Stihl 024 to 026 Needs Some TLC

[Gunn]

The 024 super conversions were never in question though.

 

[T.Roller]

The 024 AV that I rebuilt (the one that works flawlessly) was run over by a pickup truck. The case survived but almost nothing else did. New tank housing, new plastic, new top end, new bar studs, new shock mounts, new chain brake, new outer handle, new trigger, etc. The owner wanted too see if I could restore it because his late brother bought it (and ran over it). Total cost of all parts was about the same as a new MS 240.

Mine needs a new flywheel side case half and clutch cover. I got lucky

 

[drf256]

Please check your squish.

Are you gasket delete?

 

[jacob j.]

Well, it does also seem reasonable to check the squish to be sure before I tear it down. I rebuilt an 024 AV Wood Boss with the same new top end kit and the owner says it runs flawlessly. Also, if compression were really that bad, it seems like it would not start and idle correctly. I'll check compression also. This one is still somewhat of a a mystery to me.

All of the Wood Boss saws I've taken apart had the crank as the Super, but I remember seeing a service bulletin somewhere that stated there was a change in crankshafts in the middle of the production run.

 

[stihl saws]

Has the debate about 024 vs 026 crankcases ever concluded?

Some people claim a crank swap is all that's needed with the 024 to use the 026 top end.

Others claim there's differences between the 024 vs 026 crankcases and the rod angle is incorrect is you swap in an 026 crank?

The cases are the same. The only differences are the cranks and cylinders.

 

[Wagnerwerks]

I think I have a whole 024 bottom end here. It's beEn open F oR. A while, but the case halves werE very nice.

 

[drf256]

Edwin,

I'm very interested in your findings.

If you used an standard 30mm vs 32mm crank, your squish would be .040 bigger. It wouldn't be .080 bigger because it's 1mm in each direction.

026 jugs have roughly .010 squish without a gasket on an 026 case and crank. We've all seen AM jugs run fine, but not great, at .050 or more squish.

My bet here is that you've got .050-.070 squish, depending on whether or not you used a base gasket.

The lack of compression will hurt torque, but the timing will really be off and affect performance even more so.

All of the 026/260 jugs I've ever seen have a .250-.262 base thickness with the 260's being on the thicker side. Gasket free, you should be able to pull .030 off the base to get to a .020 squish.

Where your timing is intrigues me the most. If you really do have the 30mm crank, everything should be occurring later. So you should have a lower exhaust for degree of crank rotation and a lower intake. The lower intake is what is likely hurting performance the most.

Please take a squish measurement and let us know.

 

[paragonbuilder]

My bad... I forgot about the 2mm total stoke being 1mm less height.
Whoopsie! Thanks for the correction Al. [emoji106]


Sent from my iPhone using Tapatalk

 

[odin]

All of the Wood Boss saws I've taken apart had the crank as the Super, but I remember seeing a service bulletin somewhere that stated there was a change in crankshafts in the middle of the production run.

The IPL I've got in front of me (there were two or three posted by DefDave in the Technical Section) lists four versions of the 024. Two standard versions: 024 AVEQ and 024 AVEQWB. Then the two Super versions: 024 AVSEQ and 024 AVSEQW.

It seems obvious that at least one standard version was a Wood Boss (AVEQWB). And I would assume the latter of the two Super versions is a Wood Boss as well (AVSEQW). I would also venture a guess that Stihl didn't care to use more than six letters in designating any model saw, which is why we see the lone "W" designating the Super version of the Wood Boss.

Downloading all the IPL's you can get your hands on and cross-checking your cylinder numbers seems the best course of action when digging into one of these saws IMHO.

 

[Wagnerwerks]

I had an 024 wb that was standard stroke and one with a 026 stroke. I've also had an avs and an 026 pro.

I parted out all but the 024avs which Kieth got. I checked everything before parting them so I'm sure they were what they were.

 

[Wood Doctor]

Please check your squish.

Are you gasket delete?

OK, here's the squish: 0.038"
Compression cold: 126 psi
Compression warm: 129 psi
Cylinder gasket is in place. Rings, unfortunately, look marginal and there is some obvious wear on the exhaust side. Not sure how that happened, but I did loan the saw out once or twice. I think a second attempt on another top-end rebuild is in order. If so, I'll go back to the standard 024 cylinder and piston.

Does that seem like a plan?

 

[paragonbuilder]

OK, here's the squish: 0.038"
Compression cold: 126 psi
Compression warm: 129 psi
Cylinder gasket is in place. Rings, unfortunately, look marginal and there is some obvious wear on the exhaust side. Not sure how that happened, but I did loan the saw out once or twice. I think a second attempt on another top-end rebuild is in order. If so, I'll go back to the standard 024 cylinder and piston.

Does that seem like a plan?

Looks like you have the 026 crank as you thought! Can you throw a timing wheel on it before you disassemble it?


Sent from my iPhone using Tapatalk

 

[Wood Doctor]

Looks like you have the 026 crank as you thought! Can you throw a timing wheel on it before you disassemble it?
Sent from my iPhone using Tapatalk

No, I think it's still the original crank. That takes real work to replace the crank. I have never split the case. New top end is all that it needs now, assuming I want that compression back up and the original power. I searched around and found an 024 cylinder kit already in my inventory, ready to be installed.

I have a pair of 026 PROs on board and both run well. So, a new o24 top end is really all I need to bring this saw back up to snuff. No reason to soup it up again. Looks like the guys who borrowed it tried to lean it out and see what it could do, but I don't want to start a war with them.

 

[paragonbuilder]

I was referring to your comment on the wood boss having the 32 mm stroke. Which means it essentially is an 026 with that 026 top end on it.
I think if you want to go back to an 024 top end it will have to be an 024 super or it will be a head banger.


Sent from my iPhone using Tapatalk

 

[Wood Doctor]

Very good, I will check that very carefully. It ever ceases to amaze me how many variables are involved when it comes time to overhaul an engine. Whoever said this was a piece of cake? Believe me, I never did.

 

[T.Roller]

I'd pull the base gasket and check squish. When I deleted my base gasket I had to add a piece of .008 flashing I made into a spacer cause the squish was too tight

 

[huskihl]

There's a huge power gain going from .040 to .020 squish IME

 

[T.Roller]

There's a huge power gain going from .040 to .020 squish IME

Thats a fact!

 

[paragonbuilder]

I'd pull the base gasket and check squish. When I deleted my base gasket I had to add a piece of .008 flashing I made into a spacer cause the squish was too tight

I like to delete the gasket and sand the squish if I need to instead of making a gasket. On an 024/026 I'd be quite happy at .015 squish.


Sent from my iPhone using Tapatalk

 

[jacob j.]

OK, here's the squish: 0.038"
Compression cold: 126 psi
Compression warm: 129 psi
Cylinder gasket is in place. Rings, unfortunately, look marginal and there is some obvious wear on the exhaust side. Not sure how that happened, but I did loan the saw out once or twice. I think a second attempt on another top-end rebuild is in order. If so, I'll go back to the standard 024 cylinder and piston.

Does that seem like a plan?

You might get by with just new rings or a new piston and rings. Is this an aftermarket top end?

Always go back to the basics- worn ring(s): low power, more smoke.