Small engine carb question
 

I started my weed-wacker up this weekend for the first time in months (possibly since last year). It runs fine at idle, but when I get to wide open throttle, it dies. What could be the cause? Too rich, too lean? I know very little about fixing these things.

It runs on a gas/oil mix, and I mixed up the fuel in the tank in case the oil settled over time.

Thanks in advance.

Mine has done the same since it was new. What brand is it?

Um, weed-wacker brand? I don't remember. I'll check tonight.

Mine used to run really well.

Make sure you've turned the choke off after it warms up

pull, clean the aircleaner. spray some carb cleaner at the carb.

use new fuel (although this is a long shot.)

Rev the hell out of it then put your hand over the carb choking off all air. This pulls gas and oil through the carb which will clean out most dirt.

If it dies at full throttle then it is probably getting too much fuel. Something is wrong and not just not improperly adjusted. If you do not alter the factory settings then you never need to touch them. These machines are made as close to maintenance free as possible and are disposable.

If you have too much fuel:
change spark plug
clean air filter
try to clean carb - it will barely resemble a carb - more like a block of aluminum with a couple of holes in it. Try some carb cleaner. Some models are not serviceable.

Let us know how it works out.

I believe there is one mixture screw on the carb. Screw it all the way in and count the turns precisely. Remove it and spray some carb cleaner threw it. It just needs the varnish cleaned out because it hasnt been run in a while. Reinstall the screw and turn back to where it was set before. That carb has a diaphragm pump and gets clogged with the fuel mixture residue. Blow her out and she willl be fine.

I had a similar problem with my 2 stroke leaf blower- it would not rev and I thought it was mixture. I had already put a new plug in and it didn't help. Increased the plug gap and ran like a champ.

It is a Homelite.

I checked the filter, and it is pristine, since the thing has hardly been used.

I don't understand why it would have gone out of adjustment just sitting in my garage. Clogged makes sense.

I have turned the choke off once it's warmed up, with no effect.

I will pull the spark plug and check to see if its fouled.

Then I'll pull out the filter and spray some carb cleaner.

I'd prefer not to pull off the carb, since I'm not that handy. Well, I'm sure I could get it off, putting back on properly would be a bit of a problem.:D

Thanks for all your suggestions. I hate to take it to a shop if it is something I can fix myself.

Subscribed, I have a Homelite that never ran worth a crap. I always borrow my brothers Echo, which is the Porsche of those engines (he lives two doors down, so its no big deal to borrow).

I don't understand how those things work without a reed valve :confused:

If it's been left with gas in the tank and in the carburetor then my money is on it being clogged up with gunky fuel deposits. As all the useful stuff evaporates off the gas it leaves all the horrible stuff behind and it can get quite syrupy. See what Robert said about cleaning it out. Get some decent carb cleaner and spray it in there and give it a good soaking. Maybe leave it in there overnight and try starting it again the next day.

Had a Stihl that acted similar. I checked everything (I thought). Gave up, took to small engine shop. He removed the muffler, showed me the exhaust port.
What should have been a good sized, oval opening was almost closed shut with oily/carbon buildup. He cleaned the exhaust port and muffler of crud ...ran like new.

According to him, (perhaps it's only Stihl products?) people do not run them enough at FULL THROTTLE. He said idling and mid-ranged RPM chokes them and lets the oily/carbon buildup happen.

Reed Valves
 

Rick-1 It depends what kind!

Some do have a valve but not in a reed configuration. The crankshaft is machined with an axial port down the center. It has an opening in line with the carb and acts as a rotating valve. Some 2 strokes have a series of reed valves and function precisely the way you are thinking. This inexpensive homelite motors have reeds. They work fine for what they are designed to do.

Bob

If you haven't gotten it running right yet, I'd say you probably don't need to remove or clean the carburetor. I would dump out the old fuel and put in a fresh mix of fuel.

Then, if you just turn the adjustment screws (probably two of them, one for idle, one for high-speed) counterclockwise about 1 turn, then try to run it for a bit. Readjust the screws back to their original position, and see how it runs. All you're doing by adjusting the screws is allowing any debris to clear through the jets.

I just took my Echo GT2400 weed wacker (string trimmer) into my local hardware for a tuneup since it was stalling upon acceleration. They changed the filters, spark plug and fuel and told me not to use StaBil, but to empty the gas tank at the end of every season. Seems the old fuel causes trouble even when it's mixed with StaBil.

Usually a small engine that won't take throttle is too lean, in my experience. Try covering the air intake slightly with your fingers while you try to rev it. If that works it's too lean.

You probably have a mixture screw, an idle screw and a high rpm setting. Likely only the mixture is wrong.

Getting a 2-stroke to start and idle should be the hard part.

One other likely culprit - the carb is loose and is sucking air past the seal. They vibrate loose a lot.

As for how those little carbs work? I've never really understood them.

With these newer machines, what you will find to be the weak link is the clear plastic fuel lines. These develop small pin holes that you cannot see and will cause bubbling in the fuel lines. will caused the weedeater to quit running at full speed, and will sometimes cause the unit not to start at all. I have a 1yr old Sears model (dont know who made it for them) and I have just replaced all the fuel lines due to the same problem...... got replacement fuel line at a local Ace hardware store by the foot.... Hope this helps.....