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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 13581
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a 2010 Simplicity ZT3500 with a &S 24hp professional

Customer Question

I have a 2010 Simplicity ZT3500 with a B&S 24hp professional series (44m777). The issue I am having is the mower runs a little rough at first and then gets up to rpm slowly. When I engage the pto the rpm's drop way down and then gradually gets up to speed again. I have replaced the spark plugs, air filter, changed the oil and cleaned the deck. Belts are in great shape. I had a similar issue year before last and a new battery fixed the problem. I checked the voltage this time with the mower running and it is at 14.1 volts. Thanks for any help or suggestions you may have.
Submitted: 1 year ago.
Category: Small Engine
Expert:  Curtis B. replied 1 year ago.

I would do a cylinder balance test. Loosen the spark plug wires, and with engine idling, remove one wire at a time. If engine dies when either wire is removed, the opposite cylinder is not firing.

Expert:  Curtis B. replied 1 year ago.

If that is the case, check for spark , and if no spark, the coil on that cylinder is bad.