Barely any pressure out of one pipe.

[coleman66six]

Brand new rebuild and now only one pipe actually “pushes” smoke and the other has barely any pressure coming out of it that I can feel left pipe seems to smoke and has plenty pressure, right pipe has barely any pressure or smoke. Took comp test and both have 140 psi in each cylinder. Just finished rebuilding it and making it a 4 mil and ported and what not and now it seems to not run right because of this. need help asap, thanks.

[Eric_C1]

Are the carbs synced? 

[fixitrod]

If you don't have air blowing into the crank case or gear oil getting "sucked in" (bad seal in crank case) maybe try swapping plug wires and maybe plugs.  They spark at the same time up and down stroke so it doesn't matter which cylinder they are on. Then try swapping carbs and check/swap reeds. 

[grantevans713]

It sounds like you are blowing out the spark on one cylinder. This recently happened to me on my trail bike, the fuel\air screw was clogged on the carb. It is also possible that your float height is bad and flooding the cylinder. It could also be getting weak spark from a Chinese stator or flywheel (or both). I would recommend checking things in that order, because things are progressively more difficult and expensive as you move down that list.

[grantevans713]

Also, on stock carbs, the left one has a little metal dot on the bowl. They cant be switched around and this one should always be the left, as this carb has the choke and the bowl is setup for it. Make sure you have the right bowl on the right carb. There is an emulsion hole between the needle on slide and the needle valve that controls float. Make sure this isnt clogged with junk.