Husqvarna 545 rebuilt needs tweaking...?

[Lapsedout]

Hello fellas!
Firstly For all of the conversations I read in the past weeks helped me rebuild my first chainsaw, but ...!

it’s a small but, ie: after rebuild which is :
-top cover opening for better cooling
-muffler drilling for slightly better exhaust flow
-spark plug gaping
-side transfer port sealing
-air filter cleaning
-air filter mount sealing
-air filter mount cleaning ( blackish oil’s residue)
-autotune cleaning ( little magnets)
-autotune wire testing for continuity
-carburetor heat shield improvement ( thermal tape front and back )
-carburetor cleaning ( ports only )
-carburetor assembly screw check
-carburetor hiden adjustment screw 1/4 or close to...CCW
-cylinder swap for a 550xp
-piston cleaning ( initial exhaust side scoring)
-oem piston ring
-new sprocket rim
-tons of cleaning and lube and grease
-new bar and chain ( 18 Oregon speed cut combo )

... it started well, on idle never stalled and while idling I did a thorough leak test with carb cleaner and it was all clear ! Revs wot pretty responsively ( yes it screams like a huskies). BUT yesterday I went to a friends place to cut a few logs and it went amazingly.
From my home logger friends point of view the saw was good ! Then my turn came around to experience the cutting ( saw was warmed up ) and boom it dies ! No worries it didn’t literally go BOOM it just stopped BUT why ? I restarted the saw from one pull and set my self up to cut and dies again ! WTH ! Started it up again one pull of the cord and let it idle... after a minute looking at it idle I pick it up and ever so slightly I touch the throttle ( 1 or 2 % of the full throttle spectrum ) and it dies again. So if my trigger finger twitches it dies but if I pass trough that part of the throttle fast enough it respond’s instantly.

I’m thinking a little more of that hidden screw might do it !

I’m open to your thoughts fellas !

Context of the saw prior to rebuild was
-My uncles saw since 2015
-always had issues with it not idling and bogging on wot or up revs
-after 5 years of neglect and poor maintenance and abusive usage ( extreme heat blueing on old chain bar ) it suffered from the said piston and cylinder scoring on exhaust side.

 

[Fullkip]

Before going any farther do a leak down test. Have carb checked for any codes. Pull muffler and check for any tranfer/scoring...

My ported 550s run well with the hidden carb screw 1.25 turns out.

 

[Lapsedout]

Hi, 1&1/4 turn out from completely seated adjustment screw ? I ran the saw again this morning, in my backyard and in the city ! My buddy let me take home a two foot log for further testing.
And strangely it didn’t die out after poking the trigger as mentioned before. But one thing I noticed before taking it out is a mini split in that S shaped primer bulb gas line. So I instantly replaced it with proper size gas line until I can order a new one. I did pull muffler out all is ok inside. The saw ran flawlessly so next in line of thinking is carburetor update. Should I do it nonetheless or leave it as is ( 2015 saw with Walbro AT7A carb )? With out being 100% sure it probably has never been updated since 2015. The only comparable way of a leak down test I did is spraying carburetor cleaner around all the seals intake and crankcase and no reaction from the saw at all.
Thks for the input

 

[Fullkip]

Sounds like you found the issue good catch.
If it still gives you run issues have a full pressure and vacuum test done on the fuel system. The main nozzle in the carb can fail at times. You might also try the new husky fuel filter.

 

[kneedeepinsaws]

I think stock was 3/4 out from seated if i remember correctly.
When i had mine i believe i had it set at 1.25 or 1 turn out from seated.

I dont miss the 550 after reading this thread!!!

 

[Lapsedout]

Thks actually mine is a 545 but I was lucky enough to find a good used original 550 cylinder to rebuild my 545. Btw I can’t explain why but both cylinder had the same part number cast in them but the 550 had a hollow section in the upper part of the exhaust port ( top ) in the casting. The rest of the part seemed identical. I’ll update soon on the idle bleed screw setting. Most likely when this confinement period is over here ( Quebec prime minister shut down all non essential business till Jan 11 ) I’ll get the carburetor updated and see if any codes are stored
Thks

 

[Fullkip]

The newer 550 and 562s have the trough on the exhaust roof. I haven't checked port timing on OE versus NE cylinders. 572s also have them...
The troughs are a pain to deal with when porting. Some get a bleed over plating...

 

[Lapsedout]

So it’s made to help the exhaust get out faster or have more exhaust volume escaping the cylinder?

 

[Fullkip]

It's all about getting a cleaner burn, EPA stuff .. I think it would interrupt flow... Check out inside the mufflers...

 

[Lapsedout]

It's all about getting a cleaner burn, EPA stuff .. I think it would interrupt flow... Check out inside the mufflers...

Is there a specific color inside the muffler to look for ? Mine is on the sooty grey color. Having that said , by increasing the flow of exhaust by drilling extra holes under the spark screen, will I notice any performance difference apart from a bit of extra noise?

 

[Fullkip]

I gut the mufflers I do, seems to help with torque. The main reason to gut them is to get rid of heat. The gutted ones with the extra side port aren't as loud as the ungutted single port that has been opened on inlet and outlet sides. Not the piped ones...
Gray to tan screens are what you want. I like a light tan on plug and screen. If your auto tune saw has a dark or white screen pull out of service. Check codes, leak down test...

 

[Lapsedout]

Awesome. I appreciate the information. I’ll keep those in mind.