LAwn Mower.????

i have briggs & stratton 4.5hp mower. it was made in 2003 it says on it. its fairly new. it has no accelerator. i think it rrevs higher when u start mowing. but the prboel is that when u start it it starts then runs fine for 5 secs and then almost turns off. then goes to normall and repeats this patter. The fuel filter and the filters are fine. why is it doing this?>>???

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3 Responses to “LAwn Mower.????”

Lawnboy & Luna says:

March 9, 2010 at 6:45 am

I would check the air filter. It sounds like it runs OK when cold, and it is tuned to run "lean" cold, but when it warms, it does not get enough air. Check the air filter, and I’ll bet it is dirty. If not, go with the guy suggesting the bad gas. You don’t have a bad plug. Generally, air filter, plug, and gas are 90% of mower problems.
Fr8Train_us says:

March 9, 2010 at 6:45 am

My mower does the same thing, it will do that until it has run for a few minutes and warmed up. You might have some bad gas, (i.e. it is old or has water in it) or it might just need a tune-up. I would have it serviced, as it is getting to that time of year again.
renpen says:

March 9, 2010 at 6:45 am

The most likely problem is the carburetor. These engines have a diaphram carb and need to be cleaned and rebuilt as the diaphram fails. It is not a hard job. You remove the gas tank and carb together. Then remove the carb and clean it out and put it back together with a rebuild kit. The kit costs about $10-15. Make sure that you note how the springs and rods attach to the carb. I sometimes use digital photos to make sure it goes back together right.