Stihl 08s Project Rebuild

[Vintage Engine Repairs]

Hi, another project and hopefully challenges to overcome.

This time a stihl 08s again for the owner of my local Stihl shop.




It’s having a full overhaul as well as some fabrication of a new handle brace pocket (notorious for mag rot and this is no different). More on that later.

I did the tear down today and there are 3 notable mentions so far.

First, removing the clutch side key.

Someone was in this saw before me and had a good go at removing it unsuccessfully, it was well and truly stuck and beaten up.

I initially tried getting a pick inbeteeen the flywheel and key to no avail. Then I tried carefully with a screwdriver with no luck.

Then I tried some penetrant and the above methods with no success.

Then I tried heat and penetrant and the above being very aware not to go above 150c checking with an IRT as it would start to affect the metal temper. Nothing..

Then I decided to drill a 4mm hole in the key and tap the threads and pull it out. Knowing the key is soft I did question if the threads would just rip out. Therefore if that failed my backup was to then tap to a 4mm thread repair. If that failed I’d move up to 5 and so on.

Anyway, drilled, tapped and used two hammers and after a few knocks of the hammers the key eventually came out.




Damaged key, well and truly stuck in
No damage to the crank (I stopped drilling as soon as I felt slight resistance / the inability to keep going) and it hardly left even a mark.

See next thread for the next two notable mentions so far..

 

[Vintage Engine Repairs]

The next notable mention is the piston... once again, someone had used a metal piston stop and damaged the crown of another piston...
The damage, just like on the 045 build I did, went through and cracked the underside. It will be replaced...
I have seen so many good pistons damaged from misuse of rope or metal piston stops...

The third notable mention was when the previous person working on the saw wasn’t careful with how he had put the wires back under the flywheel. I always double check wires won’t get caught and this is why.. it was on the outside of the stator plate and got abraded away. There wasn’t any spark on this old girl and here is why.


Cracked HT lead would cause grounding too:


Ah yes, and a 3rd reason this wouldn’t make spark.. who needs an air gap anyway?! It’s almost like they tried to purposely avoid getting spark! (Maybe he needed an excuse with the mrs for a new saw?)

 

[GeorgiaVol]

The next notable mention is the piston... once again, someone had used a metal piston stop and damaged the crown of another piston...
The damage, just like on the 045 build I did, went through and cracked the underside. It will be replaced...
I have seen so many good pistons damaged from misuse of rope or metal piston stops...View attachment 906742

The third notable mention was when the previous person working on the saw wasn’t careful with how he had put the wires back under the flywheel. I always double check wires won’t get caught and this is why.. it was on the outside of the stator plate and got abraded away. There wasn’t any spark on this old girl and here is why.View attachment 906743View attachment 906744


Cracked HT lead would cause grounding too:
View attachment 906745

Ah yes, and a 3rd reason this wouldn’t make spark.. who needs an air gap anyway?! It’s almost like they tried to purposely avoid getting spark! (Maybe he needed an excuse with the mrs for a new saw?)
View attachment 906746

Still working on one of these I never got around to finishing. Looking forward to your build!

 

[ozziechainsaw]

Love the Stihl 08 saws. I will follow this closely.

Justin

 

[KASH]

Best saw ever made dead nuts reliable only weak spot is is handle bar mount on the oil tank.The muffler on that saw is from a cut off saw or brush cutter. I feel kinda happy for that saw because the way you operate there wont be a square inch of it that wont be examined by your microscopic eyes.Good luck I will be following .
Kash

 

[Vintage Engine Repairs]

Best saw ever made dead nuts reliable only weak spot is is handle bar mount on the oil tank.The muffler on that saw is from a cut off saw or brush cutter. I feel kinda happy for that saw because the way you operate there wont be a square inch of it that wont be examined by your microscopic eyes.Good luck I will be following .
Kash

Thanks KASH mate, should be fun!

I’m interested in the muffler comment you made. How do you know it’s not from the standard chainsaw version of the 08s? I may have to swap it if that’s the case. They show two options in the IPL mines the bottom one, but don’t specify what they were used on.

 

[scallywag]

They show two options in the IPL mines the bottom one, but don’t specify what they were used on.

The 08/08S was used as a power head for lots a things!.....Such as the Stihl P840 water pump, these pumps used a very similar muffler to the large rectangular one in your IPL, see below.

[Edit] Post #10 in this link has some good pics....
https://www.arboristsite.com/community/threads/stihl-p840-water-pump.288993/

 

[Vintage Engine Repairs]

The 08/08S was used as a power head for lots a things!.....Such as the Stihl P840 water pump, these pumps used a very similar muffler to the large rectangular one in your IPL, see below.
View attachment 906930
[Edit] Post #10 in this link has some good pics....
https://www.arboristsite.com/community/threads/stihl-p840-water-pump.288993/

Good to hear from you scallywag. Correct yes they did use the 08s for lots of applications, I just wasn’t sure how the mufflers were specific to applications too. Thanks for that, I’ll check it out!

 

[Vintage Engine Repairs]

Time to start the fabrication / repair of this pocket.

8 keys cut and flattened metal wire to sit in each keyway.

 

[ozziechainsaw]

Hi Tom,

Can I ask what type of JB Weld you are using ?

I have a Stihl 08S apart now needing a rebuild as well, just too many other chainsaws getting in the way. But I think looking at this I need to get back onto it ASAP.

Cheers

Justin

 

[Vintage Engine Repairs]

Hi Tom,

Can I ask what type of JB Weld you are using ?

I have a Stihl 08S apart now needing a rebuild as well, just too many other chainsaws getting in the way. But I think looking at this I need to get back onto it ASAP.

Cheers

Justin

Hi Justin, I use the original “cold weld” slow cure, repco sells it.

 

[Bob Hedgecutter]

Best saw ever made dead nuts reliable only weak spot is is handle bar mount on the oil tank.The muffler on that saw is from a cut off saw or brush cutter. I feel kinda happy for that saw because the way you operate there wont be a square inch of it that wont be examined by your microscopic eyes.Good luck I will be following .
Kash

Nope- it is square micron now- square inch is considered aftermarket on Stihl saws.

 

[Vintage Engine Repairs]

I have JB welded the ends - tomorrow I’ll remove the amine blush, dremel to shape the ends and then do more Jb weld. I’ll use a flat reference surface that’ll put grease paper on. Apply Jb weld to that and sit this case on it. Then I’ll wipe the excess flat on the inside. Let that set and then build up some more..

 

[Vintage Engine Repairs]

I have removed the amine blush and shaped / profiled the metal. Removed a very slight amount of the parent material so the Jb weld will build back to the original size.
Ready for coat 2



Next layer of Jb, this time the flat medium (float glass) is pressing Jb in between the flattened wire strips. grease paper will peel off and give me a flat surface to build up on both inside the pocket a little (to smooth out the undulations of the alternating wire and space, but mostly the outside.



One smooth surface

 

[ozziechainsaw]

Impressive work mate.

 

[Vintage Engine Repairs]

Impressive work mate.

Thank you!

 

[Vintage Engine Repairs]

Ok, that’s a great foundation to build on. I’ll rough it up well and apply multiple coats in the same fashion.

 

[Canyon Angler]

Given the choice, you're generally better off spending a couple of hours -- rather than several months -- building up your composite. It doesn't need to be as complicated as you're making it.

If you apply one coat of epoxy while the underlying layer is still green (i.e., when you can still dig your fingernail into it), not only do you not have to deblush, but you also get the benefit of the new layer of epoxy bonding chemically -- rather than just mechanically -- with the previous layer. Win-win.

On the other hand, if you drag out the process, deblushing ALONE can end up eating up half of your time when boat building or bottom coating. HUGE waste of time, labor and materials. You also run the risk of not deblushing well enough, and having your composite fail as a result. In other words, there are basically ZERO benefits to dragging it out but many reasons to GTF on with it.

 

[StihlSolo]

Stihl Australia may have had the muffler you have as stock/oem for your country. In USA that muffler was used on TS350 and other apps. It is quieter than the USA 08s muffler. I've had that muffler on my late 08s frankensaw and on my TS350. There are two types of "big" mufflers: one with the exhaust pipe/stinger like yours and the other with exhaust gills as shown at post #7 attachments & link.

I've attached IPL pages for the 08s muffler versus TS350 stingered muffler differences.

 

[StihlSolo]

...and I've shown a photo of my 08s quickstop frankensaw before. It's a bit more used than in this photo. Built it with TS350 muffler, 60cc piston & cylinder and intake bell with triple filters.