Briggs & Stratton 18 Twin II will nly run on full choke

My buddy got this 18 Twin Briggs and we can't seem to get it running properly I was hoping someone might have an idea. I'm trying to think of all we've tried. Ok, we put a new fuel pump kit, flushed the tank, new filter, cleaned the carb, new plugs, the motor runs very smooth at full throttle as long as it is choked. When the coke is let off it will stull run fine, but when you let it idle and try to throttle up it dies. Seems to me like it is sucking air downstream of the carb, but we checked all the gaskets and made sure everything was tight. The last thing I can think of trying it a bit of RTV sealant on the intake gaskets...

Is there not a mixture screw??? I had this problem with a 12.5hp opposed briggs, but after a while it sorted its self out. you may want to take the carb to be ultrasonically cleaned, that has worked for me on many carbs for motor bikes and the like.

Yeah I adjusted the main jet and the idle mixture and even very rich it still has trouble. I think I will dip the carb in some good cleaner, altho I have used spray cleaner and compressed air on it. Nothing was visibly clogged....

Sounds like what my 17hp opposed in my MTD is doing. I waited for winter to work on it but was assuming it was the carb needing cleaned. If you've done that and still have problems, I might also. Hope you figure it out.

mine only ran half choke so i ripped the carb apart and everythig had corosion all over it especially the main jet all the holes were corroded over (explains why its not geting gas) so i ordered an overhaul kit so im waitin on that:)

My 99 murray hydro ran horrible - even after multiple carb scourings- so bot a new carb kit ( comes with gaskets, pump internals) - after the rebuild it ran nice n smooth. The new gaskets are the key to making it run better - make sure you get the correct gasket ( comes with a few different ones) or it wont run at all.

Youll need the motor numbers ( all of em) and how many screws hold the pump to the carb ( mine had 3) - it was like $20 from my local Cub cadet dealer.