Stihl West German O24 AVS / Upgrade to 44.7 Bore

[drf256]

Pulled the muffler to have a look at the piston and rings, all good, no marks at all. What I could see on the inside of the cylinder looked perfect:
View attachment 358299

View attachment 358300

Found one of the muffler to cylinder bolts loose inside the muffler. Used Hot-Lock on all 4 muffler bolts to prevent them from coming out prematurely in the future

Who ground on the exhaust port?

 

[Paul Fithian]

Not me, I didn’t touch it. Did you have a go at some years ago Doc?

 

[drf256]

Not me. Thought stock. Could be illusion.

 

[Paul Fithian]

It appeared non-stock to me as well upon closer look. Maybe I should put a timing wheel on this? I need one to do any port work, right?

 

[lehman live edge slab]

Not me. Thought stock. Could be illusion.

Does look like it was ground on I the picture. Looks like it was widened and the exhaust roof looks altered some because it almost looks like it has a rise in it

 

[drf256]

I did not grind on that. Had some carbon in the exhaust outer port, so I must have missed that.

The inner port at the plating was certainly stock. That was looked at before I sent it to you. That roof looks inconsistently ground, but it must only be outside the plating. No one that knows what they are doing would have done that to the jug.

The saw has too much exhaust timing stock for a 50cc saw. We try out best to get that exhaust roof lower by cutting the band and base. No one that knows that saw model raises the roof. I widen the port and blend the arc of the sides into the stock roof.

If you want to play with porting you will ruin a few jugs in the process. Start with an AM cylinder first. I have a few paperweights/doorstops here you can have.

 

[drf256]

This is what a widened and finished 026 ex port should look like IMHO.

The ugly opening in the center of the roof is STOCK. You can see how that’s been left alone and everything blended into it if you look carefully.

 

[Paul Fithian]

For sure you guys know way more about this than I do, and I greatly appreciate the ability to learn from the gurus here.

This 024 AVS is the only chain saw I have ever owned, and has served me well for over 35 years. It's now way more powerful than it was new and runs perfect, thanks to your contributions, especially Doc's. Before the aftermarket P/C swap a few years ago and this recent upgrade, all I've ever done to it is replace a starting pawl and run it out of gas before it went back into the case, sometimes for a year or more before using again.

I'm happy to put a timing wheel on this if we think it will help understand what's going on. But a big part of me suggests leaving it alone and using it for the next decade or so, as I'm not sure it could be improved further for my intended use.

Santa is bringing me another dead West German 024 AV powerhead that I'll make into a 16" bar saw with some of the bits I have leftover from this upgrade. Anyone have a top and air filter cover in decent shape for one of these? Maybe I'll play with porting and timing on this one:

 

[Paul Fithian]

This saw did a lot of work today

 

[lehman live edge slab]

This is what a widened and finished 026 ex port should look like IMHO.

The ugly opening in the center of the roof is STOCK. You can see how that’s been left alone and everything blended into it if you look carefully.

View attachment 358479 View attachment 358480 View attachment 358481 View attachment 358482

This is a pretty ugly factory port roof isn’t it, do they all look like that on the 260’s? Don’t recall seeing any of the 024/026 cylinders I have had look like that.

 

[drf256]

This is a pretty ugly factory port roof isn’t it, do they all look like that on the 260’s? Don’t recall seeing any of the 024/026 cylinders I have had look like that.

Many do look like that. It’s not as noticeable as you would think until you magnify it. If it was another model, I’d grind that out, but in an 026 you don’t want to raise that roof up further.

The intake roof is similarly ugly.

If you look at those pics you’ll see where it’s widened and where I blended it to the factory roof. You can see the staining of the port in the center just distal to the inner port.

 

[drf256]

For sure you guys know way more about this than I do, and I greatly appreciate the ability to learn more from the gurus here.

This 024 AVS is the only chain saw I have ever owned, and has served me well for over 35 years. It's now way more powerful than it was new and runs perfect, thanks to your contributions, especially Doc's. Before the aftermarket P/C swap a few years ago and this recent upgrade, all I've ever done to it is replace a starting pawl and run it out of gas before it went back into the case, sometimes for a year or more before using again.

I'm happy to put a timing wheel on this if we think it will help understand what's going on. But a big part of me suggests leaving it alone and using it for the next decade or so, as I'm not sure it could be improved further for my intended use.

Santa is bringing me another dead West German 024 AV powerhead that I'll make into a 16" bar saw with some of the bits I have leftover from this upgrade. Anyone have a top and air filter cover in decent shape for one of these? Maybe I'll play with porting and timing on this one:

View attachment 358499

Looks like you’re asking the saw to do more than it was intended on doing. Also looks like you caught the bug, lolol.

IMHO, an 026 is a 16” saw. You could pull any bar with one, it’s just a matter of how effectively.

Generally, 50cc saws are 16”, 60’s are 20”, 70’s are 25-28”. Just where the sweet spot is for those saws, especially stock.

I’d leave your nice saw alone and play with your new one.

 

[drf256]

More port pics to illustrate.

The intake and exhaust roofs are STOCK.

44.7 260 jug.

 

[Paul Fithian]

Fun fact, Stihl advised the saw was built October 1985, five years before West and East Germany were combined.

 

[drf256]

Paul,

For the work you are doing, you should find a good old 036 or 044 and play with it.

50cc saws can do it, but 60-70cc saws can do it much faster and easier.

 

[Woodpecker]

Paul,

For the work you are doing, you should find a good old 036 or 044 and play with it.

50cc saws can do it, but 60-70cc saws can do it much faster and easier.

I was thinking the same thing Doc. Pretty hard to beat the classic 044, 024/6 combo.

 

[KcChiefs2019]

Paul,

For the work you are doing, you should find a good old 036 or 044 and play with it.

50cc saws can do it, but 60-70cc saws can do it much faster and easier.[/QU

Paul,

For the work you are doing, you should find a good old 036 or 044 and play with it.

50cc saws can do it, but 60-70cc saws can do it much faster and easier.

Them are some big logs for the smaller saw. But hat goes off to this guy for putting in the work on finding the little bit extra HP and CC’s to get it done
.

 

[Paul Fithian]

Had a look at timing numbers for this saw:
- Exhaust: 99
- Transfer: 120
- Intake: 71

Here's how it compares to the 024 AV I recently upgraded with a shaved and ported 44mm Mahle cylinder:

Maybe take the intake on this 024 AVS up to 76 or higher and make it run even better?