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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 450 engine,I have just decoked the engine,changed

Customer Question

I have a 450 engine,I have just decoked the engine,changed the oil,new plug which is sooty The engine is mis-firing and running rough,compression seems ok,lack of power also.Any suggestions for better running.David Meadowcroft

I also checked the magneto air gap & set it at

0.20mm,Plug gap 0.75mm.Ran engine with &without air cleaner,no change in running.Re-ground the valves in.Used an upper cylinder cleaner (Redex) to clean carburetter.

Submitted: 4 years ago.
Category: Small Engine
Expert:  Curtis B. replied 4 years ago.

Have you checked the carburetor needle valve and float? This is a Briggs engine isn't it? Here is link to carburetor site.

Customer: replied 4 years ago.

There is neither needle or float,it is a vacuum type attached directly to the tank,that is why I used Redex in the petrol and directly in the clean

any jets.The crankshaft is vertical as the engine is on a mower.It is a Briggs

engine 450 series Model 90000 Serial no02022849

Expert:  Curtis B. replied 4 years ago.
The tank mounted carburetors were listed. Did you look at them? You may need a new diaphragm with tank mounted carb.
Customer: replied 4 years ago.

Yes,none of the carbs listed are like mine,they are similar I will have a closer look at the one on the engine.There may only be a joint between

carb and tank.,I have already checked the securing screws for tightness

but did not strip down the carb.

Expert:  Curtis B. replied 4 years ago.
What is the engine model number? example 123234-0123_b1