Husqvarna 125b issues

[Bounje]

Hi there,

I am trying to figure out what is going wrong with my 125b leaf blower. Any advice would be appreciated.

I was running it fine on Husqvarna 50:1 mix (I just mix the small bottle with 5 l gas as recommended) with premium fuel (stabilizer added to can right on pumping) and then I added a tank of Trufuel 50:1 premix in the hopes of cleaning the engine out a bit (maybe Moto Mix is better for this?). At that point I started to see issues. The engine started to run differently and I tried adjusting the carb. I went too low on the high speed adjuster and the engine just cut out and wouldn't start again.

At this point I cleaned the carburetor out with carb cleaner after taking it apart. The carb components appeared to be in decent condition with no bends or brittleness. I still ordered a rebuild kit anyways just to keep things in good order. I had already cleaned the spark arrestor a few weeks but checked it and the muffler again. There was no significant buildup behind it or on the spark arrestor. What I did notice was the piston had some black oil on it... I also checked the spark plug for spark and found it had some but didn't seem strong. However, it had oil fouling. So I cleaned it off and reinstalled it. New one is on the way. The engine started up and I adjusted the low and high speed carb screws until it was running well. Both seem to be on the faster side but I can't idle it with the idle speed too low or it cuts out. Do i need to adjust the Phillips idle screw more? I ran it for about 7 minutes full throttle and then it cut out. I was able to get it to restart and finished blowing the driveway off today (about 4-5 more minutes).

Is there enough information here to begin looking deeper into this problem? I ordered a compression tester and a multimeter but I don't know if these will be helpful to diagnose this issue.

 

[Rivets]

Are you adjusting the high and low fuel adjusting screws in the right order? I’ve always adjusted the high speed screw first. When it is running the way I want it, I adjust the idle speed screw so the engine is running to fast. Next I turn the idle speed screw out to slow the engine down until it starts to stumble. Now I adjust the idle mixture screw until it runs smoothly. Go back and adjust the idle speed screw again until it stumbles and then readjust the idle mixture screw until smooth. Keep doing this until I get the idle speed I want. Once I reach my desired idle speed I open the idle mixture screw about 1/8 turn. I do this to eliminate stumbling when I quickly open the throttle. Don’t know if this helps, but it’s worth a try.

 

[StarTech]

Really should be adjusting L first and then H as L interacts with H and not vica versa.

 

[StarTech]

Side Note> Standard carburetor cleaner should never be used to cube carburetors nor should high pressure air. There are delicate tiny (under 2 mm) rubber internal check valves which are damage by carburetor cleaners and high pressure air. Now Walbro does make specific carburetor cleaner for these but I just use soap and water in an Ultrasonic cleaner. Just watch out for loose welch plugs that may get shaken out.

 

[Rivets]

Then I must have been teaching and doing it wrong since the early 70’s. Manuals for Walbro, Tecumseh, and Briggs carb adjustment all indicate adjusting High speed mixture first, then idle mixture. This is because the idle circuit gets its fuel from the high speed circuit. If you adjust the idle circuit first, then high speed, you will be changing how much fuel is available for the idle circuit, so will then have to go back and adjust the idle mixture screw again. I’ve been using the procedure I posted forever and never have a problem.

 

[StarTech]

Then explain how H is affect L in the following diagram. I don't see where H is even supplying any fuel and I see no cross path either.


Here how fuel is flowing at full throttle.

 

[Rivets]

This is from Tecumseh manual for Tecumseh and Walbro carbs.

FINAL ADJUSTMENTS (NON EMISSION ENGINES)
Start the engine and allow it to warm up to normal operating temperature (3 - 5 minutes). Set the speed control to the HIGH or FAST position. From the recommended preset position, turn the main mixture adjustment screw in (clockwise) slowly until the engine begins to run erratic (lean). Note the position of the screw. Now, turn the screw out (counterclockwise) until the engine begins to run erratic (rich). Turn the screw in (clockwise) midway between these two positions. This will be the best setting. (diag. 24, 25 & 26).
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure used to adjust the main mixture adjustment screw.

Page 16 of this manual. https://www.mymowerparts.com/pdf/Te...P-4-CYCLE-L-HEAD-FLAT-HEAD-ENGINES-692509.pdf

 

[StarTech]

Two completely different carburetor designs for one thing but if you look closely at the idle and main paths of the diaphragm version they are two separate circuits.
Only float version has the main restricting the idle mixture path.


The diaphragm version has no such restriction.



Any way I do know the cubes are adjust L first then H when they have two separate adjustments or at least that is the way I have done it the last 13 yrs of working with the Walbro WT cubes.

 

[Rivets]

Not getting into a pi…..ing match over this. You do it your way, I’ll do it mine.

 

[StarTech]

Not getting into a pi…..ing match over this. You do it your way, I’ll do it mine.

That fine besides Tecumseh engines here a dead animal anyways. I only seen one in the last three years and it was toast as the parts were NLA. No rebuilding it. Ended up repowering with HFT engine.

Service manuals are only reference materials for me as I have numerous mistakes in them over the years. It like the time Victor told me it was impossible for an electronic calcuator to add wrong. I add 300 of them that did.