Rebuilding MS 440 Magnum

[Derek0525]

New here but need some help I have a bunch of downed trees on my property from a storm we had a few weeks ago so I was out cutting things up and was in the middle of limbing and the saw just died. I knew it just blew up so I took the muffler off and looked the rings look bad and the exhaust side of the piston looks pretty bad. So I found a rebuild kit online I'm guessing this is the one I need http://www.sawagain.com/meteor-stihl-044-ms-440-cylinder-piston-ring-assembly-12mm-pin/. Not sure if the link worked I looked at OEM Stihl but it was about $200 more. And what else should I look at or change wile I'm doing this? Also I noticed the decompress was pushed down which I'm guessing is why it blew.

[tlandrum]

I would not use the after market cylinder. take yours and clean it up then install a new meteor piston and caber rings. there is a huge quality and performance drop when you go after market on the cylinder. the meteor pistons are great though.

[Derek0525]

I have not taken it apart yet but if the cylinder is to bad is this the cylinder I need it doesn't say its for a 440 magnum not sure if it matters or not.
http://store.chainsawr.com/products/stihl-ms440-chainsaw-cylinder

[celliott]

Yes, that cylinder should work. There isn't really a difference between a MS440 and a MS440 magnum, besides the name.

Quite often, you can clean the cylinder up, as tlandrum said.
The cylinders have a nikasil plating which is very hard, and it probably isn't scratched. More likely, the piston transferred aluminum onto the cylinder wall when it got too hot. You can remove this aluminum using multiple methods. Muriatic acid and a 3M pad is one way. Gotta get all the aluminum off, so the inside of the cylinder is smooth- if it catches your fingernail, not good enough.

If you can salvage the cylinder, then you're only buying a piston and rings.

Keep in mind, if and when you do rebuild it, you have to figure out why it blew up in the first place. If you don't correct that problem, it'll just do it again.

Lots of information and knowledgeable people on this site- have questions, just ask 

[Derek0525]

I pulled it apart this morning I don't think the cylinder is salvageable it looks like the bottom ring broke it put a real deep gouge in the cylinder and the top of the piston and cylinder are beat to crap. Kinda figured it was bad when there was shavings in the muffler. What things should I check for as what caused the problem it did have a lot of hours on it I bought it from a logger about 5 years ago. I know that last year or so I would have to give it about 10-15 pulls to start it and it wouldn't want to stay idling if I set it down not sure if that had anything to do with it.

[Derek0525]

This is what it looked like

[Derek0525]

Well guess the pics didn't load

[Roundhead]

no offense but I disagree about aftermarket cylinders. not all are that bad. some are cheaply made but others are pretty good. I doubt most would recognize a power difference. by the time it takes to clean up a cylinder it may not be worth it. besides if he doesnt get it 100% clean he will scratch up his new cylinder. meteor and hyway are good aftermarket brands. just my 2 cents

[JT78]

Well to start need to.check the bearings make sure there is no play in them also change the crank seals and rebuilt the carb. Check to make sure there are no air leaks around carb intake. Don't know if baileys sells a woodland pro kit for that model heard good things about hyway also. Once you get it re assembled double check for air leaks and make sure you set the carb correctly.

[JohnG28]

Did the decomp valve come apart? You said it was pushed in, but is it still all there or no? If part of it came apart while running and dropped pieces into the running engine that could likely be the culprit that killed it.

[Derek0525]

Think I found the problem there were half moon dings all over the top of thepiston and the top of the ccylinder I can only see one keeper for the pin that holds the piston on and the side that is missing is the side where the ring and the cylinder wall is messed up.

[Weekend_Sawyer]

Derek, Pictures are easy to post here but you have to follow the procedure.

Take a look here
https://forestryforum.com/board/index.php/topic,61788.0.html

[Tom King]

Think I found the problem there were half moon dings all over the top of thepiston and the top of the ccylinder I can only see one keeper for the pin that holds the piston on and the side that is missing is the side where the ring and the cylinder wall is messed up.

I've had that happen.  I buy the cheapest cylinder kits, but buy, and only use, OEM wrist pin clips now.  I bought a Meteor cylinder kit once, but didn't find that the cylinder lasted any longer than the cheap Chinese ones off ebay.  But in fact, the Meteor cylinder was the one that got eaten by the malfunctioning clip, so it wasn't a fair test without an OEM wrist pin clip.  OEM clips are one part that is pretty cheap anyway.

[Derek0525]

Im guessing thats part of the keeper on the top on the exhaust side it looks like it was pounded into the top of the cylinder i tried to pry it out but it wont come out


 



 
missing keeper


 


 

[shawnspeed]

looks to me like the keeper came out and is embedded in the head... >:(good news is , it does not look like it gouged the upper cylinder where compression is built... 8)...gouges in the lower cylinder have not been a problem for me (20 + years of small motorcycle 2 stroke stuff, mostly 80cc)...I would replace the piston & rings, get that chunk of c-clip outta the head, and run it...New to this saw stuff, but not 2 strokes...silly question, but why don't you guys just have the cylinders re-plated???There are several companies that specialize in that on the motorcycle side...and a cylinder is a cylinder...just curious...Shawn

[Andyshine77]

looks to me like the keeper came out and is embedded in the head... >:(good news is , it does not look like it gouged the upper cylinder where compression is built... 8)...gouges in the lower cylinder have not been a problem for me (20 + years of small motorcycle 2 stroke stuff, mostly 80cc)...I would replace the piston & rings, get that chunk of c-clip outta the head, and run it...New to this saw stuff, but not 2 strokes...silly question, but why don't you guys just have the cylinders re-plated???There are several companies that specialize in that on the motorcycle side...and a cylinder is a cylinder...just curious...Shawn

The cost of re-plating the cylinder often costs the same as a new top end, so it's not cost effective. Motorcycle cylinders on the other hand are normally more expensive. Now when it comes to cylinders that are NLA it's the only option. I've also seen a few punched out chainsaw cylinders as well, but it's hard to do because the cylinder walls are thin, epically near the transfers.