Stihl 026 PRO

[openspaceman]

33 minutes ago, bmp01 said:

Nope. 
Turning the screw clockwise is ‘closing the tap’ - saw will run leaner.

 

In your other comments you said turning screw counter-clockwise helped the saw run better (for a bit) - in this case you were adding extra fuel …. It’s likely the extra fuel is helping compensate for an air leak or an issue with fuel delivery. Be cautious, find the cause for the original failure before it repeats. I know this is repeat advice, Stubby, but…..well… it’s right innit.

Great to see you back posting. I have an old but little used, you can still see the machining marks on the piston through the exhaust port, 026 on my bench, that I cannot get to fire, despite a spark when the plug is out and having tried another good plug.

 

Can one tell by looking at the coil trigger pick up relation to the flywheel magnet when piston is tdc if the timing is okay/

[bmp01]

44 minutes ago, openspaceman said:

 

Can one tell by looking at the coil trigger pick up relation to the flywheel magnet when piston is tdc if the timing is okay/

Maybe but I’ve not owned one so can’t add detail, sorry. Could be a few different flywheels/ coil combinations to mess up timing….

I guess you’ve tried Spuds bend the plug terminal to get the spark to jump bigger gap…establish if coil is really healthy (not just pretending   ) ……. heading off piste here aren’t we…..

 

 

 

[openspaceman]

1 hour ago, bmp01 said:

 

I guess you’ve tried Spuds bend the plug terminal to get the spark to jump bigger gap…establish if coil is really healthy (not just pretending   ) …….

It sparks when the gap is opened up to ~1/8". He had been having trouble with hot starting which I guessed was weak mixture. I had fitted an aftermarket coil to it about a year ago. The current failure was when the on off switch jammed in the part throttle setting, so it had to be choked to stop it, it has not fired since. I wanted to avoid checking the flywheel key until I was confident the timing was out.

 

Having another 026 would be handy to compare.

1 hour ago, bmp01 said:

 

 

 

 

[bmp01]

27 minutes ago, openspaceman said:

It sparks when the gap is opened up to ~1/8". He had been having trouble with hot starting which I guessed was weak mixture. I had fitted an aftermarket coil to it about a year ago. The current failure was when the on off switch jammed in the part throttle setting, so it had to be choked to stop it, it has not fired since. I wanted to avoid checking the flywheel key until I was confident the timing was out.

 

Having another 026 would be handy to compare.

 

A bit of history with that saw then. Aftermarket coil rings alarm bells for me. What about a strobe light, could you use that at pull cord speed to see where it’s sparking? Does the flywheel have features to pull it off nicely - I expect Spuds workshop manual (posted earlier in the thread) would tell you. 

[openspaceman]

6 minutes ago, bmp01 said:

A bit of history with that saw then. Aftermarket coil rings alarm bells for me. What about a strobe light, could you use that at pull cord speed to see where it’s sparking? Does the flywheel have features to pull it off nicely - I expect Spuds workshop manual (posted earlier in the thread) would tell you. 

I have an old timing light strobe I can try in the dark. My guess is I would have to spin the motor with a drill. Yes the after market coil is the most likely suspect but at £110  for the Stihl part probably not an economic repair. I'll have a look at spuds post when back at my desktop. 

[spudulike]

Those aftermarket coils can be pretty crap at best. I think form memory, a lot of Stihls use the same coil and just fit other HT leads to suit different machines so perhaps a MS200T one would fit as the HT cable can be removed and swapped. 

On the flywheel key, I would expect the magnets would align with the coil at around 10 degrees in advance to TDC. It is unusual for this to not be the case but have seen some strange exceptions up to 180 degrees out! The difficulty will be if the key has just slipped a few degrees out as it will be more difficult to find.

Again from memory, I think the 026 flywheel is removed by the screw in puller which makes pulling off the flywheel a breeze.

The 026 kill wires can rub around the top AV mount giving some annoying HT issues.

I usually try a second user OEM coil from the bay rather than the Chinese poop. More reliable.

[openspaceman]

I will take the flywheel off but agree it is probably the coil. The frustrating thing is at work we had a box of broken 026 where i could find bits as the were replaced by ms261.

[openspaceman]

On 30/01/2025 at 21:29, openspaceman said:

I will take the flywheel off but agree it is probably the coil. The frustrating thing is at work we had a box of broken 026 where i could find bits as the were replaced by ms261.

An update; it looks like I did the owner a disservice by fitting an aftermarket coil.

 

I was preparing to check the timing with a strobe as per @bmp01's suggestion and waited for dusk. I did some test pulls and found it sparked well three times then nothing, next pull nothing. Left for an hour and same again.

 

The owner, a chap that was at primary school with me, can no longer handle a chainsaw . I have put it back on the shelf as , although it is still a nice saw, the £130 for a genuine part isn't justified as I already have far too many saws and I suspect a carburation problem too.

 

I may well decide to get it going in the future, either with a new coil or a secondhand one.

[spudulike]

Stihl Ms240 Ms260 Petrol Chainsaw Tested Ignition Coil & Flywheel 1121 024 026

WWW.EBAY.CO.UK

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<p>Stihl ms240 Petrol Chainsaw </p><p>Tested ignition coil and flywheel </p><p>One fin missing on flywheel </p><p>Genuine used part</p><p>Please see pictures </p><p>All questions...

 

[openspaceman]

Thanks spud, I'll give it a whirl and let you know