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Craftsman 4cycl leaf blowers runs poorly after warming up


lucius's Avatar
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11-25-16, 05:43 PM   #1  
Craftsman 4cycl leaf blowers runs poorly after warming up

Hi

Symptoms: Leaf blower runs for approximately 3 ~ 5 minutes, then runs sluggish once it's warmed up to the point it eventually shuts off. Will attempt to shut off if you attempt to full throttle.

Brand Craftmans (similar Troy Bilt models)
Model: 316.794610
leaf blower

Done the following:
- New gas
- New spark plug
- Cleaned air filter
- Cleaned out fuel lines
- Attempted to run w/o fuel filter - same issue
- Installed new carb
- Adjusted coil pack closer to flywheel

Please note:
- Will not run with clean air filter installed


Any thoughts on what my issue could be?

 
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cheese's Avatar
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11-25-16, 06:01 PM   #2  
Check the cylinder bolts to be sure the cylinder isn't loose. Does it run better with the gas cap loosened when it starts to mess up? Does the primer pump fuel easily?


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Wirepuller38's Avatar
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11-26-16, 05:52 AM   #3  
Blower

Clogged spark arrestor in muffler?????

 
Tony P.'s Avatar
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11-26-16, 07:27 AM   #4  
I go with the arrestor, too.

But also, you mention things you've done. Were any of them done before you had this issue. For example, I'm wondering if the spark plug was replaced properly.

 
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11-26-16, 10:12 AM   #5  
Thanks for the responses.


cheese,

The cylinder is secured just fine. The primer assembly works. As for the gas cap, it doesn't really have much of an affect on how the motor runs. It appears I can only run the motor at full throttle at 2/3 choke once the motor is warmed up. At some point it will run poorly then die out.

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Wirepuller38 and Tony,

I took apart the spark arrestor and it appears to be pretty clear.
Please see photo below. The spark plug was replaced with the correct one when this issue started happening.

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11-26-16, 12:16 PM   #6  
Does it spit back a lot of gas when you give it full throttle?


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11-26-16, 02:15 PM   #7  
It does not spit gas a lot of gas when I full throttle on any choke position.

 
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11-26-16, 04:56 PM   #8  
Does applying partial choke help keep it running? I'm beginning to think it could be a compression issue that is heat related or air leak.


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11-26-16, 07:58 PM   #9  
More than a partial choke keeps it running and I'm able to use full throttle. At some point the motor slow begins to fade in power then eventually turns off.

 
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11-26-16, 09:00 PM   #10  
Sure sounds like a carb or fuel line/filter issue but you've already eliminated those.


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11-26-16, 09:08 PM   #11  
Made any adjustments to the new carb?

 
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11-27-16, 06:23 AM   #12  
joecaption, I have not made any adjustments on the new carb. There are no adjustments that can me made other the the idle screw.

 
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11-29-16, 08:14 AM   #13  
Some progress has been made. I adjusted the rocker arms due to what appears to be a bit of play. The owner's manual states a clearance range between .003 ~ .006. I was able to slide a .008 feeler gauge between both intake and exhaust with slight resistance.

The new carb came with new fuel lines which I failed to install. I was only able to install primer line since the main filtered fuel line is too short.

Doubt this made a difference but I also swapped out the gas cap of one that is fully operational.

The small progress that was made is it stays running, I can give it full throttle (though I feel the power isn't 100% at full throttle). However, I will refuse to run with a brand new air filter.

A theory comes to mind....

Since it appears idle and 2/3 throttle just fine (despite not being to run w/ the air filter attached), perhaps it's starving for more fuel at full throttle. The filtered fuel line passes through a very tiny hole in the gas tank which may be constricting proper fuel flow right at the hole.

What I will attempt to do is run a fuel line, bypassing the fuel line hole and directly into the fuel tank.

 
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11-29-16, 06:04 PM   #14  
This happened on my Craftsman blower. I didn't have the tool to adjust the idle screws and found someone who did. Haven't had a problem since.

 
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11-29-16, 10:09 PM   #15  
This carburetor has no mixture adjustments. Not all carbs have adjustments.


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12-01-16, 03:47 PM   #16  
I bypassed the gas tank fuel line hole and ran a fuel line straight through the gas cap opening. It appears to run better; almost feels 100% full throttle.

However, it will attempt to die if I were to insert the brand new air filter. It will even attempt to die if I were to remove the air filter and just secure the air filter cap onto the carb. It will refuse to run with brand new air filter or just the air filter cap.

After running for a while even at full throttle, say approx 5 minutes of so, the performance will begin to deteriorate, eventually shut off and will not start.

Due to not starting, I immediately tested for spark with my testing tool and there was a good spark to jump the recommended gap range.

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At this point, I'm lost on what to test for next. New carb and it still having issues. Any additional advice will be greatly appreciated.

 
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12-01-16, 04:24 PM   #17  
How is the compression when it dies?


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12-01-16, 06:43 PM   #18  
When it starts to fade hit the primer bulb a couple of times. See if that will crutch it through.

 
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12-02-16, 05:09 AM   #19  
You have a lot of time and $ into this....maybe time to cut your losses and buy a new blower. I went through this replacing part after part....finally said too much time and $.....went out and bought a new one. It's admirable that you want to make it work and are doing everything you can but the leaves are falling.

 
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03-23-17, 07:50 PM   #20  
Re: Craftsman 4cycl leaf blowers runs poorly after warming up

We have a range of blowers to choose from and which one we select will depend substantially on how large a space we need to cover as well as other factors. That's why I only use my own leaf blower instead of using a more popular electric one.

 
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