Husqvarna 550XP intermittent power mystery.

[pleasant]

Appreciate the feedback OP

[Guest Gimlet]

Mine's been doing a similar thing. OK for 15-20 minutes then starts to bog and won't rev and makes an odd rasping noise from the exhaust. I took it to a dealer who stripped it and said the diaphragms were full of a milky substance. He cleaned it and it was fine for a couple of days, then the problem returned. I'd changed the fuel in case there was water in it but it made no difference and my old-school 365 was running perfectly on the same batch fuel. It sounds like water or an air leak within the saw may be causing fuel emulsification. 

 

I hate the thing. Wish I'd bought an older used saw and refurbed it. The 550 has been nothing but trouble from day one.

[butters]

Will be the coil. I’ve got 2 550’s that are in all the time for new coils. 
 

according to the dealer husqvarna have changed the part number for the coil so hopefully they have fixed the issues. One saw I’ve had has gone through 3 coils in 9 months. 
 

amazing saws when working but getting tired of coil issues now. 

[adw]

The reason for the change of part no. Was extra insulation around the wires were they enter the crankcase, there was an issue with them grounding out in this area.

[Guest Gimlet]

Don't want to hijack the thread, but may I ask, what would be causing the milky clogging of the carb diaphragms in mine, given that my other saw runs perfectly on the same fuel? If it's not the fuel it must be the saw and I don't want to pay for a strip down (and by the sound of it, a coil) if it's just going to happen again.

[Mark_Skyland]

7 hours ago, butters said:

Will be the coil. I’ve got 2 550’s that are in all the time for new coils. 
 

according to the dealer husqvarna have changed the part number for the coil so hopefully they have fixed the issues. One saw I’ve had has gone through 3 coils in 9 months. 
 

amazing saws when working but getting tired of coil issues now. 

That's a bit strange. Is it the coil breaking down or as adw says is it the wiring rubbing on the casing?

[adw]

If it’s in the carb then it must be coming from whatever is in the fuel tank, drain the tank fit a new filter( there is a blue top very fine fuel filter available ) a try again.

[Guest Gimlet]

16 minutes ago, Mark_Skyland said:

That's a bit strange. Is it the coil breaking down or as adw says is it the wiring rubbing on the casing?

I've had coils break down on older motorbikes. It was usually on air cooled engines which run hotter than liquid-cooled, and the coils were always tucked under the tank right on top of the engine with little air flow to cool them. A tiny heat-stress break in the winding could occur if the engine got too hot and it would widen with expansion as the unit heated up until the circuit was lost producing a miss-fire. It was a common problem (it happened with condensers too on crankshaft-mounted alternators) and might explain why a similar fault in a chainsaw takes fifteen minutes or so of use to show up, and disappears again when the saw is cold.

Edited January 15, 2023 by Gimlet

[Guest Gimlet]

Got this fixed as well now. It was the spark arrester in the exhaust. Got clogged up because I'm not revving it hard enough with hedging work. 

 

They've taken it out and reflashed the engine management system. Hopefully that will sort it, but I'll be making sure its a regular proper workout on high revs. 

[Stubby]

12 hours ago, Gimlet said:

Got this fixed as well now. It was the spark arrester in the exhaust. Got clogged up because I'm not revving it hard enough with hedging work. 

 

They've taken it out and reflashed the engine management system. Hopefully that will sort it, but I'll be making sure its a regular proper workout on high revs. 

That's the first thing I remove when I buy a new saw . 🙂