small 2 stroke engine HELP!
 

I've about had it with this leaf blower. It's a Stihl, not top o' the line but a good one. I run premium gas using the Stihl label oil at 50:1. Sometimes it runs great, more often not so much. 1 of 2 things happens that I cannot figure. 1) it starts and idles fine but won't take fuel without bogging (fuel filter/air filter OK) 2)starts and runs fine for awhile then starts to bog. Close the throttle the idle stabilizes but won't take fuel and bogs. The shop I bought it from says nothing wrong with it.

WTF? Any ideas guys? I'm ready to go get a cheap corded one,(but I'll need 200 ft of cord)

edit: forgot to mention I don't squat about these type of carbs but ready to hear about jets and such

Make sure you have a new spark plug. My Stihl chainsaw seems lately to go through plugs as quick as my 911 can burn up a brazilian bosch coil. It gives weird running symptoms and then suddenly craps out. Lately- and maybe it's just me, the plugs just don't last. Everything else stihl... strong like ox.

On my "lesser" blowers, the diaphragms on the carbs get trashed by the ethanol gas. All they need to do is stretch ever so slightly. At least on the other brands- they don't even sell the gaskets, you just buy the whole carb to replace. Cheap pieces of crap.

edit- "lesser" brand = "TOY BUILT" I think also I have a "TORO" blower, but I can't remember. Ever since I bought "Stihl" Blower, weedeater, and Chainsaw... I have never looked back. Like they say, the most expensive tool you can buy is a cheap one since you will have to start over and replace it with a quality one later.

didn't think of the plug, I'll check that. tks!

Make sure choke is opening fully when warmed up.. Not sure which model you have, but some have a cold start position on the idle switch... You can run it without the airbox on and look inside the carb opening

another good one, thanks!

If it has a spark arrestor on it clean it. Brake cleaner works.

Yes, it's a screen between the exhaust port and muffler. Gets clogged. I bought a good John Deere weed-eater for $10 at a yard sale and that's the only reason it didn't run.

Also, if left sitting with fuel in it, clean the carb. Idle jet and pilot jet get clogged. The "bog" is a sign it's running lean and not getting fuel....G'luck....

Yep. They always do this when cold. If it does it when it's warm it's a sign of a lean mixture. ie restricted fuel flow.

Disclaimer: I'm not saying this is what it is. But it's worth a thought.

My Husqvarna weedeater was always a bit crappy. Then it went from bad to worse and I took it into the Husqvarna people for them to sort it. It was in and out of the shop about 3 or 4 times then they offered a big discount on another brand. I asked for one of their tuning screwdrivers and then found the shop's tuning was WAY out. Sure it doesn't idle but it's got way more revs, doesn't bog and die (just like your one is doing), and a LOT more power

Check the fuel line and return line for a obstruction. A buddy had a small piece of wood in his gas tank occasionally it would block one of the lines and cause running problems.

If you can, buy NO ALCOHOL premium gas. My small engines, 2 and 4 stroke both, run terribly on gasohol. Luckily, I can buy 92 octane no booze gas here...

Replace the carburetor

I have a bunch of Stil stuff...my weed eater is over 23 years old! Used it yeserday for over an hour. I do buy the Stil premixed, no alcohol, 93 octane gas at the dealer. Expensive but I've had no issues across the fleet since.

Check the primer bulb. They do deteriorate and can cause air leaks and "bog" at high revs.

Easy fix. I have a bag of them:cool:

Edit: FastFred is right. I have replaced carbs as well if the simple fixes don't work. Not worth the bug hunt. I just replaced one on a 25 year old mantis rotor-tiller: $45 online.

I am guessing it has one of those small Zama square carburetors. My buddy owns a husqvarna dealership. He says their success rate was low , with cleaning the carburetors on the smaller equipment. They even had an ultrasonic cleaner, just the, passages are super small, and sometimes impossible to clear out.
Ive had similar experiences . Had a few that I just could not make run right, even after several carb rebuilds. Bought new, and no problems . they are pretty cheap, usually only about $40

That's been my experience with 2 strokers. Once the carb. gets gummed up they will
generally start OK but won't take fuel unless running 1/2 choked. Never had any luck cleaning the carbs, just much easier to replace them.

and those square Zama carbs Fastfred mentions run $20-25 on the internet (or the last time I bought one anyway).

I haven't read all the replies but is it acting up on a full tank of fuel. These lines develop cracks and once the fuel level gets lower it can't pull fuel. Had this happen in a weed eater and a backpack blower. Also, the in tank fuel filter should probably be replaced if you're having a fuel issue.

happens on a full tank, new fuel filter, new fuel line(in the tank). lots of learning opportunities from youse guys, thanks much!

Sound like you are at the "replace the carburetor" stage. Before you replace it, take the old one off and check the gasket for leaks. It might be as simple as a loose carburetor or a bad gasket. Homelites had a flexible connection between the crankcase and the carb to minimize vibrating the carb.

I'm having the same problems flatbutt is ...I went the "replace carb" route . no bueno. Can't figure it out. If you figure it out, let us know!:)

Also replaced filter in tank and lines ...its something else

What about the coil? Mine idles fine ...

Try running it with the choke half on and see if it straightens out.

If it starts and idles fine but dies or almost dies when you give it fuel, I'm going with a fuel issue like a partially blocked main jet. As you're opening the throttle you're getting more air than fuel and going lean to a point where the engine dies or almost dies.

My experience: All of the remaining 2-stroke powered equipment being sold today are being tuned 'lean' from the factory to reduce emissions and smoke. That little carb has plastic 'limiters' on the mixture adjusting screws / low and high speed fuel circuits. Typically only allowing @1/2 turn either way.

They are installed by the factory to prevent 'Joe Consumer' from 'adjusting' the mixture out of range to the point of not running.

You are running lean on both. You'll need to first carefully turn counter-clockwise the low speed fuel mixture screw to the limit / limiter range. See if that cures the problem, because that is where you need it somewhat 'fat' when idling - so when you hit the throttle, the cylinder is loaded properly with fuel to accelerate as there is no accelerator pump shot.

If the mixture does not 'fatten' up enough - you can force it gently further by continued turning further which will break the limiter cap to get into the range you need.

Those screws should be clearly marked 'Lo' and 'Hi" - also do not confuse those with the idle speed screw which is a separate adjustment that does not have a limiter cap.

Any happy 2-stroke should emit a nice rolling, 'gurgling' sound at idle. Then instantly RPM when the throttle is hit WO. When held WOT and no load - there should also be a slight 'gurgling' that cleans up when a load is placed. If not, you'll need to adjust the 'Hi' speed mixture screw in the same way.

PM me with any questions past answered here if need be.

Yes, it's these I mentioned on my earlier post. The Husky people were trying to get it running to factory, low emission, spec's that just didn't work. I just turned them until it rev'ed like a, well like a small two stroke engine should.

Did you change the fuel tank vent? Try running it with the fuel cap loose.

Make sure you replace all the fuel lines with alcohol/ethanol resistant hose while you're at it. Cheap insurance.

2-stroke engines smoke, even when the fuel is mixed correctly. That means exhaust gasses and particles get, well, exhausted through the spark arrestor as is on most 2-stroke engines on yardequipment. So when you throttle up the combusted air/smoke cannot exit and the engine acts like it's not getting air when actually it is not exhausting it.

After checking fuel lines, gaskets, spark plug, carb, air/fuel adjustments, pure gas, blah blah blah and it still acts like it's starving for air------clean the arrestor.

Or clean it first and avoid doing all that other stuff.

If it still doesn't work, give it to your son-in-law to mess with and then throw out eventually.

Dump out your tank and start with all new fuel mix, fresh this week. Try running it without the air filter. Those new Stihl filters are made to clog. they won't blow out like the old ones would.

Mine was doing that. I took the carb apart and cleaned it up. Works fine now. I saw some yellowish looking build up in it from the crappy fuel we have now.

Turns out my brother was working on his friend's older Stihl BP blower that was having a similar issue. He cleaned the carb and adjusted and the thing ran fine for him but when his friend got it home it would run fine for a while and then start bogging down. His friend ended up buying a new blower. I almost wonder now if it might not be a coil issue were when it warms up from running it isn't losing resistance in the coil due to heat and then cutting out or not firing right?
I still think I'd try running it with the choke partly closed when it starts acting up to see if it clears. If it does clear that would indicate a lean situation meaning a plugged jet somewhere in the carb.

New carb on order.

When my Echo blower acts up and bogs down like your symptom a brand new fuel filter has fixed the issue.


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Keep us posted! I hope the new carb fixes it for you. I'm looking into buying some adjustment tools for my Husqvarna chainsaw, leaf blower and trimmer

Tks MB that was the first thing I checked, well the air filter first then the FF. Then following advice here I spent some time with the L and H screws but that didn't do anything. So I pulled the gas tank and the lines were "OK" but not great. Went on to the carb and found it to be ...well not to get too technical but it didn't look so very freakin' good. Ran over to my local chainsaw guy and he said the diaphragm was shot.

He also said that it looked like I had used old gas, which I had. He says that even if treated gasohol shouldn't be used if it's more than a month old. huh I didn't know that.