No Spark generation on Husq 550 XP chainsaw Likely Cause

[cjdg]

I have two of these machines one mark 1 one mark 2 (I think!), lets call them A and B. My "regular" one A has been good as gold until a month ago.  It was always a bit of a b^&&£r to start but then it went dead.  Checked the plug sparking by taking out plug of A and turning over. No spark.  Put the plug out of B which worked and checked that in A.  No spark .  Took the plug out of B which worked in B  and swapped over the plug  to A  No Spark.  Checked therefore both plugs in B and there is nothing wrong with the plugs.  So it must be the generation of the spark   Now I am an old old git close to 80 and I was brought up on motorbikes with. contact breakers and magnetos etc etc so I do not have a clue as to what generates the spark but suspect it is some form of electronic chip/package that you screw in and out.  Where do I start looking for a solution?

[openspaceman]

18 minutes ago, cjdg said:

I have two of these machines one mark 1 one mark 2 (I think!), lets call them A and B. My "regular" one A has been good as gold until a month ago.  It was always a bit of a b^&&£r to start but then it went dead.  Checked the plug sparking by taking out plug of A and turning over. No spark.  Put the plug out of B which worked and checked that in A.  No spark .  Took the plug out of B which worked in B  and swapped over the plug  to A  No Spark.  Checked therefore both plugs in B and there is nothing wrong with the plugs.  So it must be the generation of the spark   Now I am an old old git close to 80 and I was brought up on motorbikes with. contact breakers and magnetos etc etc so I do not have a clue as to what generates the spark but suspect it is some form of electronic chip/package that you screw in and out.  Where do I start looking for a solution?

It has capacitor discharge ignition, the magnets in the flywheel charge up a capacitor and then as they pass the trigger pick up  transistors dump the charge into the coil which generates the spark. The motor has to spin at more than 400rpm before this happens.

 

All the electronics are embedded in the coil encapsulation and modern coils also advance the ignition as revs increase.

[Stubby]

Check the flywheel gap to the electronic billydoo . Also flywheel magnets have been known to loose their power . Check to see if anything is shorting to earth . ( would be like pressing the stop switch )

[adw]

If it has no spark at the plug ( they do work off speed of rotation, so make sure you give it a good crank ) then it will require a replacement unit, the mark 1 is a little more difficult to fit due to the earth wire running behind the carb.

mark 1 has a deco valve, the mark 11 has no deco valve.

[woody paul]

Check plug cap is all as it should be, had a saw that played up like that and turned out, bit that connected to lead had lost it's spike. 

[openspaceman]

1 hour ago, adw said:

If it has no spark at the plug ( they do work off speed of rotation, so make sure you give it a good crank ) then it will require a replacement unit, the mark 1 is a little more difficult to fit due to the earth wire running behind the carb.

mark 1 has a deco valve, the mark 11 has no deco valve.

Yes and they are different coils for mk1 and mk2. Watch the price mk2  used to be a lot more, about 80 quid, than the other and some dealers may still have stock at a higher price.

 

See:

 

Edited November 23 by openspaceman

[Mark_Skyland]

Just follow the HT lead back from the sark  plug. It will end up at the coil which is located behind the starter cover to the left. The coil has some number on it, this is an example 581 72 36 02. Its best if you match the coil numbers otherwise you may have to take the machine into a husky dealer to get them to update the autotune.

Replacing the coil on the mark 1 is a bit of a job IIrc, although I may be mixing that up with the 560. To make it easier you can cut the wires from the coil and join them to the original wires on the machine.

 

 

 

[adw]

Unfortunately the part no. on the ignition unit will be the unit on its own which does not exist, it comes as an assembly with the wires and cover so gets a completely different number, both mark 1 and mark 2 will require removal of the carb to ease fitting, and also the flywheel on the mark 1, there will be no need to update the firmware if just changing the ignition unit, the air gap should be 0.3mm, if you need a shop manual pm me.

[Donnie]

Here is my 4 day old 550 mk2 and this is how I have to unstick the pull start (never in my 2 years softwood cutting have I experienced this so quick). 
 

Kill switch is also tempermental straight out the box. 
 

Saw is flying though

[Mark_Skyland]

On 24/11/2024 at 16:41, adw said:

Unfortunately the part no. on the ignition unit will be the unit on its own which does not exist, it comes as an assembly with the wires and cover so gets a completely different number, both mark 1 and mark 2 will require removal of the carb to ease fitting, and also the flywheel on the mark 1, there will be no need to update the firmware if just changing the ignition unit, the air gap should be 0.3mm, if you need a shop manual pm me.

I thought that if you say use an updated coil, or the numbers on the unit where different then the firmware needed updating as it always asks which ignition unit is fitted. Good to know that it doesn't matter.