550XP, new A-12 carb? Where to get one, how to match coil?

[Brent Nowell]

If the saw doesn't have an air leak, just bite the bullet and get a new carb. I think they're a few reputable sellers on eBay that will program the carb to the coil.[emoji111] Don't expect the saw to ever start perfectly when really warm, that's just not going to happen, at least it hasn't in my experience.

Wow, every other saw I have can lol
So I guess my expectations are too high lol
Sigh... what a pile this thing is turning into.

I appreciate your feedback by the way, I’m just whining.
Brought it to the dealer, the guy who does it wasn’t in... so i ask why no one else can and I’m given this story about how it’s a big technical training session... then they said that I’d have to book it in anyways and wouldn’t get it back same day..

Well now I got mad and said that it takes literally minutes to do, there’s no reason why it has to take more than a day. Also bitched about how I have to pay to update MY saw, I also mentioned that you can’t change any settings, you can only view them. So why is training needed lol?? You plug it in you can upload firmware, or you can look at how the saw is running, that’s it. They just said that only one guy can do it... I bitched some more about this and that and finally they said I should talk to husky and gave me a phone number. So that was that, went home and ripped apart the saw.

Did my first test on the tank vent and looks like it holds a bit of vacuum and pressure.. the pressure I can understand, increase pressure slightly and you prevent gas from leaking out and you increase the boiling point for hot starts. However the fact that it held some vacuum was concerning, probably just enough to cause some starvation issues...

I know there’s an updated part number for the vent, but does anyone have a pic of the new one? I’d like to see if I have it or not

A pic is attached

 

[Brent Nowell]

Also Andy I want to fully test the carb before I replace it or have you seen issues with the auto tune unit attached to the carb warranting to replace it?

 

[Brent Nowell]

cleaned tank vent as best I could,

Found a discrepancy with the carb in which the needle arm is above level with the body of carb. The service manual says this is a no go, and it must be level. I used a straight edge.

Vacuum test failed on the purge nipple, not sure why but looks like this carb was assembled wrong

 

[Andyshine77]

Also Andy I want to fully test the carb before I replace it or have you seen issues with the auto tune unit attached to the carb warranting to replace it?

The AT it's self seem to be ok as mentioned previously, the carbs are junk.

 

[Brent Nowell]

Well it’s now fully assembled, leak down test passed at ten minutes of pressure and vacuum each.
Carb metering lever was adjusted to be flush with carb body, it was originally out by almost an 1/8”
I adjusted the screw back to its 3/4 turns out stock position. I am fairly convinced with the metering arm too high all circuits were rich especially idle. I believe the saw could not compensate for this with the AT module, and thus opening the air screw more worked for idle. With the arm back to normal it should be seeing the proper fuel amount at all rpm ranges and thus the auto tune adjusting valves will now be in scope of this proper fuel amount... again that’s what I’m thinking here, truth is gonna be in the next couple hours.

Tank vent was partially clogged and now seems good.

I’m really curious to see if these “junk” carbs really are just carbs that did poor on the quality control. Are the carbs that do not work properly just out of adjustment in terms of the metering diaphragm arm? If anyone has an old one that worked like crap you should pull off the metering diaphragm plate and check the arm with a straight edge.


I’m just waiting for sealant to dry and I’ll see how it runs, hopefully the service manual is correct on the arm lever height

 

[CenterTree]

...., truth is gonna be in the next couple hours. ...



I’m just waiting for sealant to dry and I’ll see how it runs, hopefully the service manual is correct on the arm lever height

Any luck?

 

[Brent Nowell]

Any luck?

Yes the luck is good, so far
I started it last night and it started right up and ran good. Some bogging on low end to accommodate the new fuel volume I would think and it then cleared right up. I shut it off and had it idle for two minutes straight with no rpms lower than 2600. So this is actually working as before with the idle air screw out 3/4 it would stall, every time.

I started it just now and it started right up, again blipped the throttle as fast as I could and throttle response is there. Keep in mind my linkage arm is now bent to sync primary and secondary butterfly.
I again let it idle for a few minutes and again the tac showed nothing less than 2600.

I can’t hit wood yet and reset it, so that will have to wait for the weekend.

I am confident that anyone with carb issues try this as with the metering arm adjustment as per the service manual on the at-12 carb does work!

I will keep this posted as I know there are other frustrated 550 owners like me

 

[superwd6]

Yes the luck is good, so far
I started it last night and it started right up and ran good. Some bogging on low end to accommodate the new fuel volume I would think and it then cleared right up. I shut it off and had it idle for two minutes straight with no rpms lower than 2600. So this is actually working as before with the idle air screw out 3/4 it would stall, every time.

I started it just now and it started right up, again blipped the throttle as fast as I could and throttle response is there. Keep in mind my linkage arm is now bent to sync primary and secondary butterfly.
I again let it idle for a few minutes and again the tac showed nothing less than 2600.

I can’t hit wood yet and reset it, so that will have to wait for the weekend.

I am confident that anyone with carb issues try this as with the metering arm adjustment as per the service manual on the at-12 carb does work!

I will keep this posted as I know there are other frustrated 550 owners like me

Done exactly the same lever adjustment on mine a couple weeks ago. Been to 2 different dealers and seemed ok after last computer update. Most of my cutting is in cold temps but lately I it started its bog if idled more than 10 seconds like when new .Idle for a minute would blow black smoke lol. Set my inlet lever level as per manual and now perfection. Timed hot running saw after half tank,idling over 3 minutes hit throttle to 0 hesitation then finished the complete tank of fuel with no issues. When saw was new it seemed to start bog at about half a tank making me think bad fuel line or filter hanging up.. will be running saw again soon to see if I buy another Husqvarna or move on lol
Hidden air screw done nothing for mine [emoji849][emoji23]

 

[Brent Nowell]

Interesting. Sounds seriously like clogged tank vent, at least partially. They have lots of resistance when clogged, when you spray it out with carb cleaner and an air gun and hook up the vac test to it you will see the difference. It goes from actually holding a little vacuum and pressure to holding zero after the clean.
It’s almost like these tank vents have too much resistance even when clean...

Well I know for a fact that I have no air leaks, and the tank vent is not clogged so all that’s left in this experiment is some hard unforgiving work to see how it rolls...
either way your input adds to the data in a way, thank you

 

[Andyshine77]

Well it’s now fully assembled, leak down test passed at ten minutes of pressure and vacuum each.
Carb metering lever was adjusted to be flush with carb body, it was originally out by almost an 1/8”
I adjusted the screw back to its 3/4 turns out stock position. I am fairly convinced with the metering arm too high all circuits were rich especially idle. I believe the saw could not compensate for this with the AT module, and thus opening the air screw more worked for idle. With the arm back to normal it should be seeing the proper fuel amount at all rpm ranges and thus the auto tune adjusting valves will now be in scope of this proper fuel amount... again that’s what I’m thinking here, truth is gonna be in the next couple hours.

Tank vent was partially clogged and now seems good.

I’m really curious to see if these “junk” carbs really are just carbs that did poor on the quality control. Are the carbs that do not work properly just out of adjustment in terms of the metering diaphragm arm? If anyone has an old one that worked like crap you should pull off the metering diaphragm plate and check the arm with a straight edge.


I’m just waiting for sealant to dry and I’ll see how it runs, hopefully the service manual is correct on the arm lever height

More are bad than not. I have gone through a few of them now, adjust bleed screw, meetering lever height, played with pop off pressure, opened up the throttle butterfly. Sometimes it will get a saw right, mostly not. Sometimes the 562 would take to opening up the throttle butterfly and resolve the off idle stumble, this was awhile back, that issue was resolved years ago.

Run the saw for a tank or two and see how it goes, as that's when I start seeing issues rear their ugly head.

 

[Brent Nowell]

More are bad than not. I have gone through a few of them now, adjust bleed screw, meetering lever height, played with pop off pressure, opened up the throttle butterfly. Sometimes it will get a saw right, mostly not. Sometimes the 562 would take to opening up the throttle butterfly and resolve the off idle stumble, this was awhile back, that issue was resolved years ago.

Run the saw for a tank or two and see how it goes, as that's when I start seeing issues rear their ugly head.

Again thx for your input. Sounds like this is probably not going to work..

I’ll probably call my stealership and see how much a new one costs... just so I can get a ballpark

 

[Andyshine77]

Again thx for your input. Sounds like this is probably not going to work..

I’ll probably call my stealership and see how much a new one costs... just so I can get a ballpark

Well I'd at least give her a go before buying a $100 carb, it may very well work just fine now, only one way to find out.

 

[Brent Nowell]

Yes those were my intentions to try it out first. I’d love to hear what all youve done to these saws to get them to work

 

[Andyshine77]

Yes those were my intentions to try it out first. I’d love to hear what all youve done to these saws to get them to work

After getting the carbs shorted out, heat is the next thing to deal with. A good muffler mod, heat shielding, delete the decompression valve "this helps starting" and sometimes adding vent holes in the top cover around the carb area. Good fuel @ mix 40:1 Also letting AT saws idle too much messes with the settings, as does running the saw out of fuel. Reading them a bedtime story and tucking them in at night helps too.[emoji16]

 

[Brent Nowell]

After getting the carbs shorted out, heat is the next thing to deal with. A good muffler mod, heat shielding, delete the decompression valve "this helps starting" and sometimes adding vent holes in the top cover around the carb area. Good fuel @ mix 40:1 Also letting AT saws idle too much messes with the settings, as does running the saw out of fuel. Reading them a bedtime story and tucking them in at night helps too.[emoji16]

I know right? Gotta baby the stupid thing it feels like!

Did you find that buying a new carb cured your running/bogging issues?

Have you found that buying a new carb actually came defective and you had to buy another?

 

[Brent Nowell]

Just an update on the lever arm adjustment

The saw will idle no prob now with the adjustment made and the stock bleed screw setting.

I have tested the saw now twice for long periods each time.

Saw still bogs when first starting, it really is a chore to get the auto tune to get used to the temp changes... once it has adjusted the saw will run great with no bogging.
I did a lever arm mod on this saw and I’m starting to think that the auto tune cannot adjust to this properly. Gonna put it back to stock and put a stock muffler back on at some point, and try again...

 

[Kmoss]

Saw is a 2014 550XP. I think it has the A1 carb. I need a source for the newest A12 carb (which I can get at Bailey's), but I would need to have it matched to my coil. (Bailey's is not able to do that). My dealer is incompetent and also not an option. A 2nd dealer is 25 miles away.

Anyone here who can ship me a brand new A12 that is already programmed to my coil if I provide the info?
I hope to be able to try and revive this Husky blunder before I drop big bucks on a new Mark 2.

Thanks!

Can you tell me what the part number is for the new carb at-12? I’m to completely replace it like this guy did in this video on YouTube. It’s the exact problem we are having with our 550XP 2014



looking for complete replacement not a rebuild kit also would like the genuine Husqvarna number if anyone has it

thanks

Katie

 

[DND 9000]

Part no. for the carburetor AT-12 is 587 08 48-06. But go to your dealer and let him do the swap. You can`t do it by yourself, it will not work. The autotune unit has to be flashed with the right firmware.

 

[Kmoss]

Thank you so much

 

[Andyshine77]

Actually if you take the module off the old carb and put it on the new carb it may work, it has worked for quite a few guys. If not the new module will have to be programmed as it's blank from the factory.