4 stroke trimmer

[Trunk Monkey]

I've got a 4 stroke Yardman/MTD trimmer that's been awesome for a long time, but this week, after I start it if I give it any gas it dies. I checked the air filter, it's fine, noticed it was a little oily so I cleaned it. It will start first pull and idles fine, but give it gas and it starts to bog until it kills. Fuel is new, nothing else unusual. It was idling high so I backed that down a little. Any ideas where to start troubleshooting?

 

[D'Animal]

Plugged spark arrestor?

Have you ever had to adjust the valves?

 

[Trunk Monkey]

I was hoping you'd reply Dan, thanks. Nope, never done anything to it, filled with with gas, changed the oil a couple times. I'll check the exhaust end of things. It's in a shed with the occasional mouse, maybe they stuff some crap in there.

EDIT - nope, pulled the muffler completely, still dies with throttle. Doesn't smell like it's flooding out.

 

[splitshot]

Fuel lines going south? Sucking air?

Fuel additives lately have been trashing ours if the guys don't store them dry.

 

[AJP]

It will start first pull and idles fine, but give it gas and it starts to bog until it kills

same same with my Honda 4stroke weed wacker. It ran great for a while but despite having less than about 20hrs (+/-) it developed the same symptons ... I checked for plugged exhaust and valves and replaced filter and fuel line.. FINALLY took it to the local Honda Power Tool centre. They declared it needed a new carb kit .. and after I picked it up .. runs great again. Said the rubber parts were as hard as a rock..and blamed the ethanol in the fuel I was using .. was advised to use premium only.... YMMV

 

[John McVicker]

same same with my Honda 4stroke weed wacker. It ran great for a while but despite having less than about 20hrs (+/-) it developed the same symptons ... I checked for plugged exhaust and valves and replaced filter and fuel line.. FINALLY took it to the local Honda Power Tool centre. They declared it needed a new carb kit .. and after I picked it up .. runs great again. Said the rubber parts were as hard as a rock..and blamed the ethanol in the fuel I was using .. was advised to use premium only.... YMMV

This indeed could be your problem but the 1st place I would check is your in tank fuel filter & then look for any breaks in your fuel lines.

John

 

[Trunk Monkey]

Fuel lines are fine. Odd thing is when I was checking them after I did, I started the trimmer again and it ran like it should, could run up full throttle. Stopped it, started it, back to running bad. WTF? Now I can feather the throttle up to about 2/3rds and have enough power to work, but open it up any more and it will kill.

 

[John McVicker]

Fuel lines are fine. Odd thing is when I was checking them after I did, I started the trimmer again and it ran like it should, could run up full throttle. Stopped it, started it, back to running bad. WTF? Now I can feather the throttle up to about 2/3rds and have enough power to work, but open it up any more and it will kill.

What about your fuel filter ? Take it out/off & see if you can easily blow thru it. S/b nice & easy.

Same thing for your fuel line. Sometimes you can't see the break/hole. Remove the fuel line, plug up one end & blow thru the other end. Doesn't take much to affect these small engines.

Another trick that sometimes works is to spray short shots of carb cleaner into the carb while feathering the trigger. Do this a bunch of time while trying to not kill the engine.

John

 

[Trunk Monkey]

And now this morning it won't start at all.

Will check filter this afternoon and lines.

 

[John McVicker]

And now this morning it won't start at all.

Will check filter this afternoon and lines.

Do the carb spray trick too. Sorry for your problems.

John