Stihl 041 weak spark - what to check?

[Joepro]

Hi all,

I have recently purchased a "spares or repairs" Stihl 041av Electronic chainsaw from ebay. I like Stihl equipment and just want to get it running again for occasional DIY use along with my other saws.

So far I have:

Cleaned and rebuilt the carb
Tested compression and got 145psi
Replaced the pull cord and gobbins of that setup. (Plastic ring and friction plate)
Cleaned fuel tank, new fuel line.

Tested spark and it was showing a light orange spark in my inline ignition tester.

I tried to start it and it only coughed once. Basically dead otherwise. Adding raw fuel into intake made no difference either so I believe it may be a weak spark issue.

This is what the ignition system on it looks like:





Google isn't showing me much on this. I am hoping members here might have some suggestions on what I can check here first please?

 

[Joepro]

I was also looking at the universal ignition conversion kits (the Nova box is that what it's called?) But those are noted as not suitable for multiple magnet flywheels so seem like a no go.

Or this kit looks interesting too

https://shop.saegenspezi.de/electro...i-ignitions-fits-Stihl-040-041-AV-040AV-041AV

 

[hotshot]

That looks like an early 3 piece Bosch system that used an ignition module mounted under the top cover/handle. Have you ever taken the air filter cover & AF base off?

What parts numbers are stamped on the flywheel rim?, as it should not be a SEM nor made in Sweden. Mismatched parts are common on those 50+ yo saws.

How many wires are exiting the ignition area behind the flywheel?, of course you’ll have at minimum one wire to the kill switch.

Saegenspezi has a note in that aftermarket CD ignition description that their CDI module is “Not suitable, if a capacitor was installed before”…and that can in your first pic is a capacitor.

 

[ZeroJunk]

I would make sure it has good electrical continuity to ground and that those ring terminals have continuity.
Looks a little oxidized.

 

[Joepro]

That looks like an early 3 piece Bosch system that used an ignition module mounted under the top cover/handle. Have you ever taken the air filter cover & AF base off?

What parts numbers are stamped on the flywheel rim?, as it should not be a SEM nor made in Sweden. Mismatched parts are common on those 50+ yo saws.

How many wires are exiting the ignition area behind the flywheel?, of course you’ll have at minimum one wire to the kill switch.

Saegenspezi has a note in that aftermarket CD ignition description that their CDI module is “Not suitable, if a capacitor was installed before”…and that can in your first pic is a capacitor.

Thanks for the reply, yes here is under the air filter area



There are no other electronic parts in there.

Yes you are correct about that aftermarket solution. They also have a version to replace points setup and which therefore works with a points flywheel. I have found a points flywheel on ebay too so that could work.

I have not had the 3 screw starter cover off the flywheel yet to check the part number / type. I will check that tomorrow also

 

[Joepro]

I would make sure it has good electrical continuity to ground and that those ring terminals have continuity.
Looks a little oxidized.

I only got the flywheel tool and got it off today so I will try and carefully take apart and clean all connections and try again with this setup before condemning it

 

[hotshot]

Thanks for the reply, yes here is under the air filter area

View attachment 1200159

There are no other electronic parts in there.

Yes you are correct about that aftermarket solution. They also have a version to replace points setup and which therefore works with a points flywheel. I have found a points flywheel on ebay too so that could work.

I have not had the 3 screw starter cover off the flywheel yet to check the part number / type. I will check that tomorrow also

I believe that silver box in the lower right of your pic is a module. European only, I’ve never seen one in the US. You should try to get an IPL & service manual for your 041AV Euro version from the ‘beg for manuals’ link below:

https://www.arboristsite.com/threads/the-beg-for-manuals-thread.68615/unread

Here’s an old link at chainsawcollectors forum about a similar issue like you have:

********************************/phpbb3/viewtopic.php?style=23&t=34335&view=previous

I guess AS blocks that website, just go there & search for AV-69.

 

[Joepro]

This is the original flywheel part number that came off my saw. To be honest it feels like no one has ever been in there before! Everything is rusty, tight and undisturbed



I will try cleaning up all of the connections first later and test resistance on the spark plug lead too.

 

[Joepro]

OK so there is a wire on the coil which feels very weak and about to break off. Corrosion has wicked into the cable it seems right at the coil pack.

There are 2 wires headed to the module. And the kill switch goes to that module too.





Considering the corrosion etc I have to put a value on my time and sanity too!

So I went ahead and ordered the new kit along with a good used bosch 041 points type flywheel from ebay to match:

electronic ignition (replaces contact breaker ignition) fits Stihl 040 041 AV 040AV 041AV

 

[Joepro]

I guess it will take a week or two for the new parts to get here. Fingers crossed it will resolve the issue and besides that at least I can rule out ignition system and know it has a new fresh system in there for the next 50 years!

Either way I will report back when I get the new parts and try it out. Many thanks for the help so far.

 

[stihltech]

Well you need an old fart to remember these things. I started in 81 and they were old then. My guess is the60s and 70s.
About your only course of action with the original is cleaning mounting points and check wires.
Yes that is a module under the air filter.
In the past I replaced the electronics with a complete points setup, as I had lots of those at the time. And points were very durable on an 041.
Be careful of crankshaft taper. It seems the very early ones had a thinner taper than the newer ones.

 

[Joepro]

The ebay seller of the flywheel also had a very clean set of original 041 points going cheap (£10) so I ordered them too just to have some parts to get this saw going. For example if there is any trouble with the new electronic setup then I could revert to the points with points flywheel.



For the £, was worth ordering for the spares drawers!

 

[hotshot]

Good decisions, you’ll be running & cutting in no time!