Stihl 024 AV S Restoration Advice

ElZorro67 · February 16, 2021, 06:56:08 PM

Hello everyone, I'm a new member here smiley happysmiley I'm working on getting my late father's Stihl 024 AV Super back in shape. It served him well and I want to fix it up in memory of him. It won't start, and as suspected the piston and cylinder are badly scored and need replaced. I see there are quite a few 024 piston and cylinder kits available online, but I noticed in the manual that the 024 has a 30mm stroke and the 024 S has a 32mm stroke. Both have a 42mm bore. So what I'm trying to find out is if a 024 piston and cylinder kit will work, or if I need to get a kit that is specifically for the 024 S. Mostly I've seen 024 cylinder and piston kits. Some of them note that they won't work with a 024 S and some say they do, so it's been challenging to sort out. Any advice or suggestions on where I can find the correct replacement kit, or any tips for restoring the saw would be greatly appreciated.

Al_Smith · February 16, 2021, 07:04:07 PM

I was made aware the 024 and 026 models used three different muffler systems and two were very restrictive .The one I have bought from a dealers dead pile had a partly scorched exhaust side of the piston due in part to the most restrictive .About 10-15 minutes with a die grinder solved that problem . I've never done another thing to it and it runs like a top .

Al_Smith · February 16, 2021, 07:28:00 PM

From the parts list Stihl 024 crankshaft 1121 030 0400 fits 024 AVEQ and 024 AVEQW .Crankshaft 1121 030 0405 fits 024 AVSEQ and 024 AVEQWB .What all that means I have no idea but it only shows one piston .However it shows two cylinders Assuming one would be for the longer crankshaft throw which I have no idea what that is .

ElZorro67 · February 16, 2021, 08:00:16 PM

Thanks Al, I really appreciate it. That's interesting about the restrictive muffler, I noticed a lot of discoloration near the exhaust area indicating excessive heat that fits with what you're saying. I hadn't realized it was out of the ordinary and could be generating more heat than it should. The muffler is damaged so I'll replace that and when I do I'll have to investigate modifying it like you did.

That's good to know regarding the crankshaft and piston. It makes sense there would be 2 different cylinders and that fits with the information from the manual on page 48 about the stroke / displacement for the 024 compared to the 024 S https://m.stihlusa.com/WebContent/CMSFileLibrary/InstructionManuals/STIHL-MS-024-Owners-Instruction-Manual.pdf

If I could determine the part number for the original 024 S cylinder it would probably help narrow things down. I'll have to investigate further.

Al_Smith · February 17, 2021, 05:14:08 AM

If it helps I can get the two part numbers of the cylinders which are shown as a unit with the piston .It would stand to reason though if there is 2 mm difference in the stroke that with the wrong cylinder a spacer could be made which should work .It might be such a thing a spacer less than 2 mm could be used to raise the compression if so desired .Weather that would place the porting out of wack I'm not certain as I've never done it ,just a thought .
The only cylinder switch I've ever done on a Stihl was using an 036 cylinder and piston on an 034 .I'm not certain if that could be done using an 026 cylinder on an 024 or not .I'm sure somebody would know though .
They talk about using an 038 mag cylinder on an 038 AV but that is not as easy as just bolting it on .

Mad Professor · February 17, 2021, 05:29:30 AM

The 024S shares same crank/stroke with 026/260. I'd look for a good used Stihl 026/260 cylinder (44mm 026 or 44.7mm late 026, 260). There is currently a guy on ebay that has NOS/OEM Stihl 44.7mm pistons for $40 shipped. He had the 44mm pistons too, I got one for a straight gassed 026 I'm fixing.

Make sure of cylinder size when getting a piston and avoid chi-com junk. If you can't find OEM Meteor pistons are pretty good.

Do the crank seals, they come in Stihl gasket set. Flywheel side is known to leak on older 024/026/260 Stihls.

One other thought, how bad is your cylinder? Often you can clean them up and put a piston in if you don't want to put a 026/260 cylinder on it.

P.S. welcome to the forum

moodnacreek · February 17, 2021, 07:57:04 AM

My .o24 lost most of the frock on the air cleaner and scored the cylinder. This is the only chainsaw I ever ruined. I was given a 'parts' o24 that had a clean piston and cylinder and I put it on my block. The head of the piston hit the top of the cyl. head. Just had to grind a little off and away we go, that was at least 10 years ago.

Al_Smith · February 17, 2021, 11:05:30 AM

Like I said it was most likely the restrictive muffler that did some slight damage to mine but it didn't kill it .However being old school I run the oil /fuel ratio at 32 to 1 for extra lubrication and so far it's been a good little saw .Saying that I'm not certain if it's standard or super model .I need to get into my shed later so I'll take a peek see .

Al_Smith · February 17, 2021, 11:09:17 AM

Now then the 026 models .I've seen these things hot rodded and for little 3 cubers they can really carry the mail .I so far have not done that but I'd like to some day .Gotta find one first that doesn't cost a kings ransom ,stingy you know . :D

donbj · February 17, 2021, 03:02:43 PM

I have a couple of Stihls in the batch I gathered. I'll check when I get home later

donbj · February 17, 2021, 06:52:52 PM

It's an 028 Super. Good luck with your project

ElZorro67 · February 17, 2021, 08:36:20 PM

Quote from: Al_Smith on February 17, 2021, 05:14:08 AM
If it helps I can get the two part numbers of the cylinders which are shown as a unit with the piston .It would stand to reason though if there is 2 mm difference in the stroke that with the wrong cylinder a spacer could be made which should work .It might be such a thing a spacer less than 2 mm could be used to raise the compression if so desired .Weather that would place the porting out of wack I'm not certain as I've never done it ,just a thought .
The only cylinder switch I've ever done on a Stihl was using an 036 cylinder and piston on an 034 .I'm not certain if that could be done using an 026 cylinder on an 024 or not .I'm sure somebody would know though .
They talk about using an 038 mag cylinder on an 038 AV but that is not as easy as just bolting it on .

Thanks again, it's good to know there are different options for fixing it. I think I figured out the part number for the cylinder from the list Med Professor attached. That's an interesting idea about the spacer, I hadn't realized that could be a possibility. What you mentioned about the restrictive muffler really fits with what I'm seeing with my 024 S. And I'll make a note to remember to adjust the mix so it has better lubrication.

ElZorro67 · February 17, 2021, 08:56:32 PM

Quote from: Mad Professor on February 17, 2021, 05:29:30 AM
The 024S shares same crank/stroke with 026/260. I'd look for a good used Stihl 026/260 cylinder (44mm 026 or 44.7mm late 026, 260). There is currently a guy on ebay that has NOS/OEM Stihl 44.7mm pistons for $40 shipped. He had the 44mm pistons too, I got one for a straight gassed 026 I'm fixing.

Make sure of cylinder size when getting a piston and avoid chi-com junk. If you can't find OEM Meteor pistons are pretty good.

Do the crank seals, they come in Stihl gasket set. Flywheel side is known to leak on older 024/026/260 Stihls.

One other thought, how bad is your cylinder? Often you can clean them up and put a piston in if you don't want to put a 026/260 cylinder on it.

P.S. welcome to the forum

Thanks Mad Professor I really appreciate your insights and it's nice to be welcomed as member of the forum. That's great to know I could swap out the cylinder and piston for an 026/260. $40 sounds like an excellent price for OEM, I'll have to check it out. That's a good question about the cylinder condition, and I was wondering about it too. And by the way, a BIG thanks for attaching the factory parts list and shop manual! Those will be extremely useful.
I attached a few pics of the cylinder and piston. As you can see the piston is pretty much trashed. The damage to the cylinder seems to be mainly on the exhaust side and the worst of it is just below the exhaust port. The intake side seems fairly good and overall it's fairly smooth except for the rough area below the exhaust. I don't know enough about cylinders to know how much damage is too much or if this could be fixed up. I did my best to take clear pics, so with any luck that will give some idea of what it looks like.

ElZorro67 · February 17, 2021, 08:58:10 PM

Quote from: moodnacreek on February 17, 2021, 07:57:04 AM
My .o24 lost most of the frock on the air cleaner and scored the cylinder. This is the only chainsaw I ever ruined. I was given a 'parts' o24 that had a clean piston and cylinder and I put it on my block. The head of the piston hit the top of the cyl. head. Just had to grind a little off and away we go, that was at least 10 years ago.

That's a shame, but at least you could fix it up and it's still going after 10 years. It makes me wonder if that could have been what happened to dad's 024 S.

ElZorro67 · February 17, 2021, 09:00:28 PM

Quote from: donbj on February 17, 2021, 06:52:52 PM
It's an 028 Super. Good luck with your project

Thanks donbj I appreciate that, and thanks for the pic, that looks like about the same era as the 024 S judging by the cover design and "electronic quickstop". There was a nice "Stihl Made in West Germany" badge/plate on the recoil cover of the 024 S, but the paint has mostly worn off. Luckily I managed to find a replacement vinyl sticker for it on eBay.

donbj · February 17, 2021, 09:57:35 PM

Wow, certainly that piston is toast! That cylinder though my novice opinion says it can be brought back. The cross hatching is still visible in most of it. That's a start. I'm very curious as to what some of the more knowlegeable say regarding that as I am in a learning curve with these two stroke saws.

Mad Professor · February 17, 2021, 10:04:35 PM

Quote from: ElZorro67 on February 17, 2021, 08:56:32 PM
Quote from: Mad Professor on February 17, 2021, 05:29:30 AM
The 024S shares same crank/stroke with 026/260. I'd look for a good used Stihl 026/260 cylinder (44mm 026 or 44.7mm late 026, 260). There is currently a guy on ebay that has NOS/OEM Stihl 44.7mm pistons for $40 shipped. He had the 44mm pistons too, I got one for a straight gassed 026 I'm fixing.

Make sure of cylinder size when getting a piston and avoid chi-com junk. If you can't find OEM Meteor pistons are pretty good.

Do the crank seals, they come in Stihl gasket set. Flywheel side is known to leak on older 024/026/260 Stihls.

One other thought, how bad is your cylinder? Often you can clean them up and put a piston in if you don't want to put a 026/260 cylinder on it.

P.S. welcome to the forum
Thanks Mad Professor I really appreciate your insights and it's nice to be welcomed as member of the forum. That's great to know I could swap out the cylinder and piston for an 026/260. $40 sounds like an excellent price for OEM, I'll have to check it out. That's a good question about the cylinder condition, and I was wondering about it too. And by the way, a BIG thanks for attaching the factory parts list and shop manual! Those will be extremely useful.
I attached a few pics of the cylinder and piston. As you can see the piston is pretty much trashed. The damage to the cylinder seems to be mainly on the exhaust side and the worst of it is just below the exhaust port. The intake side seems fairly good and overall it's fairly smooth except for the rough area below the exhaust. I don't know enough about cylinders to know how much damage is too much or if this could be fixed up. I did my best to take clear pics, so with any luck that will give some idea of what it looks like.

That is aluminum transfer from the piston on the ex side of the cylinder. You should be able to clean that off with some careful polishing or using hydrochloric acid/muriatic acid . Hopefully the nikasil cylinder lining is O.K. under the transfer. You need to get all the transfer off.
If you use the acid you have to be careful not to get it on parts of the aluminum cylinder itself (port edges, or any nicks/scores through the thin lining), but it will dissolve the transfer. Wet/dry sand paper with some dish detergent/water will also take it off but don't use too coarse of paper and again don't hurt the port edges.
You can use both methods together. The acid will bubble as it dissolves the aluminum transfer. Sometimes there will be oily or carbon deposits in the transfer so you need to sand that off to let the acid get at the aluminum. Q-tips are a good way to apply the acid.
If you use acid be careful wear gloves and safety glasses. Have water to rinse things and baking soda solution to neutralize the acid.
I think the 42mm 024 pistons are still available from Stihl (pricey) and Meteor makes them also.

ElZorro67 · February 18, 2021, 01:57:34 AM

Quote from: donbj on February 17, 2021, 09:57:35 PM
Wow, certainly that piston is toast! That cylinder though my novice opinion says it can be brought back. The cross hatching is still visible in most of it. That's a start. I'm very curious as to what some of the more knowlegeable say regarding that as I am in a learning curve with these two stroke saws.

Oh yeah, toast is a great description for that piston - it sure isn't pretty. With any luck I'll be able to clean the cylinder walls and get it back in shape (fingers crossed).

ElZorro67 · February 18, 2021, 02:05:43 AM

Quote from: Mad Professor on February 17, 2021, 10:04:35 PM
Quote from: ElZorro67 on February 17, 2021, 08:56:32 PM
Quote from: Mad Professor on February 17, 2021, 05:29:30 AM
The 024S shares same crank/stroke with 026/260. I'd look for a good used Stihl 026/260 cylinder (44mm 026 or 44.7mm late 026, 260). There is currently a guy on ebay that has NOS/OEM Stihl 44.7mm pistons for $40 shipped. He had the 44mm pistons too, I got one for a straight gassed 026 I'm fixing.

Make sure of cylinder size when getting a piston and avoid chi-com junk. If you can't find OEM Meteor pistons are pretty good.

Do the crank seals, they come in Stihl gasket set. Flywheel side is known to leak on older 024/026/260 Stihls.

One other thought, how bad is your cylinder? Often you can clean them up and put a piston in if you don't want to put a 026/260 cylinder on it.

P.S. welcome to the forum
Thanks Mad Professor I really appreciate your insights and it's nice to be welcomed as member of the forum. That's great to know I could swap out the cylinder and piston for an 026/260. $40 sounds like an excellent price for OEM, I'll have to check it out. That's a good question about the cylinder condition, and I was wondering about it too. And by the way, a BIG thanks for attaching the factory parts list and shop manual! Those will be extremely useful.
I attached a few pics of the cylinder and piston. As you can see the piston is pretty much trashed. The damage to the cylinder seems to be mainly on the exhaust side and the worst of it is just below the exhaust port. The intake side seems fairly good and overall it's fairly smooth except for the rough area below the exhaust. I don't know enough about cylinders to know how much damage is too much or if this could be fixed up. I did my best to take clear pics, so with any luck that will give some idea of what it looks like.

That is aluminum transfer from the piston on the ex side of the cylinder. You should be able to clean that off with some careful polishing or using hydrochloric acid/muriatic acid . Hopefully the nikasil cylinder lining is O.K. under the transfer. You need to get all the transfer off.
If you use the acid you have to be careful not to get it on parts of the aluminum cylinder itself (port edges, or any nicks/scores through the thin lining), but it will dissolve the transfer. Wet/dry sand paper with some dish detergent/water will also take it off but don't use too coarse of paper and again don't hurt the port edges.
You can use both methods together. The acid will bubble as it dissolves the aluminum transfer. Sometimes there will be oily or carbon deposits in the transfer so you need to sand that off to let the acid get at the aluminum. Q-tips are a good way to apply the acid.
If you use acid be careful wear gloves and safety glasses. Have water to rinse things and baking soda solution to neutralize the acid.
I think the 42mm 024 pistons are still available from Stihl (pricey) and Meteor makes them also.

That's good to hear and know for the future in case I ever encounter a similar situation. I've tinkered with a fair amount of small engines over the years, but usually more basic troubleshooting, so I have a lot to learn when it comes to understanding how to approach things like this. I appreciate you taking the time to explain so well what steps I need to take in order to carefully clean it. I looked in my supplies and I have some muriatic acid here as well as the gloves, goggles, sandpaper, detergent and baking soda. I'm thinking I'll gently but thoroughly clean the entire cylinder first so there won't be any leftover oil or grease lurking, then prep everything for removing the transfer and very slowly, carefully start with the acid. Once I make some progress with it I'll post it here.
I came across some Meteor pistons for sale online, so once I make some progress with the cylinder and as long as it still looks like it's in good enough shape to reuse, I'll order one.

Mad Professor · February 18, 2021, 02:19:18 AM

Try to find out what caused the scoring or it could happen again:

air leak (seals, impulse line, intake boot)

lean mixture (carb setting/internals , fuel filter/line)

straight gassed

Guydreads · February 18, 2021, 02:43:52 AM

I would say no oil in the gas, based on the fact that there is only scoring on the exhaust side. That's what I've always heard. Maybe I'm wrong though.

ElZorro67 · February 19, 2021, 09:30:58 AM

Quote from: Mad Professor on February 18, 2021, 02:19:18 AM
Try to find out what caused the scoring or it could happen again:

air leak (seals, impulse line, intake boot)

lean mixture (carb setting/internals , fuel filter/line)

straight gassed

I started working on the cylinder the other day and the transfer was coming off slowly but steadily with the muriatic acid. Unfortunately a couple of the more damaged areas just under the exhaust port had apparently worn through the nikasil lining, and once the transfer aluminum was removed it started to pit a little.
Thanks again, I'll investigate for an air leak or any issue with the mixture / line / and put on a new fuel filter. I'm fairly certain it wasn't straight-gassed, since my dad was the only owner and wouldn't have done that. The air filter was looking rough, so I've wondered if something could have slipped by it.
I'm not planning on really using the 024 S once it's fixed and finished, since it's more of a sentimental thing, and I have a Husky 372 that I use instead. So the 024 S doesn't have to be running perfectly, but I'd like to have to have it running. Odds are once I get it finished it'll live on the shelf in the workshop most of the time.

Al_Smith · February 19, 2021, 12:05:12 PM

If the flaking is below the ring travel I wouldn't be real concerned about it .Even if just don't get stingy with the mix oil and it may never give you a problem .

ElZorro67 · February 22, 2021, 08:05:54 PM

Quote from: Al_Smith on February 19, 2021, 12:05:12 PM
If the flaking is below the ring travel I wouldn't be real concerned about it .Even if just don't get stingy with the mix oil and it may never give you a problem .

Thanks again, I appreciate your mentioning that. I hadn't thought as much about the location of the pitting. I measured and compared it to the ring travel and at it's lowest point of travel the top ring is roughly even and slightly above one of the pits, and the rest of the pits are just below that. When I make some mix for it I'll add more oil than usual. I've been using some retrobright to remove the yellowing on the plastic parts and that's done now, so I'm starting to put some of the saw back together.