MS 660 rebuild advice

[Fnkfab]

Yes, get into that saw and replace those parts mentioned above. I would avoid any aftermarket fuel lines, piston/cylinders, and more.
That cylinder- if the plug is loose and the threads are jeopardized, it should be fixed. Timesert insert or welding/retapping are the best options.
Meteor pistons are ok for this series- check what bore diameter you have since the original cylinder could have been replaced.

On this series, check the crank for play (wiggle it on both sides) and look carefully at all AV mounts.

How do we feel about aftermarket flywheels? Mine is the plastic fan kind, missing 6 blades.

 

[BuckthornBonnie]

Used OEM from here or eBay is a better option. The AM flywheels have been running in the clone saws, but I wouldn’t install one on a work saw.

Why so many broken fins??

 

[Fnkfab]

Used OEM from here or eBay is a better option. The AM flywheels have been running in the clone saws, but I wouldn’t install one on a work saw.

Why so many broken fins??

I can only assume the previous owner dropped it out of a tree when running. Carb box cracked, clutch plate cracked, flywheel upper AV mount (metal part) snapped in half...
These seem to be made of gold. Cheapest used ones Ive found are $130+.

 

[Fnkfab]

I can only assume the previous owner dropped it out of a tree when running. Carb box cracked, clutch plate cracked, flywheel upper AV mount (metal part) snapped in half...
These seem to be made of gold. Cheapest used ones Ive found are $130+.

Found a used oem for $75 shipped... just ordered, we'll see how it works out.

 

[Mad Professor]

Well the feeler gauge set i picked up had the smallest one at .0015" and there was no getting that in there.
So im going to go ahead and keep the P/C here.

Regarding replacing the jug seal. It looks like the cylinder comes off OK with a couple stihl tools ("assembly drift" 1111 893 4700 and circlip "installing tool 5910 890 2212"). The first is cheap enough, but the second looks to be $120. I guess i'll meander down to the local shop/dealer and see if they can timesert the cylinder and drop a new gasket in for me.

You need to gently slide the feeler gauge between the piston cylinder and the skirt. It will help to have a bit of the skirt sticking out below cylinder, and a film of mix oil on things. Be careful not to mar piston. 0.0015" should fit, >0.003" won't unless some wear

 

[Mad Professor]

Well the feeler gauge set i picked up had the smallest one at .0015" and there was no getting that in there.
So im going to go ahead and keep the P/C here.

Regarding replacing the jug seal. It looks like the cylinder comes off OK with a couple stihl tools ("assembly drift" 1111 893 4700 and circlip "installing tool 5910 890 2212"). The first is cheap enough, but the second looks to be $120. I guess i'll meander down to the local shop/dealer and see if they can timesert the cylinder and drop a new gasket in for me.

You can remove and install the piston/wrist pin without the special tools, stuff a rag/paper towel in crankcase in case circlips pop out. Buy an extra circlip or two, when they pop out they often fly to places unknown.

 

[Fnkfab]

You can remove and install the piston/wrist pin without the special tools, stuff a rag/paper towel in crankcase in case circlips pop out. Buy an extra circlip or two, when they pop out they often fly to places unknown.

^Thanks for that encouragement! Piston is off the saw-- no circlips harmed or lost in the removal. Deep socket makes a good stihl "assembly drift" tool.
I did this because i really want to take a closer look at the P/C fit. It is really snug. By my eyes, < 1thou, maybe 1/2 a thou. I would even argue that the visible wear might be related to this. I'm wondering if maybe they aren't a matched set? They are both stihl parts.

More photos.

 

[Mad Professor]

^Thanks for that encouragement! Piston is off the saw-- no circlips harmed or lost in the removal. Deep socket makes a good stihl "assembly drift" tool.
I did this because i really want to take a closer look at the P/C fit. It is really snug. By my eyes, < 1thou, maybe 1/2 a thou. I would even argue that the visible wear might be related to this. I'm wondering if maybe they aren't a matched set? They are both stihl parts.

More photos.

Maybe it's just the picture, but it looks like you are using two feeler gauges, the 0.0015", and a 2nd one, maybe the 0.002" (next in the set?). , 0.001" or less the saw would seize when piston warms up. Also measure at the center of the skirt, that is where wear occurs on piston

If you don't have mics, a machine shop would probably measure that up for free. Piston looks to be in good shape, put in a set of rings. Don't reuse circlips, they cost about $1.

Stihl pistons and cylinders should both be stamped for size, look for an "A" or "B" on piston crown and top of cylinder. Replacement pistons may be stamped "A/B"

 

[Fnkfab]

Maybe it's just the picture, but it looks like you are using two feeler gauges, the 0.0015", and a 2nd one, maybe the 0.002" (next in the set?). , 0.001" or less the saw would seize when piston warms up. Also measure at the center of the skirt, that is where wear occurs on piston

If you don't have mics, a machine shop would probably measure that up for free. Piston looks to be in good shape, put in a set of rings. Don't reuse circlips, they cost about $1.

Stihl pistons and cylinders should both be stamped for size, look for an "A" or "B" on piston crown and top of cylinder. Replacement pistons may be stamped "A/B"

ugh. you are right.
rookie guy and a new tool...didn't realize they were stuck together. in the center, its between .003 and .004.
Replace rings and run it? Or drop a meteor kit in there?

On a sidenote, I'm not sure what size or A/B info i can extract from the stuff stamped/forged/cast into the part.. i'm grasping at straws here. Maybe this makes sense to you guys:
Cylinder has:
1122 Stihl on the side
SK logo? 102 and 1B on the side
P16M SK logo? on the top
P followed by some sort of dot grid.

Piston has the following inside:
49 (appears to be the height)
052 701 2811 (2811 is lower but they seem connected?)
2 SK logo?
Stihl

 

[SteveSr]

Good call here. So this is my first time with a saw open... so bear with me:

Turns out this is the OEM stihl ms660 cylinder. ( guess that explains why i didn't think the saw felt under powered, being an MS650 and all.)
When i look in the cylinder i see some wear but my gut feel is this is OK. No deep scoring/scuffing.
The top of the piston has some charred stuff on it but otherwise looks pretty good from my eyes.
The piston seems tight on the crank. The crank can slide side to side down in the case-- looks like .050" play.

Questions:

1. Do i keep the piston and cylinder or swap for a meteor? (leaning towards keep)
2. Can i re-use the cylinder gasket? My guy feel is no but its tempting to just put it back together.
3. Anything else jump out at you guys?

What's going on with either side of the intake port? Need better lighted in focus pics to really see anything. Clean it up a bit with some red scotchbrite and rinse with brake cleaner so you can see what is really there.

 

[jimbo1490]

The decompression valve is often overlooked. Be very wary of a decomp valve that shows any wear, especially looseness. I've just finished rebuilding a ms441 which had a deep gouge in the original cylinder. I wondered what made that gouge and suspected maybe a broken spark plug insulator as I have seen that particular failure a couple of times before. I pulled the very very loose and worn decompression valve out of the original cylinder and took a close look at it and there you go: a little triangle shaped piece chipped out the edge of the valve. Thatll make a nice gouge!

 

[Fnkfab]

Maybe it's just the picture, but it looks like you are using two feeler gauges, the 0.0015", and a 2nd one, maybe the 0.002" (next in the set?). , 0.001" or less the saw would seize when piston warms up. Also measure at the center of the skirt, that is where wear occurs on piston

Any thoughts on the .003-004" gap?

What's going on with either side of the intake port? Need better lighted in focus pics to really see anything. Clean it up a bit with some red scotchbrite and rinse with brake cleaner so you can see what is really there.

Sorry-- photos inside things are hard. Reflections and lighting. Prob best i can do.

The decompression valve is often overlooked. Be very wary of a decomp valve that shows any wear, especially looseness. I've just finished rebuilding a ms441 which had a deep gouge in the original cylinder. I wondered what made that gouge and suspected maybe a broken spark plug insulator as I have seen that particular failure a couple of times before. I pulled the very very loose and worn decompression valve out of the original cylinder and took a close look at it and there you go: a little triangle shaped piece chipped out the edge of the valve. Thatll make a nice gouge!

Crazy! Per my post above, the decomp valve was toast, so its been removed and I've got a new OEM one in hand.

 

[SteveSr]

Sorry-- photos inside things are hard. Reflections and lighting. Prob best i can do.

No excuses - Don't be lazy... get a flashlight in there while taking the photo.

 

[Fnkfab]

No excuses - Don't be lazy... get a flashlight in there while taking the photo.

Let's be pretty clear on something-- I'm not lazy and those aren't excuses. I was doing my best to be polite. I work a full time job, have two very young kids, and spend my early mornings 5am-6am working on projects like this.

That said, i have since washed the parts and I'll happily snap another photo when i'm back to the shop for people on here to look at with the parts clean. Can't promise much better lighting since that was with a bright flashlight and the camera in there already-- but we'll see what we get.

 

[SteveSr]

Let's be pretty clear on something-- I'm not lazy and those aren't excuses. I was doing my best to be polite. I work a full time job, have two very young kids, and spend my early mornings 5am-6am working on projects like this.

That said, i have since washed the parts and I'll happily snap another photo when i'm back to the shop for people on here to look at with the parts clean. Can't promise much better lighting since that was with a bright flashlight and the camera in there already-- but we'll see what we get.

I didn't mean to be insulting but we can't help you if we can't see what is going on.

 

[Fnkfab]

OK-
So some progress made here. I ended up replacing the P/C with meteor and using new OEM piston rings. It's noteworthy that the OEM rings are black (i assume this is an oxide coating) and are noticeably stiffer.
I haven't given up completed on the old P/C but i haven't got them measured yet-- but figured they weren't new and needed to be thread repaired anyways so i set them aside for now. I tried taking photos but couldn't get anything better than i already posted.

I got the saw back together-- compression before firing it up was ~ 140psig. I assume the rings take time to seat. Prior to this teardown, my compression was 120 psig.
I haven't touched the carb screws yet-- it starts OK and seems to run fine but i haven't cut anything yet. I have a max flow on order and will be porting the muffler cover.

It took some work to get it started the first time. Thinking maybe i had put too much oil in when i was assembling the P/Cor things just needed to be fired once. I ended up using some starter spray for the first firing-- it coughed some black smoke, and then settled in to a nice idle. It fired up nice and quick with no issues 18hrs later. Funny thing happened to me--- i ran it WOT for a min or two and have the screws that held down the recoil starter plate unthread and come up. Those will be getting some thread lock and a torque wrench shortly.

I do have one other issue though-- the saw is now spraying quite a bit of what appears to be bar oil. Its coming out a few different parts of the chain guard. Any thoughts on this? Maybe i just cleaned it up and unclogged it and need to turn the oiler down? Or maybe the clutch cover s sitting funny? I had to pull that to replace the flywheel.

 

[BuckthornBonnie]

Good job getting it running.
Fix that OEM cylinder and run it with a new piston or that meteor. You’ll see a difference.
No need for starting fluid in two strokes.
Bar oil? From...?
Bolts and holes should be clean and torqued appropriately. Save the Loctite for coils screws, muffler bolts, some cylinder screws, and maybe problem areas.

 

[Totembear]

I would have tore down that saw and replaced bearings. That saw looks like it has been rode hard and put away wet. If you're going to use it for milling, thats some of the hardest work a saw will do. Anything that is suseptable to go wrong will with milling. But, just run it and keep your ears and eyes open. If it was just bucking I wouldnt give it a second thought.

 

[Fnkfab]

Bar oil? From...?
Bolts and holes should be clean and torqued appropriately. Save the Loctite for coils screws, muffler bolts, some cylinder screws, and maybe problem areas.

Well-- after closer inspection i see the threads on the case are actually pretty stripped. I must have lost the last couple on this last install. I'm going to order a helicoil kit and try my luck there.. ugh.

And as for the bar oil it was just more or less spewing out everywhere from under the chain cover. i decided to take the clutch off and have a look.

I had some trouble lining up the clutch cover with the spring earlier but didn't think too much about it. I just pulled the clutch-- oil pump spring is snapped on the end so it wasn't ever engaging the clutch cover. Maybe it was flopping around and leaking that way. I'll replace and put back together and see where we are at. I'll upload some photos later--- internet connection is bad this AM.

I would have tore down that saw and replaced bearings. That saw looks like it has been rode hard and put away wet. If you're going to use it for milling, thats some of the hardest work a saw will do. Anything that is suseptable to go wrong will with milling. But, just run it and keep your ears and eyes open. If it was just bucking I wouldnt give it a second thought.

100% agree-- it was my first time opening a saw up so i wasn't sure what to expect. What's a saw sound like when the bearings go?

 

[Mad Professor]

It won't pump oil with the drive spring not connected to the clutch drum, unless debris or broken parts are jammed up making the spring/pump turn. If that was the case your chain would be spinning all the time even at idle.

Have a look at the oil line from the pump to the oil outlet in the case. You'll need to pull the clutch off. Need to anyway to replace drive spring.