Husqvarna 350BT

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  #1  
Old 07-20-15, 08:55 AM
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Husqvarna 350BT

I have a Husqvarna 350BT leaf blower (backpack style) that is 3 months old and it has slowly developed a problem where it loses power whenever I give it more throttle.

I've checked the fuel and even purchased some pre-mixed 92 octane 50:1 without any change in performance. Yesterday, I tried the following:
removed the fuel filter (it's attached to the fuel line in the tank, so removing it was easy)
removed the fuel line from the carb and let it drain
removed the other fuel line (I'm guessing it's some kind of thing to overcome vacuum issues?)
tried running it with the fuel cap off
removed the spark plug and had a guy from AutoZone look at it. We both thought it looked fine from what we could tell. Light tan color.
removed the air cleaner
inspected the areas where the carb mounts to the engine - gasket looks good and seems tight/normal.

After each of the above changes, I tried starting it to see if there were any differences.

When I had the air filter off, I also squirted in some carb cleaner.

To me, it seems like it's a fuel problem, and since it has new fuel, it seems like it isn't getting enough.

When I increase the throttle, it will respond appropriately momentarily and then almost die. When I do it more slowly and then decrease throttle, there is some pinging/knocking going on. Don't know what that means.

Finally, when I first bought and used this, it worked like a champ. I used fresh gas mixed with 50:1.

I'll also add that I have been getting similar problems with other small engines. I have another Husqvarna leaf blower that is handheld. It recently had an overhaul and then very quickly it experienced the same symptoms even though I was using good fuel. That's actually what prompted to me purchase this new one. I have a wood chipper form Sears that usually runs like a champ. It's 4 stroke, so no mixing. It will run at full throttle, but when it's under load, it quickly loses power.

Any chance it can be an ethanol issue? I've never had small engine problems like these before....
 
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  #2  
Old 07-20-15, 09:12 AM
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Since you're seeing it in a number of engines using the same fuel type and source, that would be the place to start. You can usually get non ethanol fuel so do that, Also if you're storing it for a period of time, get fresh fuel and get rid of any old fuel you have.
 
  #3  
Old 07-20-15, 09:43 AM
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I had that thought as well, which is why I bought some premixed non-ethanol fuel. What I don't know is if some bad source fuel (even if it's fresh) can cause other problems to the motor that remain even after switching fuel.
 
  #4  
Old 07-20-15, 10:37 AM
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You could easily have gotten some bad fuel that plugged up the carbs and/or filters. Assuming it was varnish causing the problem, Sea Foam would likely take care of it in short order. If the filters were plugged with dirt solids, those would have to be changed.

As long as you had the oil in the mix and the engine would burn it, it's unlikely any damage to the motor was done. Everything was probably confined to the fuel system. And those are the symptoms you're seeing.
 
  #5  
Old 07-20-15, 11:41 AM
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I'll try the Sea Foam ASAP and hopefully that works. Thanks for the suggestion.
 
  #6  
Old 07-20-15, 12:02 PM
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Blower

Check the spark arrestor screen in the muffler. Could be clogged.
 
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Old 07-23-15, 09:10 AM
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I tried the Sea Foam last night. I first added some to the fuel and let it run. No improvement. I then added some into the carb while it was running and let it run for a bit. There was some improvement after that, which was encouraging.

I then turned it off and put some more into the carb and cranked the engine over a touch hoping some would get into the cylinder and let it soak overnight.

I just fired it up and let it run for a few minutes. There is a definite improvement, but not back yet to full power. When increase the throttle, it responds well up until about the 75% area, but this is much, much better than before.

I'm going to let it idle for 5 or ten minutes, see if there is any improvement, and then probably let it soak again overnight.
 
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Old 07-23-15, 01:48 PM
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What do you have for mixture adjustment screws on the carb? Are there two, marked "H" and "L" or just one.

Usually when the passage in the carb is passing some fuel, the Sea Foam will clean it out right away. If there is a complete blockage the Sea Foam has to work its way through it would take longer. That's where a dismantle and clean would speed up the process.

If you double the dosage of Sea Foam, run it for a couple minutes to get it into the carb, then choke the carb to kill the engine, it will move the cleaner through things pretty well.

What you're describing as far as what you're doing and the results would indicate you may have an exhaust screen blockage or a pulse port blockage that drives the pump in the carb. Those are the only two places the cleaner put directly into the carb throat would affect. There is a chance, though the cleaner in the gas is working its way through the carb cleaning some tough blockages.
 

Last edited by marbobj; 07-23-15 at 02:03 PM.
  #9  
Old 07-23-15, 02:25 PM
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I added more Sea Foam to the cylinder by removing the plug and just dumping it in there. Let it sit a few hours. After starting it, I ran it for a few minutes and it's working much better now. I can finally give it full throttle without it dying, but it's still not quite full strength but probably in the 90% range.

Next, I'll check the exhaust screen but I needed to let it cool down. I'll try that tonight.

Also, when I give it full throttle, it gets a bit weak but then grows stronger, which makes me wonder if it's not an exhaust problem.

I also figured that by using it for a half hour or so, the Sea Foam in the current fuel can keep working on it.
 
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Old 07-23-15, 03:30 PM
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When you put it directly into the plug hole two things that will clean are the exhaust screen and the pulse port. It still doesn't explain the problems you've had with the 4 stroke. It could have just been some really bad fuel that got all your machines plugged up - carbs/filters/screens. The screen is pretty easy to check. You might want to just manually clean that and let the Sea Foam do the work on the 4 stroke.
 
  #11  
Old 07-23-15, 03:47 PM
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I haven't tried anything on the 4 stroke yet, just the leaf blower. I use the leaf blower every week and the 4 stroke only occasionally. I'm thinking it was either a bad batch of gas or too much ethanol or a combination of both. I always treat the gas for these yard tools but I guess it could still go bad.

The weird thing about the leaf blower, however, is that it's new and I bought it this spring. The gas has always been pretty fresh. That's what makes me wonder if it was an ethanol issue.
 
  #12  
Old 07-28-15, 05:20 AM
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I checked the spark arrestor and it looked fine. The motor is still lacking power. It's better than before, but will only maintain power up to about 75%. The knocking/pinging is mostly gone. Still using the special pre-mixed non-ethanol fuel.

Any thoughts? Might this work its way out through use with Sea Foam, or is it time to look at something else?
 
  #13  
Old 07-28-15, 10:07 AM
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Running it lean like this is going to score the piston and stick the ring. Check the carburetor for two small screws side-by-side. They might have plastic limiter caps over them or they might be recessed where you can't get a tool on them to open them. If you find them, the one closest to the air filter side of the carb is the high speed screw. Try backing it out 1/8 turn or so and see if it improves.
 
  #14  
Old 07-28-15, 12:33 PM
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The Sea Foam will normally work its wonders in a short time. Some users add a little for a regular maintenance.

Port designed two strokes are really pretty simple as to what goes wrong. For air flow problems it's usually the exhaust screen or air filter, then seals or gasket leakage. Then fuel problems from either carbs getting gunked or diaphragms becoming stiff with age. Then compression with cylinder scoring. Finally ignition with coil and spark plug, and kill switch.

Normally, performance levels, for the average user, aren't affected too much by compression or ignition. If you can get it started you're over half way home. Performance is more related to air flow and carburetion/fuel problems. The latter would include seals and gaskets since those can haul in a host of problems with fuel/air mixtures.

Have you tried to adjust the fuel/air with mixture screws on the carb and what is it outfitted with? Some just have one and others have a pair - one high speed and one low speed. Once a carb is cleaned up that's where you would go to fine tune it. On a new machine they shouldn't need a lot.
 
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