You really need to post the model number of the engine so we know WHAT 18 hp B&S you have. There are probably about six.

Walt Conner

Yep, about half million every spring! As walt said need more information!

Not to steal Rick's thunder, but I am having the same problem. I just put a new battery on my mower and it just tries to turn every once in a while, otherwise it does nothing. It is a Huskee w/ an 18hp Briggs & Stratton. Here are the numbers: Model: 31H777; Type: 0235E1; Code: 040109ZE. Any help you could give me would be appreciated.

First, have somebody check that new battery to see if it is fully charged. Then check the oil in the engine. Wipe the stick after the first pull, then re-insert the stick, and pull it out again to get the true reading. If oil is correct, then check the battery connections, and make sure you didn't hook the battery up backwards. It should be red cable to the positive post of the battery (+) and black cable to ground.(-) (Tractor frame.) Check for rust at the frame connection. And at the post connection points.
Also, always use new bolts and nuts and lock washers in the battery cable connection points. It sounds like maybe, the battery isn't fully charged! It happens!

Most common problem with these engines with this symptom is the valves needing adjusted. I have detailed instructions at address below, put in proper format and remind me.

Walt Conner
wconner5 at frontier dot com