Stihl MS660 Problems

[Ryan Lee Chambers]

Hey Guys & Gals! New to the site, my son's friend showed me this site last night and most of the night and all this morning I have been checking it out and I absolutely love it! to introduce myself, I just turned 40 a few weeks ago, I have been climbing for around 22 years (started when I graduated and never looked back) and I have owned my own tree service for the past 10 years.

The problem Iam having, I have a Stihl MS660. It was just given to me from the neighbour of a job I was doing yesterday. The owner was an elderly fellow and was truthful in telling me the saw wasn't running and if I would accept the saw as payment to climb up a yellow cedar and raise the canopy of it to allow more clearance over his driveway.. anyways the saw will bark up, and I will have to fight with it to get the RPM's up, once theyre up it seems no matter how much I feather the throttle it just instantly dies. Wont idle for the life of it. I'am thinking it could potentially be a crankcase leak. What is everyones thoughts? The saw is completely stock from what I was told, magnum model, full wrap handle bars, and I always have ran 36" bars, .404, and skip tooth chains.

Greatly Appreciated fella's!!!

Ryan

 

[kr5258]

The first thing I do is a vacuum and pressure test. The vacuum test will show leaks immediately, the pressure test will show where they are.
Could be as simple as a carb rebuild but start with the vac/press test. Pulled muffler will show piston condition.

 

[VinceGU05]

sounds like a lack of fuel ie lean. check filters check impulse line, reset carby screw both L and H in till just lightly snug then 1 full turn out. after that would definitely have to look deeper.

 

[kz1000]

When you say it won't idle do you mean that it keeps reving or does it just starve for fuel and die?

 

[Ryan Lee Chambers]

The saw instantly starves for fuel, then dies. How do I do a pressure and vacuum test? That sounds interesting to do and would love to learn how to do it! Thanks fella's!


Sent from my iPhone using Tapatalk

 

[redfin]

Clean the carb and see what the diaphram looks like.

 

[edaigle]

Hey Guys & Gals! New to the site, my son's friend showed me this site last night and most of the night and all this morning I have been checking it out and I absolutely love it! to introduce myself, I just turned 40 a few weeks ago, I have been climbing for around 22 years (started when I graduated and never looked back) and I have owned my own tree service for the past 10 years.

The problem Iam having, I have a Stihl MS660. It was just given to me from the neighbour of a job I was doing yesterday. The owner was an elderly fellow and was truthful in telling me the saw wasn't running and if I would accept the saw as payment to climb up a yellow cedar and raise the canopy of it to allow more clearance over his driveway.. anyways the saw will bark up, and I will have to fight with it to get the RPM's up, once theyre up it seems no matter how much I feather the throttle it just instantly dies. Wont idle for the life of it. I'am thinking it could potentially be a crankcase leak. What is everyones thoughts? The saw is completely stock from what I was told, magnum model, full wrap handle bars, and I always have ran 36" bars, .404, and skip tooth chains.

Greatly Appreciated fella's!!!

Ryan

Sounds like the impulse line. When I rebuilt mine, I accidently missed to reconnect the line and it was running exactly like you mentioned. Good luck.

 

[Ryan Lee Chambers]

Thanks edaigle! I'll give that a shot in the morning. Still curious about how to do this pressure and vacuum test?

 

[ZeroJunk]

My chain is dull, do I need to do a pressure vacuum test ?

 

[Sprintcar]

Depends, how dull is it?

 

[Ryan Lee Chambers]

Sure I'm new to the site.. But it's not hard to notice a jab being thrown my way...

 

[VinceGU05]

Sure I'm new to the site.. But it's not hard to notice a jab being thrown my way...

I would say no it wasn't !

 

[Moparmyway]

Sure I'm new to the site.. But it's not hard to notice a jab being thrown my way...

Its not intended to poke you, not one bit at all.

There are some on here that might suggest to pressure/vac test a clogged air filter, and that jab was intended for them.

Welcome to AS !

A general look at the essentials might be best before any tearing down.
As suggested, pull the air filter off and pull off the baseplate, its bolted to the carb. Next there should be 2 hoses to the carb. One for fuel, one for a vacuum signal. This vacuum signal is the impulse hose and it is the driving force behind the fuel pump. It will be attached to a fitting that goes to the crankcase on one side, and the carb fuel pump on the other side, so that when the crankcase is under vacuum from the piston moving up towards the spark plug, the fuel pump moves fuel from the tank through the other hose to the carb
Now look at the intake boot, you might need a popsickle stick or blunt object, but move that boot around and see if you see any cracks. Use a flashlight and be meticulous. The boot and hoses should be attached at both ends securely and there shouldn't be any way for outside air to enter. Bend the hoses and the intake boot all around and look with a flashlight. Even a tiny hairline crack is bad.

These are 2 major areas that develop leaks and suck in air, causing lean conditions and erratic operations.Most times, if the operator doesn't recognize the higher idle, prolonged RPM's after throttle release, stalling, etc., it leads to a burned piston and possibly a burned cylinder as well. There are other areas that can develop leaks as well ..... crankshaft seals, cylinder base, muffler bearings, case halves ........ (OK, you got me, that muffler bearing crack was a jab at you).

Best to repair before further damage is done.

I would look at the impulse line first, as that's what my experience has shown as well ............. but a lot of times I find something that doesn't look right in other places. A badly swelled fuel line will show similar characteristics, as will an ethanol damaged diaphragm.

Post up some pictures and we can point your eye to some details that we see which might be of concern if you aren't sure, there is allways someone here willing to help.

If the AS lynch mob shows up, its easy to take to PM's (private message), just click on anyones avatar and click on "start conversation"

Good luck, and lots will be waiting to see what you find

 

[kr5258]

The official procedure is attached. I always do this on saws I receive with an unknown history. Saves time knowing the basic engine integrity and replacing only the bad parts. I use a MityVac 8500 for testing and have various attachments made up for attaching to different saw configurations. Search vac test to get more info on various testing setups that can be used.

Post up a pic of the saw so we can get an idea of condition. Like others have said, may be just a fuel issue.

 

[kr5258]

... I have been climbing for around 22 years and I have owned my own tree service for the past 10 years.

I would think he would be able recognize a clogged air filter...

IF it fails the vac test, switch to pressure and listen carefully to where the air is escaping from. Kids bubble stuff in a spray bottle really helps with the visual identification. Or spend two hours poking around with a popsicle stick and flashlight and still not see the problem.

 

[Moparmyway]

I would think he would be able recognize a clogged air filter...

IF it fails the vac test, switch to pressure and listen carefully to where the air is escaping from. Kids bubble stuff in a spray bottle really helps with the visual identification. Or spend two hours poking around with a popsicle stick and flashlight and still not see the problem.

Guilty conscience, eh ???
Bad experiences with popsicle sticks and flashlights ?
If using a flashlight and a popsicle stick takes you two hours, I can only imaging how long it takes you to pressure test and vac test.
Nobody said that he couldn't recognize a clogged air filter. No need to twist things
A general inspection has proven to show great value in time savings and cost, especially when some commonly known problems can be spotted by a good look around. Its not allways the answer, but it is a start.

 

[kr5258]

You fail to understand that in order to see the the intake boot on the 066/660 you have to remove the carb housing. Vac/Press testing is hands down THE fastest way to identify ANY type of vacuum leak. Be it intake boot, impulse line, comp release, seals, case gasket. Leave the popsicle sticks to the amateurs.

 

[kz1000]

Right on Mopar, is there fuel in the tank, did it set for a long time?????

 

[Moparmyway]

You fail to understand that in order to see the the intake boot on the 066/660 you have to remove the carb housing. Vac/Press testing is hands down THE fastest way to identify ANY type of vacuum leak. Be it intake boot, impulse line, comp release, seals, case gasket. Leave the popsicle sticks to the amateurs.

I have an 066 and I can see the boot with the carb on just fine.
Who said it was a vacuum leak ?
You know for sure there is a vacuum leak ?

His post said;

anyways the saw will bark up, and I will have to fight with it to get the RPM's up, once theyre up it seems no matter how much I feather the throttle it just instantly dies. Wont idle for the life of it.

I think there could be one, but I allways take a few minutes to check the obvious things first. Its got to be a real big vacuum leak to exhibit the conditions he observed


I am happy that you have the ease and ability of press/vac testing, but the OP doesn't.
Like I have said in each of my posts

A general look at the essentials might be best before any tearing down.
There are other areas that can develop leaks as well ..... crankshaft seals, cylinder base, muffler bearings, case halves ........ (OK, you got me, that muffler bearing crack was a jab at you).

A general inspection has proven to show great value in time savings and cost, especially when some commonly known problems can be spotted by a good look around. Its not allways the answer, but it is a start.

............. START by looking, it pays to check the obvious first. Bad gas and water in the carb can cause the carb to make a saw exhibit similar conditions

 

[Ryan Lee Chambers]

A lot of bickering since I was last on here. YES, I know how to tell if the bloody air filter is clogged. 22 years climbing, but also 22 years of wrenching on saws to save money instead of taking them into the shop! Diagnosing a leaky bottom end isn't something I've ever done nor have the tools to do so. Iam going to try every possible fix before I do any pressure/vacuum testing.