Husqvarna 550XP intermittent power mystery.

[Hoggin]

I have an odd problem with my 550XP. It will run fine for 15-20 minutes then it starts to play up. With the throttle held wide open the power is intermittent. If I shut it down and go back to it the next day, the same thing happens.

 

I’ve taken it in to the local Husqvarna dealer and they thought they had fixed it. Unfortunately not, although it does start more easily.

 

I managed to get a couple of videos of what is happening. The first is when the problem first appeared, the second is just after I got it back from the dealer. Note that it happening with the throttle held wide open.

 

Has anybody got any ideas as to what the cause and fix is?
 

YouTube video 1

I thought it might be a problem with E10 fuel so tried some Husqvarna premixed fuel. Same problem.

 

YouTube video 2

Thanks.

 

[spudulike]

It would be interesting to see the CST download the dealer got from the machine. Not seen one doing this sort of thing before and always difficult to diagnose without any background info as to how this running issue started i.e......after another issue, after a service, just started happening etc.

The carb H&L settings from this download would be of interest from this download.

I would normally go through a service and see if it still happens although it does seem a strange one.

Things to check...the air filter is 100% clean...some wash in water and the scum blocks the open areas...get some solvent on it and clean the open areas with a compressor airline.

Change the spark plug...do check the colour as it will give decent info...make sure it is a resistive plug of the correct type.

Strip the carb checking the gauze strainer is clear and the metering diaphragm is good and not distorted...seen this on 540XPTs. 

Reassemble and try again. What did the dealer do? It may be a dodgy coil but I would usually use the CST info and normal diagnostics to find the issue.

Does the saw have good compression and start cleanly from cold and hot?

 

[Hoggin]

Thanks for the response. I didn’t get any feedback from the dealer as the bloke that did the job was out when I picked the saw up. Unhelpfully, the job card just said “repair”. I was unaware of the CST info, so will get back to them and see if they kept a copy and what they actually did to the saw. I might ask them to download the CST again if the didn’t.

 

The problem just started happening. Admittedly I had been working it hard all day on a fallen ash. I serviced the saw with a new plug and air filter thinking that might be the problem. I did notice that some very fine dust had been getting past the filter. I’ll double check that the new and old plug were the correct type, although I’m pretty certain they are.

 

I did wonder about the coil breaking down when the saw gets hot.

 

I haven’t tested the compression, but it seems fine. Starting isn’t a problem hot or cold.

 

Cheers

 

[peatff]

What was the air temperature at the time the saw was acting up. A friend has a 550xp which was acting weird during the hot spell but has gone back to normal now.

[Hoggin]

Not that warm. The second video was last Monday… in Wales.

[adw]

A couple of things here, the throttle shaft on the l/h side of the carb has two very small magnets pressed into a white bracket, as the throttle is opened these pass the auto tune unit telling it its revving up, if one of the magnets have come out you will get something like this, if they are there then this is an ignition coil issue.

[spudulike]

Part of the CST test is a "Throttle Open" and "Throttle Closed", if ADW is correct, the test should register an issue on this part of the test. He does know a little about Husqvarnas

[Hoggin]

Cheers. All good info.

 

I haven’t had a chance to look at it today. My wife’s car is due it’s MoT on Friday. Fine all year but yesterday the exhaust started blowing. Today the handbrake seized on. I’ve been a bit distracted.

 

I’ll get the saw in the bench tomorrow and check over the points raised.

[Bolt]

23 hours ago, Hoggin said:

I have an odd problem with my 550XP. 

 

 

I expect we will see more and more of this in the future.

 

Although you assume you have a petrol saw, it is clearly identifying as a diesel.  
 

Possibly a Lister AC1.

 

The CST will hopefully reveal your saws pronouns.

 

[Hoggin]

It would be nice if it identified as a 560. I’ve got some big stuff to cut up.