long after i changed my oil. my gas cap is fine.

[xraven35]

How bout the cam chain? Is your timing off? Make sure your cams are in the right position.

[suzukirider820]

yeah the vavules are fine. but were going ot have the shop look at the timing and all of that. at exactly half throttle it pops during acc. could timing of cam chain be the problem?