MS260 Buy another or Repair?

[ChrisA]

New to the forum so I apologize if this is a repeat, I did a quick search prior to posting and didn't see anything.

This is my quandary, I have an older MS260 PRO from my FIL that was straight gased. I was standing right there when he did it, didn't know that he didn't put pre-mix in it and he went to sink into a huge piece of wood we were trying to split and it didn't last long at all. Piston melted a little piece to the cylinder wall, cleaned up the cylinder with muriatic acid but ultimately decided it was too scored to re-use.

I bought an ebay top-end kit and rebuilt it, one of the rings cracked a little when I was putting it on and I didn't think it would matter. Started right up and ran like a champ. Didn't want to over-do it so just let it run for about 15 minutes slowly revving it up. Killed it and let it cool down, repeated the same procedure and called it a night. Next day went to repeat and couldn't pull the cord, opened up muffler and literally pieces of the piston fell out of the exhaust port, it was totally ripped apart, like it had just exploded. Bought another top-end kit off ebay and replaced it, thinking that the cracked ring was the culprit. Same procedure, slowly broke-it in, let a full tank of 40:1 run through it with Stihl oil (rather than 50:1 which instructions call for). Used it to cut down several small trees no problem, ran like a champ. Sunk it into the first bigger tree (not even that big, probably 16" diameter). Stopped dead in it tracks, opened it up again and same thing, piston cracked.

Here are my options:

- Have access to OEM Mahle piston and cylinder through Stihl parts friend $190
- Craigslist gently used MS260 PRO $400 (for sale right now, but seems high, haven't looked at it yet)
- Meteor set for $150, or some other aftermarket???

I don't know what to do because I've seen so many people on the internet say that the ebay parts work fine, so that makes me wonder if something I am doing is wrong or if something else on the saw is messed up. The pistons have literally just fallen apart into pieces, which I assume is because they are cheap parts. Anyone else have this issue? Hate to buy new Stihl parts and have same thing happen...please help!

 

[cedarshark]

I believe your problem is the ebay kits. I know some folks here have good luck with aftermarket kits, buts I am not one of them. Meteor pistons are great but no one seems to know where the cylinders are made. I would either buy a used 260 Pro OEM cylinder and put a meteor piston in it or go all OEM. Just my 2 cents.

PS: I am fighting an 044 now with an A/M Chicom kit and its garbage....will go back to OEM.

 

[ChrisA]

Thanks for the reply - how much scoring is too much, I personally thought the OEM Mahle cylinder was good enough for reuse, but the Stihl dealer said no (obviously!!!). If I posted a picture do you think you would be able to tell?

 

[KG441c]

Buy my ported 026 in tradin post thats new top to bottom!! Lol

 

[Stihlofadeal64]

Sounds like a bad experience indeed. The "little crack" when you installed the top end sounds like trouble to me. To me the saw is definitely worth fixing, you just have to
be cautious as to how you install the kit. If I had the green backs for the Mahle kit, I'd pull the trigger on that set. The cost is less than the used MS260 pro you mentioned.
Since I'm not sure the source on the Ebay kit I'm not going to start to crap on the quality, but one I purchased was pretty much unusable. The ports were weird shaped, the
Nikasil was very sketchy -- not even worth trying. (I've personally repaired probably over 200 saws in this series o26, 026 pro, MS260 and MS260 pro, even the little 024).
If you do buy the OEM kit, take some time and replace the fuel line, filter and impulse (if you have not already) and do a pressure vac test before you run the saw. If not,
see if your Stihl parts friend can do it for you.

On another note, those like myself no nothing at this point as to how you tuned the saw. It could have died the last time due to lean seizure because of an improper tune.
Take some time and do some searches here on "tuning a saw" there is a great thread about that, and if you are in this thing to fix, repair and maintain your saws I suggest
you invest in a wireless TACH as well. Keep us posted on the choice and progress. Welcome to AS

 

[angelo c]

Thanks for the reply - how much scoring is too much, I personally thought the OEM Mahle cylinder was good enough for reuse, but the Stihl dealer said no (obviously!!!). If I posted a picture do you think you would be able to tell?

yes. post the cyl pics and the "formerly fuctioning" piston pieces as well.
we like pics.

 

[Stihlofadeal64]

Thanks for the reply - how much scoring is too much, I personally thought the OEM Mahle cylinder was good enough for reuse, but the Stihl dealer said no (obviously!!!). If I posted a picture do you think you would be able to tell?

Post the pics of the cylinder
I personally would not use acid. But others may chime in otherwise on their methods.
Would love to see the inside of your cylinder with good clear pictures.

 

[nstueve]

The problem that people can't rap their minds around is Cheap China cylinders. Many brands of AM cylinders have been used and many have problems. Even the better Hyway brand china cylinders yield lower compression than I would like to see. Another BIG problem with 95% of AM kits is the extremely cheap cast rings they use. Some also have an "out of round" problem where the machining didn't make the piston bore as true as the factory. Yea the piston and rings still fit but when you're talking thousandths here and there they all add up and even good rings can't covet those small imperfections up. Meteor, Ephesian(sp), Hyway, and OEM are all I put on. if its Hyway brand it still gets inspected and a set of caber rings.

Specifically on your 026 I would get an OEM cylinder or use the origional. And put a meteor piston and rings in it.

 

[KG441c]

Tecomec is another excellent cylinder/ piston kit

 

[MuskokaSplitter]

Ive had good and bad china cylinders. 044 runs like a beast and a husky 55 had some casting flaws...saw wouldnt run.


I try to clean up the original cyl. And use a good piston with caber rings.

Most have had great success with meteor.

Really depends on what u want to spend.

Post pics of your cylinder maybe its not ao bad.

I did my 038super with a tecomec piston and cleaned the cylinder. The cylinder was far from perfect but it runs well.

 

[ChrisA]

Intake side scoring

 

[ChrisA]

Exhaust side scoring

 

[ChrisA]

Another of exhaust - all of these pics are of the original MAHLE that was straight gased - I'll post pics tonight of the old piston and also of the other cylinders and pistons from the AM kits.

 

[nstueve]

Wouldn't run it like that. Needs to be clean and smooth. If you can run the metal tip of a screwdriver or scratch awl and feel the scoring, it shouldn't be used.

Also you should clean it with a split mandrel and emery paper. It won't hurt the cylinder. Hone clean with red scotchbrite and WD-40. You can use a brake cylinder hone to hold the scotchbrite to the cylinder and run it up and down to clean the walls up.

 

[ChrisA]

Will honing it scratch the nikasil? This is a 44mm, anyone have any luck boring out an OEM to the 44.7mm and just getting the larger piston, is that even possible? Same concern I have, would that chew through the nikasil, how thick is that lining?

 

[LogSawyer74]

I've bought several brand new OEM top end kits for the 260 on ebay for $159. Think there is at least one on there now..... But the weedeaterman site has meteor kits for sale (which I think are as good as OEM), and it looks like he just posted a discount code for 5% off. Great deal

 

[angelo c]

Will honing it scratch the nikasil? This is a 44mm, anyone have any luck boring out an OEM to the 44.7mm and just getting the larger piston, is that even possible? Same concern I have, would that chew through the nikasil, how thick is that lining?

no boring. honing just to remove the Al deposits.. check out the Al cleanup without acid posts. Mastermind has a good one.

 

[ChrisA]

no boring. honing just to remove the Al deposits.. check out the Al cleanup without acid posts. Mastermind has a good one.

Thanks - I read about honing on this site, this is another possibility. I'll post more pictures tonight and take everyone's suggestions.

 

[cedarshark]

I wouldnt hone it. Chips the Nikasil at the ports. Overboring will remove the thin coat of Nikasil and ruin the cylinder. I used muratic acid and q'tips for years with good success but now use a jewelers grinder and sanding wheels. Quicker but not necessarly better results. Your cylinder looks scored all the way around. It will take time and patience. if you have neither, buy another clean oem cyl and meteor piston. Be careful and measure your bore, some of the early 026pros had the smaller piston if I recall correctly. I just had to buy an 044 OEM used cylinder and piston ($115) so you can save some serious money by DIY. Lots of good folks here will help you along the way.

 

[fearofpavement]

Do you have some pics or a better description of "the piston broke"? Where did it break? Did you orient the piston in the correct direction? ie, arrow pointing towards the exhaust port?