1985 Yamaha 90hp not running right

[boydog40]

carbs have been cleaned with new kits, new fuel pump, new plugs, new plug wire boots, compression is even on all 3 over (118), still just not right, sounds and feels like it is running on 2 cylinders but I know for a fact im getting fire to all 3...........
driving me nuts trying to figure it out, im all out of ideas.
you guys have any suggestions??
thanks

 

[99yam40]

with the silencer off of carbs feel the suction on each carb with you hand while running to see if they all have the same suction .
Could you have a problem with the reeds?

A motor needs good compression, good spark, spark at correct time(timing) , and the proper fuel to air ratio in the cylinder.

So you must be missing one or more of these for a cylinder not to fire and create power.

The link and sync procedure in service manual needs to be done every time after reinstalling carbs to make sure all are set up properly

 

[robert graham]

Maybe install 3 new/clean plugs, take it out and run the motor, turn it off and carefully inspect plugs for any signs of carbon or discoloration that could give a clue to the problem. When you cleaned the carbs did you do them one at a time so as not to mix the jets, as they could be different from carb to carb? Are the carb floats set to the correct level?....