Fun with small-engine carburetors

[Nords]

REWahoo! will confirm that I'm [-]cheap[/-] more frugal than most, but sometimes I just want to use a tool instead of having to spend all my time maintaining it. It's even more frustrating when you're not particularly looking forward to the use of this particular tool.

Our yard's back slope varies from 6-9 degrees, so I "trim" it with a Ryobi two-stroke 30cc weedwhacker using special [-]spinning wheels of death[/-] Aero-Flex blades. The trick is to have something tough enough to hack through the California grass-- but not accidentally amputate your ankle if you slip and fall on your assets. Much to my surprise, this one has somehow managed to last for four years. The weedwhacker, not my ankle.

A couple weeks ago the engine began running erratically to the point where I couldn't keep it going. I noticed that the fuel tank's (plastic) fuel & return lines were [-]spewing[/-] leaking. I used the $15 rebuild kit to make sure the fuel stays on the inside of the engine (with a brand-new fuel filter), and now it starts up fine.

However it won't stay running. When I have the carburetor's butterfly valve shut (at "full choke" or "start") and pull the cord, the engine starts & runs just fine. When I try to open the throttle after a 10-15 second warmup, its interlock linkage also opens the butterfly valve (to "no choke" or "run"). And then the engine sucks in all that fresh air and immediately shuts down. I'd need three hands to simultaneously adjust the throttle, the butterfly valve, and the cutting end.

The spark plug is clean with the correct 0.025" gap but I'm going to replace that as soon as I pick up another one. Four years is probably past its expiration date.

The fuel mixture is correct-- I buy gas in one-gallon increments and use the right 2.6 oz of two-stroke oil.

The butterfly valve has a small screen over its intake, and that used to have a spongy filter over it. However the filter & cover have been lost for at least a year (they're somewhere in that grass!). If that sponge/cover turn out to be the problem then I'd just buy a new weedwhacker.

The carburetor has only one screw to adjust the idle, but my problem is getting the engine up to full RPMs. I'm not even ready to start thinking about idling.

I'm not dealing with a high-performance machine here, so I'm not expecting to have to grind valves or soak pieces in carburetor cleaner. At that point I'd just go buy another darn weedwhacker. However I'm hoping to figure out what price I'm paying for my ignorance. What am I missing?

In the meantime this cool & rainy weather has produced six-foot-high stalks of "grass". I'm going to have to trim most of it with a pair of pruners and maybe a reciprocating saw...

 

[REWahoo]

I'd suggest spraying some carb cleaner in the intake, starting it up and squirting more while it's running.

(And yes, you can get a can pretty cheap)

If that doesn't do it, you'll need to - brace yourself - buy a new one. But take heart because four years of use out there in Paradise is not bad for a weedwhacker.

 

[JmfromTx]

If your gas contains ethanol like mine does the solution is to use a fuel stabilizer like Stabil. I started using it a couple of years ago. It really works and my stuff starts and runs now.

 

[Dimsumkid]

I've been told Sea Foam works miracles on engine starting issues. I don't like gas/oil mixture engines, they seem to have the most problems.

 

[Keim]

I've been told Sea Foam works miracles on engine starting issues. I don't like gas/oil mixture engines, they seem to have the most problems.

I use Sea Foam in the tank of all my cars, and my lawn mower. Has worked great.

I suggest "smoking" the weed eater carb and pistons with it. This involves starting the motor without the air cleaner, pouring some slowly down the carb until it kills the motor (the idea is to draw it into the carb and cylinder head). Let it sit for about 30 minutes. Then start it up. It will smoke like a chimney for a few minutes, but this will clean it out good. You can see how to do this on youtube or their website. It is easy.

I did this to my lawnmower last year. It ran much smoother and started easier afterwards. I also did it in my 1976 Chevrolet Monte Carlo. It smoked like Satans cigar for several blocks. People were pointing and staring. I was a rolling smog violation-must've looked like the beater car from hell. It cleaned out a LOT of carbon, and the car has run great since.

 

[Oddjobdth]

First I would check to make sure you ran the hoses correctly. I've helped a few friends out and that was part of the problem. Second, FRESH fuel. (try buying fuel from a marina. It cost a little more but no alcohol in it) Third, sometime trash can be knocked into the carb, the tiny tubes get clogged and no fuel no run. Get a carb kit and (watch U-tube videos) rebuild carb. It will run like new. Oh, You will have to make an adjustment to that screw.

 

[73ss454]

The problem you are having is most likely being caused by ethanol in your gas. Try and find a gas station that sells non-ethanol gas and your problem will be solved.

 

[Telly]

However it won't stay running. When I have the carburetor's butterfly valve shut (at "full choke" or "start") and pull the cord, the engine starts & runs just fine. When I try to open the throttle after a 10-15 second warmup, its interlock linkage also opens the butterfly valve (to "no choke" or "run"). And then the engine sucks in all that fresh air and immediately shuts down. I'd need three hands to simultaneously adjust the throttle, the butterfly valve, and the cutting end.

The correct air/fuel mixture is occurring only in full choke, as you probably have surmised. So it is leaning out too far when you open the choke. Your mission, grasshopper, is to find out why. Probably gummy gas deposits in the carb plugging up a metering orifice. Force-feeding it carb and choke cleaner should eventually clear it out. You could dump the gas out of the tank, and try mixing up a small portion of a special cleaning fuel using carb cleaner instead of gas in the gas-oil mixture.

You could also lower the ratio of oil used in the special fuel mix to improve the carb cleaner's action, but don't rev it on wide-open throttle very long once it clears up, since lube action will be reduced. Once it's running decent again, dump out the special mix and go back to regular mix. Using good recent gas, of course.

Sta-Bil works wonders as a protectant. But it's just another thing to remember to do

 

[l2ridehd]

Between weed whacker, 2 lawn mowers, chain saw, power washer, hedge trimmer, leaf blower and motorcycle, I have 8 gas engines to maintain. It used to be a full time job to keep them all running. All my problems could be traced back to gas with ethanol. Once I started using "stabil" in ALL gas for these engines, all problems went away. The only ones benefiting from ethanol use is the corn growers and small engine repair shops. The consumer is taking it up the "you know what". Buy some "stabil". available at WalMart" or a like product, and your problems will go away.

 

[justplainbll]

The diaphragm in your carb is probably shot.

 

[Walt34]

One more vote for Stabil. I've used it in all the lawn mower/weedeater/snowthrower/motorcycle engines from day one and so far haven't had an issue. The lawn mower I bought in 1986 and the weedeater a year or two later.

Telly is correct in that it is leaning out too far when you open the throttle. Short of a new carb or rebuild kit try opening the mixture screw a quarter turn at a time and try that. The CRC carburetor cleaner can't hurt and is cheap enough to be worth a shot before you bite the bullet and buy a new weedeater.

And (at the risk of getting political) if you have any energy left after all that write your congresscritters and tell 'em what you think of ethanol in gasoline.

 

[justplainbll]

Overdosing on Stabil can result in formation of sticky red deposits in gas cans and fuel systems.

 

[deserat]

Great ideas for you Nords.....when I think of ethanol, I think of corn syrup (Karo) - isn't that what Paula Deen uses a lot in her cooking?? Hmmm, can a gas engine get diabetes? ;-) Corn syrup clogs up a lot of stuff

 

[eytonxav]

The problem you are having is most likely being caused by ethanol in your gas. Try and find a gas station that sells non-ethanol gas and your problem will be solved.

Some of that old leaded Sunoco would fix him right up. Ah, loved that 260.

 

[ERD50]

I questioned all these ethanol comments on a thread a while back. Living in Corn Country, we've had ethanol probably as long as anybody. Never, ever, ever had a problem using it in any car or lawn mower. Never use stabil or anything else.

I do keep the tank full, and run it a few times over the winter. That's all.

PS - I think ethanol is stupid and bad for the environment, but I just never had a fuel problem due to it.

-ERD50

 

[73ss454]

Some of that old leaded Sunoco would fix him right up. Ah, loved that 260.

The Sunoco 260 might have blown it up altogether.

 

[jim747]

Unless you changed brands of gas, I don't think the gas is causing your problem. I don't care for ethonal but it worked fine for four years so I doubt it decided to start causing problems now.

The idea of a bad diagram is a good one. There is also a possibility your exhaust port is plugged. They can gradually build with carbon until they close enough so there is no place for the exhaust to go and it messes up the fuel/air ratio. I had a similar problem with a Lawn-Boy mower with a 2cycle engine. Loved that old mower. Bought it in 1977 and finally sent it to mower heaven last summer.

 

[TromboneAl]

My Stihl chainsaw was not running well. As soon as I hit the throttle it would die. Turned out I hadn't cleaned the air filter for a while. Doing that solved it. But since your filter is gone...

Also, is the gas old?

 

[73ss454]

With this link you can pick your State and locate Gas Stations that offer Ethanol free gas.
It's set for you Nords.

Ethanol-free gas stations in HI

 

[Nords]

Thanks, everyone, I'm beginning to pick up subtle indications that I might have a problem with ethanol-based fuel. I wasn't even aware that you could buy ethanol-free fuel around here-- I appreciate the list of gas stations.

The two-stroke oil claims that it includes a stabilizer but it and the fuel have been sitting on my lanai for over a year. Long enough for the weedwhacker's fuel lines to rot, which is why I had to replace them.

Telly, you're right-- I could practically duct-tape the butterfly valve in just the right position for the throttle setting that spins the cutters at the perfect speed.

I'll try the carb cleaner and the Stabil. But, yeah, it's tempting to just buy a new one. This one has survived all my attempts to break the clutch and the throttle linkage and the pull rope, so it's probably worth a little TLC.

First I would check to make sure you ran the hoses correctly.

Oh, please.

 

[DAYDREAMER]

Here's another vote for the ethanol being the root cause.

Gas powered equipment that sit unused for long periods of time are having issues because of the effects of ethanol. Problems: Ethanol absorbs moisture and is also an excellent solvent. When ethanol absorbs moisture, the steel float bowls of carburators are rusting. The rust/corrosion then breaks loose, plugging the tiny holes of the jets with in the carborator. The moisture laden ethanol also corrodes aluminum float bowls making aluminum oxide that also clogs the tiny jets. Fuel stabilizers seem to be helping solve some of these issues. The only guarantee not to have issues is to drain the carb float bowl before seasonal storage.

The solvent properties are wreaking havoc in the marine industry because many older boats built in fiberglass fuel tanks. The Ethanol is breaking the tanks down and sending the material through the fuel line.

 

[jazz4cash]

First thing to do always is get fresh fuel if it is more than 30 days old.

Make sure the cap is venting.....loosen it a crack if necessary.

Make sure the spark arrestor is not plugged.....remove muffler and scrape the screen or soak in seafoam if it looks plugged up.

Tape a piece of foam over the air inlet if you need to.

Last resort for me is to pull the carb apart, soak everything in seafoam and replace the diaphram.

 

[justplainbll]

Here's another vote for the ethanol being the root cause.

Gas powered equipment that sit unused for long periods of time are having issues because of the effects of ethanol. Problems: Ethanol absorbs moisture and is also an excellent solvent. When ethanol absorbs moisture, the steel float bowls of carburators are rusting. The rust/corrosion then breaks loose, plugging the tiny holes of the jets with in the carborator. The moisture laden ethanol also corrodes aluminum float bowls making aluminum oxide that also clogs the tiny jets. Fuel stabilizers seem to be helping solve some of these issues. The only guarantee not to have issues is to drain the carb float bowl before seasonal storage.

The solvent properties are wreaking havoc in the marine industry because many older boats built in fiberglass fuel tanks. The Ethanol is breaking the tanks down and sending the material through the fuel line.

+1 Alcohol can act as a solvent for materials that are petroleum resistant.

 

[Brat]

Off subject here but the mechanically inclined might appreciate my 3 yo grandson's comment the other day. He was looking closely at one of his Thomas train engines looked sad, "Grandma I want one with PISTONS! " He seemed to know exactoly what a piston is, I had to tell him that I didn't have one to give him.

Darned if I know where he came up with that.

 

[Nords]

Darned if I know where he came up with that.

Sounds like you might have yourself a hard-wired gearhead there...