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150BT backpack blower

#1

O

Oddjob

I am stumped. The blower starts easily and runs well for 5-10 minutes then bogs down under full throttle. I replaced the fuel filter assuming it was a fuel starvation issue. Didn’t solve it. I had an extra carb so switched it out. Same exact symptoms persisted. Tried adjusting the mixture screw, no difference. Changed the sparkplug, no difference. I put an inline spark detector on and ran it. Showed spark when it bogged down but not as bright, so installed a new coil. Same symptoms. The fuel is fresh. The air filter is clean, almost brand new. Tried running it with the fuel cap loose and it still bogged down after a few minutes. Nothing has worked so far. Could the fuel line be collapsing? Anyone have any ideas? BTW, this has the newer carburetor.


#2

R

Rivets

Could be a plugged spark arrester, muffler, or exhaust port, check these first. Remove the muffler and try running to see if there is any change. Yes it is going to be loud.


#3

O

Oddjob

Thx Rivets, will try that tomorrow at a decent hour. I forgot to post that I had checked the spark arrester screen. It was clean.

If the muffler gets eliminated as a cause, could there be something internal in the carb that would cause this, like a failing diaphragm? I can’t understand how a diaphragm would be ok for ten minutes and then quit. If it was bad, I would think that it wouldn’t pump from the start.


#4

Tiger Small Engine

Tiger Small Engine

Oddjob said:
Thx Rivets, will try that tomorrow at a decent hour. I forgot to post that I had checked the spark arrester screen. It was clean.

If the muffler gets eliminated as a cause, could there be something internal in the carb that would cause this, like a failing diaphragm? I can’t understand how a diaphragm would be ok for ten minutes and then quit. If it was bad, I would think that it wouldn’t pump from the start.
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If the blower is getting up to speed fine, then it is not the spark arrestor.

You have replaced a lot of parts. Are the replacements OEM or aftermarket? How old is it?


#5

B

bodean

I had this problem on my old chainsaw. After lots of aggravation , I discovered that the ends of the fuel lines weren’t fitting as tight as they once were, and was allowing tiny air bubbles to enter the line at full throttle. I replaced both fuel lines with high quality ethanol resistant lines and problem solved.


#6

O

Oddjob

Tiger Small Engine said:
If the blower is getting up to speed fine, then it is not the spark arrestor.

You have replaced a lot of parts. Are the replacements OEM or aftermarket? How old is it?
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I think it is a 2022 model based on the appearance of the carburetor and what my daughter-in-law thought she remembered about when she bought it. The serial no. is 20223302062 but I couldn’t find a definitive way to read Husqvarna serial numbers for year of manufacture. One source said that Husqvarna uses the first two digits for year of manufacture but I am pretty sure it is not a 2020 model.

The filters are aftermarket. The spark plug was oem, the replacement was aftermarket. The carb that is on there now is the oem carb that I removed a year and a half ago when I had replaced crumbling fuel lines. The fuel line is what came with the aftermarket carb.


#7

StarTech

StarTech

11 digit serial numbers
First 4 is year.
Next 2 is the week of the year.
The last five digits show the sequential production number (e.g., 00362 indicates the unit was number 362 in production order that week).


#8

O

Oddjob

StarTech said:
11 digit serial numbers
First 4 is year.
Next 2 is the week of the year.
The last five digits show the sequential production number (e.g., 00362 indicates the unit was number 362 in production order that week).
Click to expand...
Thx.


#9

O

Oddjob

I think I solved it. I had been thinking that it was a fuel starvation issue but I was wrong by 180 degrees. It was running too rich.

This carb has just one adjusting screw. I reset it to the factory setting and the blower started easily and ran well. Then it began to bog down again, so I tried giving it more fuel via the priming bulb. That made things worse, but it gave me an idea that the problem may be too much fuel rather than not enough. Because it ran well at start-up at the factory setting I didn’t think that it needed much adjusting. I was wrong. I leaned it out and it really came to life and it stopped bogging down when fully warmed up. The factory setting was 1 1/4 to 1 1/2 turns. My final setting after backing it off from peak power was a tad less than one turn.


#10

StarTech

StarTech

Even factory setting are sometimes just a will start setting.


#11

Tiger Small Engine

Tiger Small Engine

Oddjob said:
I think I solved it. I had been thinking that it was a fuel starvation issue but I was wrong by 180 degrees. It was running too rich.

This carb has just one adjusting screw. I reset it to the factory setting and the blower started easily and ran well. Then it began to bog down again, so I tried giving it more fuel via the priming bulb. That made things worse, but it gave me an idea that the problem may be too much fuel rather than not enough. Because it ran well at start-up at the factory setting I didn’t think that it needed much adjusting. I was wrong. I leaned it out and it really came to life and it stopped bogging down when fully warmed up. The factory setting was 1 1/4 to 1 1/2 turns. My final setting after backing it off from peak power was a tad less than one turn.
Click to expand...
It is amazing on handheld equipment how small adjustments on high and low mixture screws can affect the performance. On small engines, the carburetor set up correctly and having the air/fuel mixture is crucial.


#12

StarTech

StarTech

This why a tach is very useful in adjusting these carbs. Most are usually tune to peak power and then enriched to slow down around 50-100 rpms and this is done after the unit is warmed up a bit. Tuning by ear just doesn't work here.


#13

O

Oddjob

StarTech said:
This why a tach is very useful in adjusting these carbs. Most are usually tune to peak power and then enriched to slow down around 50-100 rpms and this is done after the unit is warmed up a bit. Tuning by ear just doesn't work here.
Click to expand...
Can you recommend a particular tach?


#14

StarTech

StarTech

Tiny Tach II is one but I am currently using one from Husqvarna that will shutoff the screen when not in use as to extend the internal battery life which is not replaceable. Both are good up to 20,000 rpms.

I prefer the direct induction type over the wireless ones. Plenty of copy cats tachs out there too that would work well. Just make sure you read the reviews especially the bad ones.


#15

O

Oddjob

Thx.


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