Chainsaw Locked Up - First Use In A While

Pepe_Silvia · November 03, 2019, 07:08:58 PM

My MS660 locked up in the middle of a cut today. Cutting through a ~3' elm log, I was about 75% of the way through. It had been several months since I'd used it. I locked it up and replaced the piston and cylinder couple times when I was learning how to mill with it, but it's been going strong for a few years now.

Seems suspicious that it happened in the first cut after sitting for a while. Any ideas if it might have been related to sitting, should I have done something differently before firing it up, or was it just coincidental timing?

sawguy21 · November 03, 2019, 08:24:40 PM

Fresh mix and what ratio? Did you pull the muffler and take a peek?

Pepe_Silvia · November 03, 2019, 08:53:14 PM

I used the gas that was in it still. I shoot for 40:1. Haven't opened it up at all yet.

ladylake · November 04, 2019, 04:04:34 AM

Most likely running lean from a partially clogged carb, learn how to tune a saw and then you will know when they're lean. Steve

Andyshine77 · November 04, 2019, 02:31:12 PM

Fuel especially pump fuel doesn't last long, looses it's volatility and ethonal fuel absorbs moisture. I doubt anything was clogged that normally will prevent the saw from running at all, bad fuel is likely the cause of the failure. Combine bad fuel, maybe and you see the results.

Greenerpastures · November 04, 2019, 04:11:56 PM

Bad fuel, and it may have also gummed up in the carb,
either will cause your saw to heat up and eventually
lock up.
Given you already had similar issues, you probably know
to take off the muffler and have a look in to see what's going on,
better to do this than starting it up again if it ever frees up enough
to do so.

If your rebuilding it, make sure to do a pressure and vacuum test
to ensure your base gasket and case seals are holding up, no point
in destroying another piston and cylinder through a leak.

And check your carb, strip and clean it, put new seal kit to be safe.

ChrisRoss · November 05, 2019, 01:25:59 AM

Take apart the muffler and clean it. It seems to be a clogged carb issue to me in your chainsaw. The best thing is to use ethonal free gas every time.

Hilltop366 · November 05, 2019, 10:38:43 AM

I've never had saw issues using fuel a few months old or even 6 months old although I try to keep the fuel less than a month, same saw for thirty years.

I will add a question. Does the oil settle out of the gas after awhile?

I do shake the saw (and the gas can if refuelling) before using as a precaution. I really don't know if the gas / oil mixture will settle out but it is a easy precaution to take.

I guess one could put some fresh mix in a clear container and let it set for a while to see what happens.

Bandmill Bandit · November 05, 2019, 11:09:41 AM

Hill Top no worries about the oil settling out of mixed fuel. Not an issue.

How ever the crap that is call gas today has a lot of other separation and deterioration issues.

Do you think your "lockup" is seized piston?

Al_Smith · November 05, 2019, 11:26:41 AM

It could have swallowed something that didn't agree with it's digestive system .It happens .

Pepe_Silvia · November 06, 2019, 09:03:09 PM

Got it apart and one of the circlips had come out. This isn't the first time this has happened. The first time I paid a guy to put a new piston and cylinder and it happened the first time I used it. This time I learned how and put it in myself and it was going strong for a couple years and then did this out of the blue.

Andyshine77 · November 06, 2019, 09:55:17 PM

OEM piston and clip? AM clips tend to do this.

Pepe_Silvia · November 06, 2019, 09:57:29 PM

Aftermarket $40 Chinese job.

ladylake · November 07, 2019, 04:33:41 AM

Yes always use OEM circlips in any 2 stroke engine, most aftermarket ones are too thick a don't fit in the groove good. Steve

Andyshine77 · November 07, 2019, 06:07:19 AM

Even good quility aftermarket pistons from Meteor have subpar clips. Looks like that piston has seen some heat too. OEM and good quility pistons are not expensive so alway go that route.

Al_Smith · November 07, 2019, 06:43:15 AM

See ,you can't always blame the oil .

thecfarm · November 07, 2019, 08:43:22 AM

Ouch!!! :(
I always and I mean always shake the can!! I am very fussy with the oil. During the cold months the oil mix can gets put on the shelf in the OWB. Warm it up. Than I put the oil mix can into the gas can and I let it drain for at least a ½ hour to get every drop. Than off to the gas station for the highest grade of gas I can get. Than I shake the gas can,alot,and put the gas into gallon jugs. Than each time I fill the chainsaw,these gallon jugs gets shook some more. ;D I have no idea if all of the above really matters,as I say,the sun will still rise and the sun will still set. ;D

ManjiSann · November 07, 2019, 08:58:25 AM

OUCH!! I'm sorry this happened to your saw, painful tuition to the school of DIY

What caused that? From what I'm seeing in the pic it looks like a huge groove was gouged into the piston? Is there a matching groove in the cylinder (is that something you can see?) Did the circlip that holds the piston to the rod somehow let loose and gouge through it? ( I read the thread, just trying to understand how the circlip contributed.)

Sorry to ask so many questions :P :P I haven't had to take my saw's engine apart yet but as I plan to keep milling with it I'd imagine sooner or later I'm going to have to and am trying to learn all I can.

Pepe, thanks for posting about this and letting me learn along with you

Brandon

Pepe_Silvia · November 07, 2019, 09:29:49 PM

Quote from: ManjiSann on November 07, 2019, 08:58:25 AM
OUCH!! I'm sorry this happened to your saw, painful tuition to the school of DIY

What caused that? From what I'm seeing in the pic it looks like a huge groove was gouged into the piston? Is there a matching groove in the cylinder (is that something you can see?) Did the circlip that holds the piston to the rod somehow let loose and gouge through it? ( I read the thread, just trying to understand how the circlip contributed.)

Sorry to ask so many questions :P :P I haven't had to take my saw's engine apart yet but as I plan to keep milling with it I'd imagine sooner or later I'm going to have to and am trying to learn all I can.

Pepe, thanks for posting about this and letting me learn along with you

Brandon

Yes, I believe that the circlip got loose and bounced around and eventually ended up in the exhaust port where it got sort of guillotined by the piston. There is a matching gouge in the cylinder. The circlip piece is actually still lodged in there.