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My mower has developed a surge when warm. If the mower deck is applied the surge goes away and it runs strong. Turn the pto off and it surges at high speed and will kill at low speed.
Sometimes the Rpms won’t even come down when the throttle is lowered, just stays at full.
To me it seems like 2 different problems. Maybe a fuel issue for the surging and a linkeage for the rpms not wanting to lower. ?
 

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Father Deerest
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Run a heavy dose of seafoam through the fuel system for a few tanks and see if that clears anything. It's not the cure all but I've had it work in several machines, worst case take the carb off and run a strand of thin wire in the ports and soak it in carb cleaner.
 

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Sea foam is a great product, I mix up some in each five gallon can when purchasing fuel, then it's got a fighting chance. All of my other small engines run on E-94.
 

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I recently bought a nice X520 that had been sitting for a year and it surged at idle but ran ok at WOT. I poured the required amount of Seafoam into the the tank and ran it for about thirty minutes and it cleared up. Not guaranteed but it is a cheap and easy first step. After that, all of my experience with Kawas is the carb. I believe the Japanese culture is more refined than ours when it comes to taking care of machinery. They tend to be more focused on things like cleanliness and care of fuel and maintenance. That is why the Mikuni carbs are so much trouble for us. They were built for people who pay attention to their fuel and what they put into their machines. I do know that the Mikuni carbs have smallest orifices in a carb that I have seen and it takes only a mite that is almost not visible to change the operation of the engine. Good luck with your issue.
 

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. I believe the Japanese culture is more refined than ours when it comes to taking care of machinery. .
I would bet that the vast majority of made in japan Kawasaki OPE engines are exported out of japan.

I think the problem with the motors using 2 bbl carbs is that the carbs are too big for the requirements and this reduced airflow through the carb makes the jetting more critical. I know on the GT245 I had the carb had a built in limiter that kept the butterflies from opening more than about 1/4 to 1/3. That means that 2/3 to 3/4 of the potential airflow is not being used, i.e. the carb is too big. Most likely they had to do this due to poor mixture distribution between the cylinders. This is also why the carbs on these motors have different jetting on cyl 1 than cyl 2. I can also imagine that it is common for the jets to be put in the wrong side when the carb is rebuilt by a shadetree mech.
 
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