Ms880 repair

[SteveSr]

One of the photos looks like a little transfer was left near the bottom of the jug. If that is transfer it needs to be cleaned up.

I didn’t clean it got so hot it cracked the strip of metal on the side. I was milling when it happened pushing it hard

What you have is thermal run-away. You may be able to monitor for this with a helper with a laser thermal monitor aimed at the cylinder looking for a rapid temperature increase. If the temperature doesn't level off you are headed towards another meltdown.

Pushing hard while milling is not generally a good idea. Did you use the proper chain for milling and have the oiler set properly? Was the chain razor sharp? You also need to learn how to properly tune the saw and make sure that it is running a bit on the rich side to keep it cool.

As you found out milling is terribly hard on a saw. Also breaking in a saw on a mill is not something that I would want to do. I would also strongly consider using only genuine Stihl OEM parts (like a new piston) instead of possible dodgy AM stuff. You may want to head over to the milling forum for more insight. MS880s are rare in this forum as most don't need to drop 6' DBH trees!

 

[MFV]

One of the photos looks like a little transfer was left near the bottom of the jug. If that is transfer it needs to be cleaned up.


What you have is thermal run-away. You may be able to monitor for this with a helper with a laser thermal monitor aimed at the cylinder looking for a rapid temperature increase. If the temperature doesn't level off you are headed towards another meltdown.

Pushing hard while milling is not generally a good idea. Did you use the proper chain for milling and have the oiler set properly? Was the chain razor sharp? You also need to learn how to properly tune the saw and make sure that it is running a bit on the rich side to keep it cool.

As you found out milling is terribly hard on a saw. Also breaking in a saw on a mill is not something that I would want to do. I would also strongly consider using only genuine Stihl OEM parts (like a new piston) instead of possible dodgy AM stuff. You may want to head over to the milling forum for more insight. MS880s are rare in this forum as most don't need to drop 6' DBH trees!

Yeah I got some thinking to do I need to order a pressure gauge and set up a rig to put this together and pressure test. Then I will figure out if it is a saw problem or a me problem. It was a crosscut chain but it could have been sharper. Mostly all we have here is hardwood and that’s mainly what I go after.

 

[MFV]

Yeah I got some thinking to do I need to order a pressure gauge and set up a rig to put this together and pressure test. Then I will figure out if it is a saw problem or a me problem. It was a crosscut chain but it could have been sharper. Mostly all we have here is hardwood and that’s mainly what I go after.

I also have seen people use thermocouples on them this could be an option also

 

[CausticUC]

I also have seen people use thermocouples on them this could be an option also

Slightly different purpose I would think; a thermocouple would sort of be a secondary cutout while milling. Something you would use after getting things sorted out.

Even then I wouldn't count on it to save you, thermocouple are on or off; no warning and no indicator.

You could however strap on a cheap temperature and rpm gauge. A live read of your rpm fluctuations is probably more valuable information than of temperature, after you have it setup.

It will reflected both your conscious and unconcious variance that is changing your feed rate. No matter the cutting device, there is an optimal feed rate for that wood type, push it beyond and the cutting chain/head/bit/blade will start converting the extra friction to heat on the cutting device, on a power head the rpm will drop slightly and your cylinder temperatures start to rise.

When milling, optimal feed rate = money! It saves you, your equipment and most importantly it saves you time. Time that you are not fixing/rebuilding something because it was pushed a bit too long or a bit too hard.

Your feed rate will also tell you your chain sharpness, when you start you should know how long it takes to go 1" or 1 foot. If it takes longer or your rpm drops, you are trying to compensate.

Sorry for the quasi-rant, I had the feed rate discussion a few times. For one guy to took two years to understand and a lot of broken equipment, and downtime that could have been avoided. If your milling you need to know and understand your feed rate and what its telling you.

 

[MFV]

Another good bit of advice makes sense. I have been cutting wood a long time but this is different to get used to

 

[SteveSr]

I also have seen people use thermocouples on them this could be an option also

These were at one time popular in the 2-stroke racing motorcycle environs. They were mounted in a big ring terminal that fit under the spark plug seat on top of the cylinder. Thermocouples are linear devices so should give you a good temperature reading to prevent another melt down. If you are doing a lot of milling this might be worth the investment until you learn the ropes.

 

[MFV]

These were at one time popular in the 2-stroke racing motorcycle environs. They were mounted in a big ring terminal that fit under the spark plug seat on top of the cylinder. Thermocouples are linear devices so should give you a good temperature reading to prevent another melt down. If you are doing a lot of milling this might be worth the investment until you learn the ropes.

Yes it could be I am an I/E tech so I am familiar with them I just didn’t expect to smoke a saw twice in 2 months I need to do something

 

[drf255]

Milling is super hard on a saw, but if you use some common sense its usually not deadly.

Ive used 40:1 Milling without detriment, but I have also run 24:1 as a safety. More oil helps, but heat is your enemy and all the oil in the world wont save you if yiu get too hot.

Whats the setup on the saw? How big of a bar? Did you mod the muffler? If you didn’t, its highly suggested if youre gonna mill, it helps the saw vent heat.

Make sure you know how to tune by ear. Set the saw fat and make sure it barely cleans up with pressure on the bar. Frequently unload saw in the cut and make certain its still burbling without pressure.

Like Steve said above, you better find out what toasted the last piston before it happens again. I’d also initially run that Saw in regular cuts and not milling, at least to find a decent tune. You could break in Milling, but you need to Be OCD about the tune. Hope you are using wedges behind the bar as you move along in the cut, that also helps to unload the saw a bit.

 

[Maintenance supervisor]

Could be I had it repaired at a shop they told me run it at 32/1 but it obviously wasn’t right it didn’t last a month

Rebuilding your own saws takes all the "what ifs" out of the equation.
Could be a simple crank seal, but unless you replace it ? Sometimes in a busy shop communication is lost and the left hand didn't tell the right.

 

[MFV]

Rebuilding your own saws takes all the "what ifs" out of the equation.
Could be a simple crank seal, but unless you replace it ? Sometimes in a busy shop communication is lost and the left hand didn't tell the right.

Well I didn’t find a ring compressor yesterday guess I will have to order one. I was looking at the anti rotation pins looks like they could be easy to mess up as well. But I will wait for my tools before I move forward.

 

[SteveSr]

Well I didn’t find a ring compressor yesterday guess I will have to order one.

I have never used a ring compressor. I have always been able to get my fingers in around and with the help of the chamfer on the cylinder got the jug on. You can also make a ring compressor out of a piece of plastic from a soda bottle or from an aluminum can. Do a search on the forum and you should get a lot of ideas.

I was looking at the anti rotation pins looks like they could be easy to mess up as well. But I will wait for my tools before I move forward.

This is another issue with AM pistons is that the ring locating pins can be loose and/or come out during operation. If this happens you toast a very expensive jug at a minimum assuming that the carnage doesn't get into the bearings. At a minimum you should verify that they are tight and firmly seated. Another good reason to use an OEM piston.

 

[Yukon Stihl]

Big zip tie for a quick ring compressor if you need one

 

[MFV]

Milling is super hard on a saw, but if you use some common sense its usually not deadly.

Ive used 40:1 Milling without detriment, but I have also run 24:1 as a safety. More oil helps, but heat is your enemy and all the oil in the world wont save you if yiu get too hot.

Whats the setup on the saw? How big of a bar? Did you mod the muffler? If you didn’t, its highly suggested if youre gonna mill, it helps the saw vent heat.

Make sure you know how to tune by ear. Set the saw fat and make sure it barely cleans up with pressure on the bar. Frequently unload saw in the cut and make certain its still burbling without pressure.

Like Steve said above, you better find out what toasted the last piston before it happens again. I’d also initially run that Saw in regular cuts and not milling, at least to find a decent tune. You could break in Milling, but you need to Be OCD about the tune. Hope you are using wedges behind the bar as you move along in the cut, that also helps to unload the saw a bit.

This saw is running a 64” cannon bar. I don’t know how to tune by ear this is the first saw I have had to work on. My muffler is just a hollow can with a screen on it clip on style. I put the top end back on it and checked compression 150 psi I think that’s low. Now I am trying to block of exhaust and carb to do some pressure testing and go from there

 

[Maintenance supervisor]

Lots of videos on tuning by ear, if you can't find one just let me know.

 

[MFV]

Lots of videos on tuning by ear, if you can't find one just let me know.

I will thanks. I pulled a vacuum on it last night it didn’t hold very long I am thinking of checking crankshaft seals

 

[cscltd]

The other problem I have seen with milling and lean out issues is running saw till runs right out of gas- that Last 30 secs it cuts real good, but temp really jumps on exhaust side of piston. Best to stop and refill before it runs out or at very least letup on throttle when you sense it is running out. That and pushing a dull chain is like being stuck in snow with throttle pegged- tires spinning engine screaming, transmission howling-something has to let go-usually piston scoring in chainsaw case

 

[MFV]

So I have new seals on the way I have never removed a clutch before. Can I just use a 21mm socket on this hex nut?

 

[cookies]

yes if you use a impact gun it will come off easily

 

[MFV]

yes if you use a impact gun it will come off easily

Regular threads ?

 

[cookies]

opposite of engine rotation..