2013 Yamaha 25 hp 4 stroke carb issue?

[ktoelke54]

I’m in the process of giving this motor a tune up. It idles smoothly runs up good but— there is a spot between idle and full throttle where it bogs down. It’s only noticeable when the throttle is advanced slowly, then it is very apparent. I have disassembled and cleaned the carb, soaking and blowing out the jets, but don’t have anything small enough to insert in the idle jet. I’m wondering if this is where the problem is. And advise appreciated, thanks.


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[turbotodd]

Usually if the idle jet is restricted or plugged, it will not idle properly, if at all, and that applies to almost all of the Yamaha's (at least all the ones I've worked with). A bog is "usually" a function of an accelerator pump issue. That could be due to a restricted nozzle, restriction in the bowl, check valve misplaced in the bowl (usually apparent by a loose snap ring), plunger stuck, or a leaky bowl gasket. The nozzle is not replaceable. The orifice in the bowl is also not replaceable so if it's plugged, or the nozzle is plugged or restricted, you have to replace the carburetor or the bowl, or both depending on what's restricted.

Does it start easy when cold? How is the oil level? Those should be about 1/2 to 3/4 way to the high mark on the dipstick. If over-full, it can affect how it runs.

 

[ktoelke54]

Usually if the idle jet is restricted or plugged, it will not idle properly, if at all, and that applies to almost all of the Yamaha's (at least all the ones I've worked with). A bog is "usually" a function of an accelerator pump issue. That could be due to a restricted nozzle, restriction in the bowl, check valve misplaced in the bowl (usually apparent by a loose snap ring), plunger stuck, or a leaky bowl gasket. The nozzle is not replaceable. The orifice in the bowl is also not replaceable so if it's plugged, or the nozzle is plugged or restricted, you have to replace the carburetor or the bowl, or both depending on what's restricted.

Does it start easy when cold? How is the oil level? Those should be about 1/2 to 3/4 way to the high mark on the dipstick. If over-full, it can affect how it runs.

It starts easily and runs fine other than that dead spot when you advance the throttle.

So where should i go next with sorting this out? Would a carb kit help? The oil level is a little below the full mark when cold.


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[turbotodd]

With gas in the bowl, look down the intake silencer side of throat of the carburetor. You may have to remove the silencer to see in there. With your hand, move the throttle lever to open the throttle. You should see a stream of gas being pumped through the throat. If you're just seeing a dribble or nothing at all (which I suspect is the case), chances are that the nozzle is plugged or linkage broken or whatever for the accelerator pump. A properly functioning accelerator pump on that carb should have a somewhat powerful shot of gas being shot out of the nozzle.