Rebuild ms 650 (again) or just buy new saw??

[Pete Moss]

Hi All,

I'm new to this forum, seeking advice re: what to do about my ms 650, which just melted down for the 2nd time in 6 mos...Last November, post Sandy, was crosscutting some Maple when it died. Supposedly reputable Stihl dealer in area said piston was scored, cylinder looked ok, and charged me $300 to rebuild engine (just piston, rings, etc). They said it may have been bad/non-premium gas, blahblahblah, It ran strong for 2 tanks of gas; then, as instructed, I brought it back to them to readjust carb, as they had adjusted it to run slightly rich during break-in of new piston.
I was milling some copper birch on a rather hot NJ day when the same thing happened. Was running premium fuel, E10, with a sharp though not new chain. Took it back to dealer who basically gave me 5 or 6 reasons why it was my fault, including 'marginal' fuel quality (how do they test octane??), abuse of saw, dull chain, alignment of Mercury, etc., all BS. It was out of their warranty period even though I had used it for only 3 tankfuls of gas. I was livid at their unhelpfulness and eagerness to lay the blame. Also told me ms 650 was a POS compared to ms 660 (which may or may not be true).

Anyway, I'm faced with giving the dealer a pile more money (not the same one mind you) to rebuild entire engine, buy parts and try to do myself, or junk it and buy a new 391 or 461.

My question for anyone with experience tearing apart saws is: how difficult would it be for me, with reasonable mechanical skills, to try and rebuild it myself?? This would be the least expensive option, and would acquaint me that much more with the workings of the saw; if it ever happened again I would be less hesitant to repair again. On the minus side, it's like $250 in parts (meaning I will have spent $550 dollars to fix a saw that was around $1100), and unsure if the same freakin' thing won't happen again...

Any and all opinions gladly considered!!_

PS If you want the name of that dealer in NJ will happily forward, though I think they're all made to sign the pledge after drinking the maple flavored Kool-Aid that the customer always is to blame when bad things happen to their impeccable Stihls!

 

[clintonior]

Do it.:msp_thumbsup: Welcome to AS you'll find all the help here you need to put that one back together. Sounds like it was a bit lean when you were milling. You can rebuild it otherwise sorta sounds like a money pit at this point.

 

[Mr.Moose]

Did the dealer do a leak down test on it? Sounds like she might be eating air and causing a lean/hot issue.

 

[nmurph]

It's not hard to tear a saw apart and rebuild.

Post pics of the piston and cylinder.

Milling is hard work on a saw.

I run E10 in all of my saws and have had ZERO problems with it.

You will need to determine what caused the first failure...it is likely the reason for the second one, but that is not true 100% of the time. It could be old fuel, but ethanol will not kill a saw.

 

[bucknfeller]

Welcome to AS.

My guess is that there is an air leak somewhere that the dealer missed, that's what smoked it both times. Plus, you're dealer already burned you once on the "rebuild". $300 for a piston, and rings is awfully steep if you ask me.

Stock rebuilds aren't rocket science, and you've come to the right place to get all the help you'll ever need. But you do need to have some mechanical abilities, and you're going to need to spend a few bucks on a vacuum/pressure testing setup to make sure your saw is tight.

Before I'd take that saw to ANY dealer ever again, I'd send it to a reputable builder from this site. You would end up with a lot more saw for about the same money.

 

[Yukon Stihl]

Hi
If you have any experiance working on engines there are lots of options for you.
There are lots of guys that will help talk you through testing and finding out what really happened.Chances are the saw has a leak somewhere causing a lean condition which fries the piston.
If the cylinder isn't to bad you might just need a piston,rings and gasket/seals.Mabey fuel lines,or intake boot.There are aftermarket parts that will work for you if OEM is too expencive.
Dosn't take to long to test,then teardown to see the carnage.Make sure you test the saw before you tear it down.You will need a vacuum tester and guage,and a way to preasure the saw as well.Lots of threads on the testing procedures on this site.
If you don't decide to fix it then sell it,let me know if it's for sale:hmm3grin2orange:
I don't really know it the 660 is that much better than the 650,but i doubt it.
Good luck
Thomas

 

[nmurph]

Do it.:msp_thumbsup: Welcome to AS you'll find all the help here you need to put that one back together. Sounds like it was a bit lean when you were milling. You can rebuild it otherwise sorta sounds like a money pit at this point.

Did the dealer do a leak down test on it? Sounds like she might be eating air and causing a lean/hot issue.

Based on the info provided, this is pointless speculation without at least a look at the P/C,

 

[Pete Moss]

Do it.:msp_thumbsup: Welcome to AS you'll find all the help here you need to put that one back together. Sounds like it was a bit lean when you were milling. You can rebuild it otherwise sorta sounds like a money pit at this point.

Yes, I was a bit suspicious that it happened just after they readjusted the rich/lean ratio...

Thank you for your encouragement. I think I would have done this without hesitation if I could have found a repair manual or some sort of guidance (eg DIY thread on this site); if this is a good place for my questions then I am off and running!

 

[Whiskers]

Isn't the only difference between the 660 and 650 the top end? Didn't sell well because they were less power and the same weight as a 660, but a few less $'s.

 

[Pete Moss]

Did the dealer do a leak down test on it? Sounds like she might be eating air and causing a lean/hot issue.

I think they checked compression and said it was good after the repair; looking for a compression tester for my own personal use...I am concerned that something maybe off with the carb or timing, but don't really know much about this and wouldn't mess with it without having at least a clue what I'm doing...

 

[Whiskers]

Did they ever tell you what they thought caused the first failure? Did they pressure test your saw?

 

[bucknfeller]

I think they checked compression and said it was good after the repair; looking for a compression tester for my own personal use...I am concerned that something maybe off with the carb or timing, but don't really know much about this and wouldn't mess with it without having at least a clue what I'm doing...

Compression test, and leakdown test are two different things. A compression tester is nice to have, but you can't find an air leak with it. You need to do a vacuum test on that saw.

 

[Pete Moss]

Hi
If you have any experiance working on engines there are lots of options for you.
There are lots of guys that will help talk you through testing and finding out what really happened.Chances are the saw has a leak somewhere causing a lean condition which fries the piston.
If the cylinder isn't to bad you might just need a piston,rings and gasket/seals.Mabey fuel lines,or intake boot.There are aftermarket parts that will work for you if OEM is too expencive.
Dosn't take to long to test,then teardown to see the carnage.Make sure you test the saw before you tear it down.You will need a vacuum tester and guage,and a way to preasure the saw as well.Lots of threads on the testing procedures on this site.
If you don't decide to fix it then sell it,let me know if it's for sale:hmm3grin2orange:
I don't really know it the 660 is that much better than the 650,but i doubt it.
Good luck
Thomas

Hi Yukon,
Is a vacuum tester the same as a compression tester? I thought I saw one for about $30 on the web. Sounds like a good tool to have. I will certainly let you know if I decide to sell it/will post on this site first if that's what I decide...

 

[Pete Moss]

Isn't the only difference between the 660 and 650 the top end? Didn't sell well because they were less power and the same weight as a 660, but a few less $'s.

I think that's correct. Evidently market wasn't good for the 650 so they discontinued it. Kind of a silly idea, and had I known at the time would have gone for the 660...

 

[Whiskers]

No, a compression tester and a vacuum tester are completely different things. A compression test is done to verify the rings are sealing well enough against the jug. A vacuum and pressure test put positive or negative pressure on the crankcase to find air leaks.

 

[bucknfeller]

Click it, and read up a little bit...


http://www.arboristsite.com/chainsaw/42768.htm

 

[Pete Moss]

Compression test, and leakdown test are two different things. A compression tester is nice to have, but you can't find an air leak with it. You need to do a vacuum test on that saw.

Oh OK, gotcha. Two different tests. Again, I think they said there 'were no leaks', so maybe they did vacuum test it...

 

[watsonr]

No, a compression tester and a vacuum tester are completely different things. A compression test is done to verify the rings are sealing well enough against the jug. A vacuum and pressure test put positive or negative pressure on the crankcase to find air leaks.

And you should do it BEFORE tearing it down, then when you have it apart, fix the issue once and for all.

 

[struggle]

Just a couple of thoughts.

1. At all cost avoid using any E10 fuel.

2. You said milling and if you are doing so with the exhaust still restricted as it came from the factory I would be willing to guess the saw overheated in the process of milling due to the restricted exhaust cuasing a stock saw to wrok really hard for what you are doing asking of it.

I run a ported MS660 for milling and it earns every baord foot it makes milling. Nothing easy about milling. I can't imagine doing it with a stock saw.

3. As stated saw needs to be pressure/vacuum checked to rule out air leaks (not the same as compression testing)

 

[nmurph]

1. At all cost avoid using any E10 fuel.)

I use E10 exclusively and it isn't the boogeyman it's made out to be.

2. You said milling and if you are doing so with the exhaust still restricted as it came from the factory I would be willing to guess the saw overheated in the process of milling due to the restricted exhaust cuasing a stock saw to wrok really hard for what you are doing asking of it.)

Yes, long cuts at high RPM, with the added dust.

3. As stated saw needs to be pressure/vacuum checked to rule out air leaks (not the same as compression testing)

It should have been done by the dealer the first time, but many don't know how or want to take the time to do so.


The first failure could have been caused by several factors. The second time could have been caused by those factors with the added cause of inadequate clean up of the cylinder in the first failure.

I want to see the piston and cylinder...it will likely tell the story.