Lawnmower won't stay running

[wkilleffer]

Hello,

Recently, someone gave me a lawnmower that didn't work anymore. It's a Murray with a 4.5 hp Briggs & Stratton 4-stroke engine. It's nice, with a bagger and throttle control up on the handgrip. They said it was about eight years old and had done well until one day it just quit. I like to tinker, so this sounded right up my alley.

It pulls freely. I put a new spark plug in it, and it's getting a spark. The crankcase is full of clean oil. Fuel is getting to the carb. I took the nut off of the bottom of the float bowl and gas ran out. I removed the carb and cleaned it with some carb cleaner and Deep Creep, then put it back on.

After squirting a small amount of starting fluid, I pulled the cord to start. It coughed to life, but only ran for a couple of seconds. I disabled the safety interlock and tried it again. It ran, and continued to run in an unsteady way when I sprayed carb cleaner or Deep Creep into the intake. Once I quit spraying, the mower would quit.

This mower has a square air filter like a mini version of what alot of modern cars use. There's a tube that brings crankcase vapors back trough the intake.

What could cause this? Would a bad carb float make it so rich that starting would be impossible?

Any suggestions would be appreciated.

Thank you,
-Bill

[jtfoxman]

I had a Murray that did the exact same thing. Did you take the bowl off at all? I would find tiny pieces of grass that was somehow getting into the bowl and clogging the little pin hole that sent fuel to the carb. I would clean the pin hole out and see what happens. I would clean mine and it work great for awhile until another blade of grass would clog it.

[wkilleffer]

Did your Murray have the B&S Quantum XTE engine? That's what mine has, and the carb has a plastic float.

The bowl had some debris in it. I cleaned it and will let it sit for awhile. I'm hoping it's not a bad float. I'm not sure how easy it is to get parts.

Thank you,
-Bill

[jtfoxman]

No it was not that engine. If it would be the float there are plenty of sites online that deal with small engine repair and parts.