5HP Briggs pulsating

[Cliff_Johns]

I have a Dr. Trimmer that's about 8 years old or so. It has a 5HP electric start verticle shaft Briggs & Stratton engine.

The problem I'm having is that when it's idling, it pulsates, like it's getting more gas then less then more then less. When it's under load it runs great. When I disenguage the cutter, it starts pulsating again.

I pulled off the top plastic and cleaned the various springs and levers that are near the air intake, hoping that something was just sticking, but it didn't seem to make much difference.

Before I take it apart further, is this a common problem with small engines? What should I look for? I hope for some sage advice from someone so I know what I'm looking for when I start dismantleing it. My knowledge of small engines is limited, so don't worry about insulting my intellegance by stating obvious possibilities. It's quite possible that I missed the most obvious thing.

Thanks for any help you can offer,
Cliff

 

[nobull1]

Remove air filter and start for a couple of seconds.If it runs smooth dirty/contaminated filter.This happens quite often if the motor gets flipped over.You don't want to run it long like that or have any dirt handy that could be sucked in.Easy place to start, after that it gets a little more complicated but not rocket science /forums/images/graemlins/grin.gif

 

[Cliff_Johns]

I did remove the air filter. It was still very clean (i'd replaced it last year). I tried running with the filter off, but with the same results.

Good idea though. Any others?

Cliff

 

[nobull1]

How about some more info such as first time used this year, worked fine when put away last year,didn't run dry and remove remaining old gas etc etc etc

 

[livincountry]

I have an 18 HP B&S that has done the same thing from time to time over the years. I take mine to the dealer for spring prep and it comes back fine. He said the carb needs to be cleaned. He said today's fuel plugs them up.

 

[Cliff_Johns]

OK,
It did this last year, though not as bad. Last year it was a bit annoying, but this year the whole machine turns left and right with the force of the on-then-off pulsing unless I enguage the cutter, then it's OK. I have not used it this year yet except to start it up and try to make it stop pulsating. I use Stabil in the fuel regularly -- and left fuel in it over the winter. I figured the stabil would keep the gas from turning bad on me.

It starts OK, though the electric start won't start it. It needs a pull -- always has.

Cliff

 

[Cliff_Johns]

</font><font color="blue" class="small">( He said the carb needs to be cleaned. He said today's fuel plugs them up. )</font>

I wonder how today's fuel is different. No lead?

Can you clean a carborator by spraying gumout down it's throat while it's running, or will that blow up the engine?

Cliff

 

[nobull1]

I think livincountry has your answer.What I find is it is best to do is run dry than remove all remaining gas from tank.It is a good idea to take the carb off and clean in the spring anyways.After you do it once it's no big deal.

 

[Molerj]

Take the bowl off & clean out the carb & all the openings with spray carb. cleaner. Spray up into the center of the carb; main jet. If their is a hole in the bolt that holds the bowl on, make sure it is clean. Sounds to me the idle circuit is plugged up a tad. Not an uncommon problem in small engines. Today's fuel is different & problems do occur when the fuel gets stale.

 

[KENSFM]

Sounds like the governor and linkage may need adjusting. Have you checked this out?
Ken /forums/images/graemlins/smile.gif