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Yamaha 50 2004 4 Stroke - carb issue?

WF36

New member
Hi Folks,

Thought I would pick your brains on an on going issue I have had with my 2004 (carb’d) Yamaha 50 4 stroke.

Ever since I have owned it, always hard to start when cold. Have checked the prime start waxes and they appear to function OK. I wonder if this could be related to my other issue which I assume is related.

Once I feel the engine is warmed up after a few mins at WOT I only seem to get 5300RPM. But can be up to 5/10 mins later suddenly full power appears to kick in and it will happily rev up to 6100RPM for a long time with no issues - Trim doesn’t affect this.

Another thing that I note is that when you floor the throttle from idle it almost tries to cut out and feels like something isn’t holding the power back, but then suddenly picks up - hope that makes sense.

The engine also coughs and splutters on ticker over/ low RPM

I have tried all the following: new fuel, different fuel line/tank, full service. Carbs have been dismantled and cleaned with high pressure air - perhaps they need ultrasonic cleaning?

Wondered if anyone one had any further thoughts on what the issue maybe? Thanks.
 
My F60 has similar starting issues and the only thing that made
a difference was to pump the ball until you can hear fuel pumping into the engine.
Even if the ball feels firm, pump until you hear fuel entering the carbs.
also run a 1/2 can of seafoam in a 5 gal tank.
If that doesn't work, carbs likely need another cleaning.
 
Everything I have read leads me to believe that the carburetors need to be cleaned. Ultrasonically. In a heated solution. Passageways and orifices rodded out and confirmed to be free and clear of debris.
 
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