Export thread

Wouldn't crank, took carburetor apart and cleaned, put back on, cranked first pull, cut grass, stopped and started, cranked right up. 3 days later wouldn't crank again sounded just like before. Bought new carburetor, installed, cranked first pull, stopped it cranked right up again, cut grass. Week later will not crank again, sounds just like it did initailly. What would cause it to crank right after I clean and replace the carb but not few days later.

Would help if we knew which engine your mower has. Please post the model number of the engine as well as the mower so that way we can see if it is the Original Murray. the MTD Murray, the Husqvarna Murray or the Chinese Murray.

ILENGINE said:

Would help if we knew which engine your mower has. Please post the model number of the engine as well as the mower so that way we can see if it is the Original Murray. the MTD Murray, the Husqvarna Murray or the Chinese Murray.

Click to expand...

11A-A2BF758 engine# 09P6020096F1

This may sound counter intuitive, but try replacing the spark plug. those .20 thousands gap plugs are bad for fouling and doing weird things. Not on Briggs, but have seen similar issues on Honda engines that would start and die, or would start and run 5 minutes and die, clean the carb and would run another 5 minutes.

Also something else to keep in mind is those engines are very fuel quality picky. To the point the gas that you purchased yesterday is too old to run today. Sarcasm to a point, but common enough that if one comes into the shop that doesn't start the first thing I do is dump the fuel. The fuel that runs in every other piece of equipment that you own may not even begin to start with the newer Briggs push mower engines.

ILENGINE said:

This may sound counter intuitive, but try replacing the spark plug. those .20 thousands gap plugs are bad for fouling and doing weird things. Not on Briggs, but have seen similar issues on Honda engines that would start and die, or would start and run 5 minutes and die, clean the carb and would run another 5 minutes.

Also something else to keep in mind is those engines are very fuel quality picky. To the point the gas that you purchased yesterday is too old to run today. Sarcasm to a point, but common enough that if one comes into the shop that doesn't start the first thing I do is dump the fuel. The fuel that runs in every other piece of equipment that you own may not even begin to start with the newer Briggs push mower engines.

Click to expand...

Thanks, had already replaced spark plug, and the gas was bought that day. If fuel will not make it work after a day or so, is there an additive?

check the oil level and see if it has gasoline in it.

ILENGINE said:

This may sound counter intuitive, but try replacing the spark plug. those .20 thousands gap plugs are bad for fouling and doing weird things. Not on Briggs, but have seen similar issues on Honda engines that would start and die, or would start and run 5 minutes and die, clean the carb and would run another 5 minutes.

Also something else to keep in mind is those engines are very fuel quality picky. To the point the gas that you purchased yesterday is too old to run today. Sarcasm to a point, but common enough that if one comes into the shop that doesn't start the first thing I do is dump the fuel. The fuel that runs in every other piece of equipment that you own may not even begin to start with the newer Briggs push mower engines.

Click to expand...

Funny you should say that.
I think the engine was designed to use one of those really expensive exotic materials anti fouling spark plugs
My work around was to fit a non resistor plug of the same heat range with a bigger gap of .030".
To do it properly you should mark the flywheel where it passes the coil with a few grid lines then make a wire pointer to fit under the coil mount bolt ( or any other convienant place.
Run the engine with the original plug in it ( Cleaned or replaced ) then using a strobe timing light move the pointer till it aligns with the mark on the flywheel
Now fit the standard plug and do the same , note where the spark happens
Widening the gap retards the spark ( moves the line left ) and reducing the gap advances the spark, ( moves the line to the right )
Keep changing the gap till the pointer aligns with the mark you made .
The timing on mowers that rev slowly & have fixed ignitions is not all that critical

Some of the early engines that used the .020 plug would foul at a moments notice, and on some if you tried to substitute a .030 plug would misfire.

There is no retard in most modern magneto timing chips and most are set to time at full revs ( say 3600 rpm )
Widening the gap retards the spark and in theory should produce a stronger spark.
Widening the gap also increases the resistance so the trick is to use a non resistor plug with a wider gap.
I doubt that the added resistance would have an adverse effect on a mower magneto but it might.
It definately creates problems on old motorcycle magnetos
It depends upon the way the Hall trigger is set up if it will work properly
Other than that you are looking atone of those fancy $30 plugs & try selling one of them to a push mower customer .
I have had a couple of mowers in where they would only start on a brand new fresh plug which was very embarrasing having tested the mower for an hour ( cut my grass ) then it failed to start when the customer picked it up so it got a new plug then a week latter the customer is back because it won't start again.
SO that was my work around BEcause I play with old motorcycles I have a lot of plain ( non resistor ) plugs
Then all that was needed was to pick the same heat range , thread length & seal .
These are not F1 race engines and to be honest the bulk of the plugs on the market could be replaced with a dozen or so plugs
I feel the factory deliberately specifies a plug without an exact replacement to make people think they have to buy the way over priced factory branded plug .
Genuine B & S plug down here $ 15 to $ 20
B2LM $ 5

Now if we start talking 2 strokes that run at 8,000 rpm to 10,000 rpm subtle differences to plug electrodes does make a difference but on a mower engine not so much all that is really important is the temperature range so they neither carbon foul nor glow red so make the engine run on

Plugs are rather like oil every one thinks they are experts while almost none actually understand them