[AT] Briggs stumbles when load increases

ken knierim wild1 at cpe-66-1-196-61.az.sprintbbd.net
Wed May 11 16:08:52 PDT 2005


On Tue, 2005-05-10 at 06:51, Len Rugen wrote:
> I have a 8 HP I/C Briggs that is about 15 years old but has been well cared for.  It starts on the first pull and doesn't use any oil.  Its problem is that when a load hits it, it "stumbles" and nearly dies, then runs rough for awhile.  If the load stays constant, it will handle it, but if it varies, it runs bad.  It has a float carb, and will leak when not running unless I turn off the fuel, so I know it needs at least a float valve.  
> 
> What else could it be?  

As mentioned, the carb is the most likely suspect, and a kit would be
where I'd start. 

The other option is that you've got an old plug in it; replace that when
you go after the carb (or heat the plug up with a torch until it glows
orange and burn the carbon off it, then blow it off with an airhose to
thermally shock and blow off the rest of the crud).

The plug can be tested by leaving a spark gap in series with the plug.
The I/C series I've worked on generally had electronic ignition and thus
had good spark so they would generally light the plug but you could have
some buildup on the plug.

Does putting on some choke when it starts to stumble help at all? I'm
assuming you've cleaned the air cleaner as well; I've seen some that
were running a bit "rich" from all the dirt on the filter and that'll
cause a lot of problems.

Does the compression feel significant when you slowly pull the rope?
Seems to me the I/C engines had valve rotators and better valves but the
less expensive brethern would carbon up the valves or wear them down,
causing loss of compression and all manner of horsepower loss (though it
usually made them a beast to start).

Let us know what you find.

Ken






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