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Trouble maintaining full throttle

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Hoping for some expert advice.


I have (besides my horse) Briggs powered cheapo mower. Uses it on the sides of my gravel road, and where I wont take the horse. 


It has developped a problen that I do not quite understand. It is a 17.5 hp 1 cylinder cheap briggs engine. It will take full throttle, also with the deck engaged(app 3300 rpm), but when it gets hot, it is really easy to bog it down a bit. It will drop a few 100 rpm to around 3000, and just be struggling to get up again, kind of surging, also after the deck is free again. then if i slightly take a bit of throttle off, it falls into line again straight away, and if I leave it a few 100 rpm from full 3000-3100, it newer bogs down. It's like it cant feed or regulate itself on the last little bit of throttle.


I have changed filter, made sure there is no vacuum in the gas tank, checked fuel lines, cleaned the carb thoroughly, tried without air filter, and none of it makes any difference. Also checked for false air intake.


I do not have equipment to adjust the carb properly, and am afraid if I mess with it, I can make it too lean and burn a piston. Besides, why should it suddenly need another setting on the carb?


So I'm thinking, can there be something with the governor that could cause this?


I would like to hear from all that has ideas on it. Thanks

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In the states we have a product called Seafoam that works well for cleaning crud out of fuel systems and keeping them operating properly. Hope you can find it or a similar product.

Image result for seafoam

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With the throttle plate wide open it is not getting enough fuel.  Closing the throttle a little makes the mixture richer because it is getting the same amount of fuel at almost wide open and at wide open.  Probably a little, tiny hole is plugged in the carb.  

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I already had it apart, Cleaned out with mini brushes and compressed air. I will find some carb cleaner and give that a go.


For the advice I  :thanks:

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