Hello, I have a Ariens Zoom 1640 zero turn mower and it starts slow, engine turns over good, when it cranks up on choke it has to run a little while on choke and then you can return to idle and it does OK, may die a few times but it will idle after a while. As soon as you go to 3/4 throttle the engine starts to surge, if you go back to idle are just below 3/4 throttle it is OK.If you go pass 3/4 throttle to about mid choke it runs find,you can cut grass just like it should.Have replaced all fuel hoses from both tanks and all filters. I put a vac.gauge on the engine hose to the fuel pump and it reads about 3 or 4 inches of vac, but it flutters a lot.New fuel, no water in fuel bowl.I don't know how to check the fuel pump. Hope you would be willing to give me some direction. Thanks for your help and troubles

Sounds like you have a main jet that is partly blocked.
Would recommend removing carburetor and cleaning ,
Luck .

Thanks for the help, I resoked the carb, blow it out and it does not surge now .Thanks again. I posted an other problem about the steering under garden by mistake, thanks