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Rick, Small Engine Technician
Category: Small Engine
Satisfied Customers: 3844
Experience:  Outdoor Power Equipment technical trainer since 1990, covering eight states.
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I have a lanmower purchased 2013 wit a Briggs and stratton

Customer Question

I have a lanmower purchased 2013 wit a Briggs and stratton 450 series 148cc engine which worked perfectly last season and started well this season but which after about half hours use suddenly started running at about half revs and very little power after staing well the plug is very sooty and ther is some black smoke as the engin hunts .any thoughts on the cause and remidy?
Submitted: 4 years ago.
Category: Small Engine
Expert:  Curtis B. replied 4 years ago.
Check the choke flap in the carburetor. Sounds like choke is closed , letting into much fuel and not enough air. I need the engine model number to see what carburetor this engine has. The 450 is just series and does not identify the engine Need number example,(NNN) NNN-NNNNB1
Customer: replied 4 years ago.

Curtis B thankyou but there does not appear to be a flap in the carb.- when the air filter is removed you can see right down into the jet. the engine is primed by pressing a rubber nozzle three times and starts at the first pull. It then runs for about 30 seconds at the correct revs and then goes to about half revs, hunts and at the lowest point emits some black/grey smoke before recovering to the lower revs..

It is difficult to see the identity number as it is at the bottom of the crankcase and partially obscured by the mower body but as far as i can see the identity number is XXXXX Does this help?


Expert:  Curtis B. replied 4 years ago.

here is link to a similar carburetor. It has no choke, you are correct. So it is a dirty carburetor or a bad gasket or jet plugged. Th e numbers you gave don't show up, but the 450 series uses a carburetor that mounts to the fuel tank,---

Customer: replied 4 years ago.

thankyou. This is not very helpful as the site does not identify the engine installed in my lawnmower and therefore I am at a loss as to the next step. The answer will therefore be to take it to be rectified by an approved Briggs service agent. All very frustration and a waste of my time, meanwhile the grass continues to grow!

Expert:  Curtis B. replied 4 years ago.
Carburetor needs to be removed and repaired or replaced. Sorry.