OT - any small engine gurus?

jacksonpt

jacksonpt

New member
I've got a McCulloch backpack style leaf blower that isn't running right... hopefully someone can help me figure out why.

The blower starts up after a few pulls every time, just like it should... I prime it, set to full choke, 2-3 pulls and it almost fires. I then set it to half choke, 1-2 pulls and it fires up.

At this point, it seems to be running as it should. I let it warm up for a minute or two, then set the choke to run and it stalls out. Regardless of how long I let it warm up (1 minute or 15 minutes), as soon as I move the choke to the run position the engine stalls out.

The last couple of times I've used it, I've just left the choke set to half so I could get my work done. It runs for about 30 minutes before stalling out. At this point, it doesn't restart. The engine still pulls and turns over, but it doesn't fire.

The gas/oil is mixed as it should be and I ran some staybil with fresh gas last time out, so I don't think its a gas issue. It fires up pretty quickly/easily every time, so I don't think its a spark plug (though I'm not sure the last time the plug was changed).

Any thoughts? Obviously mechanics isn't my forte.

TIA.
 
The carburetor is clogged. The choke is an enriching circuit. On your engine it typically restricts the airflow and thus changes the air/fuel ratio. With the path of fuel slightly restricted, when the flap allows more air in when it's set to "run" it dies.
1) If you aren't running some sort of ethanol gas treatment in your small engines, start now. Ethanol is the #1 problem for small engines.
2) you can try running "Sea Foam" in the gas and hope it will save you from taking the carb apart and cleaning it.
3) Try to carefully "tap" on the carb with a screwdriver handle in hopes to dislodge the clog.
 
Depending on your location as well some gas stations offer recreational fuel that contains no ethanol. I agree on the carb being gummed up.

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Carb gummed up is the most likely issue. While you're at it, you should clean the air filter. It is probably oiled foam and isn't too difficult to do, though I sometimes cheat and just buy a new one.
 
check the air filter. Take it out and rinse it with gas, let it run thru both sides, then let it air dry. Put it back in and see if that helps. Or you could buy a new air filter of your feeling froggie

My rototiller was doing what you described, i did that with the air filter and in ran like new again :-)
 
Thanks everyone for the tips, ill give it a shot tomorrow... I'm hoping to get my local mtb trails cleaned up.
 
if its a two stroke engine which most are then you may also want to clean out the muffler . i know you may first laugh but the muffler on many of them is plates of steel and they have holes in each plate that dont line up . small 2 stroke engines should be run at full throttle and if they are not they dont run their exhaust gasses hot enough to completly burn off all of the 2 stroke oil then the muffler actually gets gummed up ie. it gets clogged and the exhaust gasses cant flow enough because there is to much back pressure .simple to clean and something that is usually over looked . many people just throw away their tools after a few years and they wont start . they should last for many ,many , years with proper maintence and also knowledge of their required running paramiters .
it costs $45 for them to chean it for you and it takes five minutes to do .
yes an additive is now needed if your running gas with ethanol in it at any %.
some of the high octane gas no longer has ethanol in is so do use that if you can find it .
 
Although probably not the problem, while you're at it, it never hurts to look at the spark plug. It might be dirty enough to need a wire brushing, especially since you've been running it rich lately.
 
Ok... I took everything apart today, both on the intake side and the exhaust side. There was a bit of build-up, but nothing that made me say, "whoa, that could be the problem."

I wiped out what I could, put everything back together sprayed in some carb/choke cleaner, changed the spark plug, and gave it a pull. It sputtered a couple of times, then fired up. It ran for about 10 seconds with the choke at half, then died.

It hasn't started since.

Any other suggestions?
 
Take the carb apart again. :D

All it takes to make the thing run like crap is one imperceptible speck of crud in the wrong hole.

Dave, I agree, it's too bad that most people consider these things disposable. Heck, my snowblower is older than me and it runs like a top.
 
Heck, my snowblower is older than me and it runs like a top.
Click to expand...

Hah, my neighbor's BEAST might challenge for that title :)

Jackson, try and start it a few more times squirting carb cleaner in it. If it repeatedly starts that way, sputters, and dies you probably have a carbuerator issue. Since you've replaced the spark plug, AND you're getting compression/fire, it's probably not enough fuel getting in there. DWZM is right, it just takes a tiny little bit of something in there to muck everything up
 
I took everything apart again. At this point, I can't imagine its the carb... the thing looks polished clean (though I'll yield to you experts if you insist that it is still the culprit).

I tried starting it several times, but it doesn't fire. I've tried both spark plugs (just to be sure), and nothing with either one. It still cranks, but doesn't fire.

At this point, unless you guys have some other simple suggestions, I'm probably going to have a small engine shop look at it. I'd really like to have it running this week while the weather is still nice.
 
Wow, ok that's a definite winner. My neighbors' is probably 60's material.

Jackson, have you tried spraying carb cleaner into the intake manifold or the air intake and starting it? If it fires for a few strokes and dies when you do this, you know you have good spark, compression, and exhaust. It's not always possible to spray some carb cleaner in while starting it... My in-law's snowblower has no intake air filter (bizzare) and the intake is right up aganst a shroud that holds the starter switch, solenoid and all manner of things, so you can't realistically spray carb cleaner in it and get it to start without removing all those essential parts. PITA. Not sure what your leaf blower is like. Does it have an inlet air filter?

Also, as for the carb, does it have a float valve? Have you made sure that's functioning properly? You can clean it out all you want but if the float sticks shut, no gas gets in the cup there and then not into the nozzle, and thus not into the engine. And I've seen carbs which looked FINE, but after I've ran a needle down through the fine port that sprays the gas into the thing, they fired right up. Sometimes it's just a TINY bit of schmutz you don't see.

Anyway, if you can get it to fire with carb cleaner, your problem is carb/fuel. Just as a final thing, you've tried fresh gas yes?
 
der_wille_zur_macht said:
Oh, I'm not worried about challengers when it comes to competitions of who owns the oldest gas powered equipment. Pretty sure my 1939 farmall has that title fairly secure. :lol:
Click to expand...

I still use my Grandfather's '53 (we think) Gravely Model L.

Safety features? Yeah, if you run over yourself, it'll automatically shut down once it runs out of gas.
 
very nice saftey approved super tecnique, gotta have my brand new snowblower updated to that feature as they hardly offer it anomore !
 
take the spark plug out, put the cap on, ground the end of the plug and pull the cord. If you see the spark, you are good there. You can try starting fluid in the intake but the primer bulb already forces gas in there.
When you say you took apart the carb, did you remove the jets and needle. Did you blow carb cleaner through all the little passageways and then use compressed air?
 
Dropped it at a shop today... I won't have time to monkey with it the next couple of days so I bit the bullet.

Thanks for all the help.
 
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