Husqvarna 455 Surging at Idle, Air Leak or Carburetor Problem?

[dsell]

I'm working on a 455 and it runs fine at full throttle, starts in one pull, but occasionally runs away at idle. It's difficult to adjust the low side, but I'm not familiar with this system. The caps have been pulled, what is the factory setting on the low needle? The fuel lines are fine and I just had the carb out because it was missing the choke plate and screw that connects the pull. Do I need to rebuild the carb or do an air test? Is there a common air leak that occurs on this model? Compression is 155, good spark, cleared the spark screen, and the cylinder wall looks good on the exhaust side. Didn't pull the muffler. Hoping to gain some tips from someone with experience on this model.

 

[jdvsn83]

Those kind of problems are very common within modern husqvarna saws, at least in the configuration Husqvarna sells in my country...

Some of them have an accelerator pump with a tiny o-ring behind their throttle shaft and they develop an air leak. It's perfectly fixable overriding the system just like on Stihl 192T and similar models.

The other ones show air leaks when hot and I think those symptoms ar related to compression loss or seals leaks when temperature raises.

Common air leaks for 455 and similar Husqvarna models are: Crank seals, cylinder to seals contact, cylinder base gasket, transfer caps, intake system and impulse line.

They're a pain in the ass to fix when they start to show those problems...

 

[dsell]

I took it out the next day, tuned it a bit, and it never ran away. I ran it for an hour, mostly idling, and it never took off. I'd rev it every now and then and it always come back to idle like it should. It's a ghost that I'm sure will come back.

 

[jdvsn83]

I took it out the next day, tuned it a bit, and it never ran away. I ran it for an hour, mostly idling, and it never took off. I'd rev it every now and then and it always come back to idle like it should. It's a ghost that I'm sure will come back.

I'm having the same issue with a 235 in my shop. A few days ago it would not idle. Today it runs like a charm... Pressure and vacuum tested the crankcase and every part, new gaskets, carb kit, lines, filters, tank vent, etc.

They usually show erratic idle when hot. Maybe they have a cylinder internal problem... I can tell you these husqvarnas and some poulans are the few saws you won't find the real problem...

 

[Jackbnimble]

I wish I had a clue what to tell you. My MS 660 decided to play hard to get, too. She'll start for me and run like a champ. But when it's time to give her fresh fuel, she doesn't like to fire up again and get back to work. She takes long siestas. Acts like she's retiring for good. Though, if I wait a day, she jumps at the chance to chew away vast amounts of wood.

 

[dsell]

I wish I had a clue what to tell you. My MS 660 decided to play hard to get, too. She'll start for me and run like a champ. But when it's time to give her fresh fuel, she doesn't like to fire up again and get back to work. She takes long siestas. Acts like she's retiring for good. Though, if I wait a day, she jumps at the chance to chew away vast amounts of wood.

That's very aggravating and expensive to throw parts at.

 

[Ozhoo]

Flex the AV system and see what happens. While it's cutting, lean into it to compress the intake manifold. Then do the opposite to expand the manifold, do an up cut while pulling up as much as you're comfortable.

 

[Jackbnimble]

That's very aggravating and expensive to throw parts at.

Well, the good news is that today she decided to be a sweetie and cooperated like she wants something for her birthday.

 

[Jackbnimble]

Well, the good news is that today she decided to be a sweetie and cooperated like she wants something for her birthday.

I gotta say, when she, the MS 660 is in a good mood, she's a trip to use. She's a land mine, a portable nuke, an M1A2 Abrams. I love cutting wood with that animal. Love it. Can't wait for tomorrow.