Quote Originally Posted by Justin90gsx View Post
Ok the truck is super clean, runs great, but when I give it more than half throttle it hesitates and bucks and goes but is weak.
I think it may be something with the big jet cause I watched the idle jet just drip like it's supposed to and the mid spray really well and the big one kind of trickle?
But has new cap, rotor, plugs, wires, timing set to stock, air filter and fuel filter.
And I ran two tanks treated with Lucas fuel treatment. The truck runs perfect!
Besides at more that half throttle, and only twice it ran great for a min.
Is there valve that could stick inside the carb? Or scrub the jet?
Thanks!
The symptoms you describe are screaming CARB and it's only a matter of time before that Mikuni lays down and won't get up. The main body of the carb is plastic (bakelite) and the throttle blade shaft wears it out- to the point where there is a severe internal vacuum leak inside the carb.

If it runs OK until the underhood temp reaches max then I would bet that is your problem. That's how mine played out.