Engine Running Problem


Old 05-12-02, 07:40 AM
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Talking 3.5HP Murray Lawnmower Problem

I have 3.5HP Murray CLASSIC Briggs & Stratton Engine Lawnmower from Walmart $$$. 21"

First year was great, second year problem. (Winterize)

I pull the string lot of time but Murray doesn't want to start. Push the bulb in front couple of time, pull the string works fine.

Here's the problem, when running Murray coughs at regular interval. (Sputtering).

When mowing leave white patches on the lawn looks ugly.

What could the problem be?

What do you think of my guess, Gasket near the carb. or Diaphragm. Are they part of Murray Classic

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Old 05-12-02, 11:00 PM
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As far as the white patches, I would say that you have the blade set too low, or it is bent. The coughing and sputtering could be a bad spark plug, dirty air filter, carb restriction, water in gas, or bad carburetor diaphragm. Let us know what you find!
Old 07-02-02, 07:43 AM
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Yes, my guess was correct and also yours cheese.

The only problem was I purchased spark plug, air filter and oil the whole kit prior to me finding about diaphragm and gasket.

I forgot to mention there was black smoke coming out of at the exhaust. By replacing diaphragm and gasket solved the problem.

Here is how its done unscrew the filter casing and top of motor casing rememering which bolts goes where, noting it in a notepad or so. Unscrew the the five or so screw holding the carb. to the gas tank. There is about 1/2" tubing connected to the carb. at a right angle. You will have to remove two screw on opposite side of this this 1/2 " tubing. Twist back and fourth to take the tubing out.

Underneath the carb. there is 1/4 tube extended inside the gas tank and spring so do be careful.

There is a diaphragm and gasket inbetween carb. and gas tank.
This is what its called, Briggs and Stratton "Diaphragm - Carburetor" #495770 Made in USA. Cost me $6 CND. it's about $2.40 in US. comes in two piece.

My origional Diaphragm and Gasket had a thick piece and a thin piece. What happen was thin piece became wrinkled causing gas to leak. How did it become wrinkled? The SPRING is seated on top of one of Diaphragm or gasket piece which was fabric like material. New Diaphragm - gasket is not fabric like material but thin. Probably there is air pressure involved somehow.

Other possible cause of the problem was the screws holding the carb. was loose due to vibration. So when pouring gas into the tank sometime it leaks over and fall's onto the carb.- tank surface.
Maybe the gas pentarated from the side.

Thanks for the help.

When people has repaired-solved their problems please write back and tell us. Sure would hep us a lot.
Old 07-02-02, 09:43 PM
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Thank you for letting us know how it went. You are correct by thinking that air is involved with the operation of the diaphragm. The diaphragm uses pulses of air from the crankcase to pump fuel from the tank, through the carb, to the engine. Good job!

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