Husqvarna 540xp Mk1 cuts out on idle

[Jon IOW]

Hi everyone, my 540xp Mk1 giving me problems, can't figure out why.

 

Symptoms are the idle is too low to keep the saw running, after 30 seconds or so at idle, revs gradually drop then it will cut out.

It will cut at full power, but a little sluggish to rev up to full speed.

Starts fairly easily.

Will do this behaviour regardless of hot or cold.

 

I've taken it to dealer, no error codes, latest firmware installed and reset Autotune.

 

Checked impulse line, looks okay, connected both ends. 

Compression feels strong, but giving 75psi which seems low. However, to compare I checked my 550xp (which runs lovely), and it gives the same, so maybe just my tester. 

Fuel and air filter both clean.

Replaced spark plug.

Primer bulb seems to work fine, pumps and refills nicely.

Given it a good run for 3-4 minutes at full power cutting to let Autotune do its thing.

 

Any other ideas? 

 

Frustrating cos its 90% there, just idle is not quite right and performance slightly sluggish. Like its being starved of air/fuel slightly.

 

Grateful for any advice!

 

Edited July 20 by Jon IOW

[Stubby]

Could be any number of things . Check the impuls line is still connected . 

[Mick Dempsey]

1 hour ago, Stubby said:

Could be any number of things . Check the impuls line is still connected . 

He has Stubs.

[Bolt]

Maybe it identifies as a 200t.

 

Have you tried launching it in frustration out of a really tall pine?

[Mark Bolam]

Memories!

[Dan Maynard]

If it's MK1 probably done some work, maybe worth taking exhaust off to check piston. Also carb rebuild, could be clogged somewhere.

 

Other thing spud says is sometimes people tell him the air filter is clean but actually there's oil and crud in the pores, so brake cleaner and airline to clean. Or fit new filter.

 

Probably a limit on how much worth spending though, isn't there? Whack it on eBay and buy a MK3.

[Stubby]

24 minutes ago, Dan Maynard said:

If it's MK1 probably done some work, maybe worth taking exhaust off to check piston. Also carb rebuild, could be clogged somewhere.

 

Other thing spud says is sometimes people tell him the air filter is clean but actually there's oil and crud in the pores, so brake cleaner and airline to clean. Or fit new filter.

 

Probably a limit on how much worth spending though, isn't there? Whack it on eBay and buy a MK3.

Also another thing Spud says is check the little gauze filter that is under a screw in the carb .,

[Jon IOW]

Thanks for comments.

Its 2020 so actually might be a Mk2? Cant remember if it was a mk1 or mk2 when I bought it.

 

Dismantled it this afternoon. Piston and liner look fairly clean, no significant scoring. Ring looks ok too.

 

Took the carb apart to clean it, also looks quite good and clean. No muck on the micro filter but cleaned it anyway.

 

Now I put it all back together I can only get a few puffs out of it, won't run at all.

 

Noticed there is a needle/screw on the carb behind the air filter holder. Looks like a idle speed screw or similar? I removed it to clean it out.  Just wondering if this is not set correct? Any ideas how many turns out from closed it should be?

 

I'm reluctant to bin it because its still clean and tidy, must be something simple.

[Stubby]

33 minutes ago, Jon IOW said:

Thanks for comments.

Its 2020 so actually might be a Mk2? Cant remember if it was a mk1 or mk2 when I bought it.

 

Dismantled it this afternoon. Piston and liner look fairly clean, no significant scoring. Ring looks ok too.

 

Took the carb apart to clean it, also looks quite good and clean. No muck on the micro filter but cleaned it anyway.

 

Now I put it all back together I can only get a few puffs out of it, won't run at all.

 

Noticed there is a needle/screw on the carb behind the air filter holder. Looks like a idle speed screw or similar? I removed it to clean it out.  Just wondering if this is not set correct? Any ideas how many turns out from closed it should be?

 

I'm reluctant to bin it because its still clean and tidy, must be something simple.

 

Edited July 20 by Stubby

[Stubby]

Just now, Stubby said:

Take it to your dealer and get it plugged in to diagnostics . Oh . I see you have done this as well .  Its a mystery .....