MS 660 rebuild

SeanKroll

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Olympia, WA
My cylinder is scored.

Supposedly, per the Stihl dealer cert'ed mechanic, due to lean conditions from a faulty decomp valve.

Seems to me the decomp is crisp and snappy, not at all showing issue.

The carb is old; I know the saw has not had any repair in 5 years of my ownership. My friend sold it to me, not having said the carb had any work in his time with it (maybe bought new, maybe not). I guess he had it a few years, possibly 5 or more.

Is a faulty carb a likely candidate for the lean condition?

Is the scoring on the wall from the broken piston ring scratching?


What is the minimum cost for a good cylinder and piston and whatnot to get it running?

If I send it off to be built for $250, seem like I wouldn't have to do any work, just buy parts and labor.

Driving distance to the saw builder, if desired, might take more than one saw.


What would you do, with a 661 being about $1200 plus tax.
 
I would get a new one, myself. For pro use new is the way IMO. You've got old everything in that old saw, including vibration mounts. I'd buy new and enjoy a smooth running new saw and the write off. Better yet, buy new and have it modded.
 
Or if you're getting some all-orange gear, you could go 395XP.

A couple more parts ones are listed that would just need some housing replacements for $500-ish (probably go a bit higher in the next 2 days.

We've demoed the Echo CS-800P (80cc) and it's no slacker -- rips pretty impressively for the $800 range!
 
I think they get scored with age as the P/C wear out; they get looser faster until compression feels like it is still enough, but most of the mix blows by during the compression stroke with the rest blowing by during ignition, so there's nothing left to push the piston down.

I'd just look for a great condition used 660 or get a new 390, 2188, or 395.
 
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  • #6
What is involved in it. I can turn a wrench, if I know what to do. Seems like its not a huge investment for a P and C.


How does one test the carb to avoid a problem if that is what caused lean conditions? Could just be wear, but you don't need a 660 most of the time, and he had an 044. I've done some work with it, but not tons. No hour meter. Would hate to find out its a carb problem with the new parts, and cook them.
 
If it was my saw, that being belonging to a retired fellow with plenty of time on his hands who can turn a wrench right well, but does not need a reliable saw with a long life ahead of it to make his daily bread...I'd rebuild it myself.

But in your shoes Sean, I think I'd just buy a new one and sell the old husk for what you can get to someone in a position to mess with it, to offset the new saw cost a little.

It's a small cost relative to your overall operating overhead, I'd hope.
 
  • Thread Starter Thread Starter
  • #9
Ya, seems to be the best course of action.

Parts saw.

I have no time. I'm interested to learn to rebuild, but I'm interested to learn so much.

Need to get a new saw and have it built.

Past the patch up small equipment phase.
 
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  • #12
Like Peter said, Slovaks are the most resourceful or smartest poor people on the planet.

My family had come up from my great grandfather shoveling coal in a furnace when he 'came over'.

My dad used to fix or save things when he could.
Very miserly.

Not a business owner. The idea of wear it out and but another was not taught to me.

People often love their older saws for grunt.

Lots want their 066 over a 660 over a...

My mini was the most expensive thing I've ever bought, new, and second overall to my house. It's been a slew of problems. New is untested in the field.

Still looking at new.

If I could swap bars and chains easily, I'd consider a Husky, maybe 3120.
 
My mini was the most expensive thing I've ever bought, new, and second overall to my house. It's been a slew of problems. New is untested in the field.
I'd like to hear more about your experience with Boxer. I saw August demoing one before his Vermeer -- it looked hulky/bumbly in backyard tree work. A Boxer mini recently went in our area at an equipment place for $10K -- another tree competitor got it. We've demoed a Ditch Witch (was just dandy), but we wanting to rent a Vermeer 625 or CTX100 at the next opportunity for a job, so as to really try it out before doing a serious search & purchase of one unit or another.

If I could swap bars and chains easily, I'd consider a Husy, maybe 3120.
We still have a 3120XP on our bucket list, but now have the realization that it's "only" 118cc and Husqvarna only recommends up to a 42" bar, which means our 395XP at 95cc and 36" bar is actually the sweet spot in the power/performance/cost equation.

(Sorry for the quotes, Boss :D)
 
I?m with the buy a new one school of thought, get the old one ported for shits and giggles.

Being tight-fisted costs money in the end.
 
I guess going from logging to arb work gave me a different perspective. Saws were always a tool to be used and abused. Saws should never be 'giving grief' in the field. If they are you don't have enough of them. Toss it aside and pull another one off the truck. I had I think 25 saws when I sold my business? One crew. We rolled with five to eight saws a day, depending if one or two trucks went. Big wood job? Modded 660, 066, and three 46/460s would be coming out to play and maybe the 880 if it was truly big wood. Minimum of two 200's going out each day and if there was even the slightest doubt of the performance of one of those 200's throw a third one in just in case.

Getting held up on jobs because of a saw when you're a tree worker makes no sense to me at all. Frigging around with saws is meant for the shop, not for on the job.

Once you get sentimental about a saw it's no longer a tool it's a collectors item.
 
I was never a fan of the 660, it never equaled the 066. If you buy new, you will have a 661, which is a big improvement from what people tell me
 
I agree with everyone. I'll PM you my address and I'd be happy to save you from that junk...
Shoot, if it were mine to give, I'd send you the 020 we have laying around. But I think we're wanting to take it back to the saw shop and make them stand behind it (bought it 6 months ago, leans out, doesn't run).
 
Sean, last I checked a few months ago it would be about $1300 US, PHO, but shipping would kill that even more.

Thanks for the thought, GP!
 
  • Thread Starter Thread Starter
  • #22
$1800 plus tax I think with b/c around here.
Possibly with the half-wrap handle, too.
 
My cylinder is scored.

Supposedly, per the Stihl dealer cert'ed mechanic, due to lean conditions from a faulty decomp valve.

Seems to me the decomp is crisp and snappy, not at all showing issue.

The carb is old; I know the saw has not had any repair in 5 years of my ownership. My friend sold it to me, not having said the carb had any work in his time with it (maybe bought new, maybe not). I guess he had it a few years, possibly 5 or more.

Is a faulty carb a likely candidate for the lean condition?

Is the scoring on the wall from the broken piston ring scratching?


What is the minimum cost for a good cylinder and piston and whatnot to get it running?

If I send it off to be built for $250, seem like I wouldn't have to do any work, just buy parts and labor.

Driving distance to the saw builder, if desired, might take more than one saw.


What would you do, with a 661 being about $1200 plus tax.

Certified or not is not so important. Not sure why that is mentioned every were. To me that means he is done the school, not the work and experience.

It will likely not run lean for a faulty valve. It will loose compression and if run a length of time it will most often get plugged.
Carb fault is can cause of scoring. Not as common as over heating from dull chains and over loading saw, but yes it happens. Usually noticed in performance of saw before this.
Scoring on the wall is usually aluminum from piston. As it melts the heat it sticks to the wall.
Piston rings can cause scoring if it break up in smaller parts. Mostly they snap in half were it is hottest/softest. Usually right by outlet.
I think it ran lean and got over heated.
Carb can be faulty or set wrong. Filters can be plugged, all lot of other stuff as well. Fuel is a big factor in this equation..

There is many "tells" you can see when you take them apart to get a feel of what went south.
When you put it together you see, feel and hear if its right or not.
Performance is the key! If they run right they perform as best.
 
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