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Hi, I was wondering if anybody might be able to help? My husband and dad have a 20hp yamaha engine that keeps cutting out whilst stalling on tick over after around 20 mintues and then wont start again. They have followed previous advice changed the fuel filter, cleaned the carb and cleaned the pilot screw but this still hasnt fixed the problem. The engine will start again after being left for a few days but still with the problem. When the engine does run all the water is running through as it should anddoesnt show any signs of over heating. They have used it whilst fishing (they were unaware of this problem at the time) and whilst at full throttle it runs like a dream. As you can imagen tempers and frustrations are starting to show so any advice and suggestions would be greatly appreciated. Many thanks in advance. Tash
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is this a two stroke? 4 stroke?
about how old is this motor? -
It's a 2 stroke and is about 96 - 97 model.Comment
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when it will not start, is there spark to the plugs?Comment
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Have they tried pumping the primer ball after it stalls to refill the fuel system to see what effect this has on the motor starting? Thinking being that at idle RPM perhaps the fuel pump is not doing the job it is supposed to do. That job being to keep the carburetor float bowl full of fuel. The bottom carburetor has an integral fuel pump that can wear out over time. Perhaps the motor is simply starving for fuel.
With respect to the idle mixture screws (aka pilot screws) have they been reset correctly to the factory position? Perhaps someone screwed with them and lost their place. Turn them inward until they are lightly seated. Then turn them outward 2.5 turns. Once the motor is running and idling properly they can be adjusted outward or inward by 1/4 turn if needed to get a better idle quality. Lots of Yams run on the lean side from the factory. If the jets clog up just a bit, or if ethanol contaminated gasoline is used, it can play havoc with the idle air/fuel ratio. Enriching the idle fuel mixture just a bit can oft times make a Yam idle a bit better.
Are the idle speeds set correctly? Spec is for 750 RPM in neutral and 600 RPM when just into gear.
As 99Yam notes, certainly verify that the plugs are sparking when the problem occurs. But it does not sound like a lack of spark issue to me. But...Comment
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