Seized up stihl ms290

[BigOakAdot]

Guys,

My buddy just bought a super clean,
Used 290 farm boss off an older gentlemen. We took it to a job today and she seemed to be a great running saw. I've personally never ran a farm saw but sure seemed to be pretty close to my 261.

There was a walnut tree that had a large split right through the middle. Maybe 14" diameter and I was finishing the crack with our 660. Noodles were a little clogged in the kerf so I got the 290 which had a brand new 18" bar and chain on it, to slowly cut through it. At no point had I even buried the bar, and when I pulled the saw up out of the cut she instantly shut off. I had put a minimal load on the saw up to this point. It maybe made ten cuts throughout the day in 14" wood tops.

Didn't sound like a normal shut down and at no point did it bog out like it was out of gas. I instantly knew it was bad. Went to pull the rope and it's locked up.

Next step was to pull the muffler and take a look at the piston. I did minimal research and read it would have scoring if it was a lean seizure. Let it be known the saw was made in 2011 and the gas that was used was the customers fuel. (I didn't think to mention to him to dump the gas and put in his own). Fwiw he filled it fresh from a can when my buddy purchased it.

As you can see piston still has machine markings on it and no scoring. Any thoughts on where to look next. I am completely new to any saw work so don't assume I know how to check into much in terms of breaking it down. I plan on watching some YouTube videos.



I read some other threads where there was an issue with the crank shaft. Any help on where to head next or overall opinions is always appreciated.

Thanks!

BOA

 

[Chainsaw Jim]

It appears that you have an incredibly clogged air filter causing a lean condition to roast the intake side of your piston.

 

[Conquistador3]

Jim has a point: that air filter looks incredibly dirty.
I've learned to clean the filter on my 290 with compressed air every 4 or so hours of work just to avoid making a mess of it. It gets really dirty really soon and it caused the saw to run lean.

Take off the air filter and the carburetor and see if you can take a peak at the piston through the intake port. I am afraid you may not like what you'll find...

 

[mountainlake]

It appears that you have an incredibly clogged air filter causing a lean condition to roast the intake side of your piston.

Explain how a clogged air filter causes a lean condition, should be pig rich like the choke is on. Steve

 

[Chainsaw Jim]

Explain how a clogged air filter causes a lean condition, should be pig rich like the choke is on. Steve

There's a few things going on before the extreme of a full choke affect to shut things down.
It pulls fine particulates which prohibit the lubrication properties of the oil causing overheating to the point of aluminum transfer. The slower air flow aids in the overheating process.

 

[superw6]

Remove bar and chain check clutch and stupid things first


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[BigOakAdot]

Remove bar and chain check clutch and stupid things first
Yeah so could things like that cause the starter rope to not pull at all? Chain moves very freely by hand. Honestly, I've seen some insanely super dirty air filters with the saw running fine. This one had a lil color to it but it looked like the saw was run for less than 24 hours.

Not so convinced on the dirty air filter. Where and how shoul I start?

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[user 122190]

That air filter is dirty, but I wouldn't call it extreme. 290s with the felt material just get ugly fast. Piston looks fine. You've got a break somewhere locking up the saw.

 

[BigOakAdot]

Oh and PS the piston seemed to have plenty of oil. Looked very lubricated to me. And my saw, a 261, was worked way harder with a duller chain. Was pretty darn hot by the end of the job. The 290 did not seem to have excessive heat by any means.


I told my friend to not go the farm saw route. I can beat the **** out of my pro saws and they always run.

 

[BigOakAdot]

It really wasn't that dirty. I just milled with a friend who had an 038 mag packed to the gills with wood particles and he had no issues. I would doubt that's the issue.

 

[Rockjock]

remove the recoil and see if the coil has made contact with the flywheel..

 

[blsnelling]

A lean saw is going to seize on the exhaust side before it does the intake side, and clogged air filter will cause you to run rich, not lean.

It's possible that you lost a wrist pin retaining circlip. However, before I assumed the worst, I'd be looking for something jamming up the flywheel or clutch.

 

[windthrown]

If that AF is dirty, I should have seized up all of my 029, 290, and 310 saws. As said, they tend to run rich when the AF is dirty, and the 290s have compensating carbs. The piston and rings here would be scored silly if it was run lean, was straight gassed, or overheated. None of those things happened on this saw from the look of the piston and rings.

Pull the plug and look at the piston from the top. Check that a torx screw has not fallen into the flywheel and jammed it. Pull the starter cover and check the flywheel/coil. After that? It may be the clutch bearing grenaded. That was common on the 036 saws which had the exact same clutch bearing as the 290. They were updated in the MS360 and in an optional tech bulletin upgrade kit. The stock 036 clutch bearings were prone to blowing out and took out the clutches and/or clutch side bearings. Pull the B&C and pull the clutch drum and look at the clucthes. While you are in there check for crank and bearing play. It could also be that of a long shot thing happened, like a ring broke and locked into a transfer port, the rod snapped, or a piston skirt chipped off and locked up the crank. Or it sucked something into the intake port and locked up the crank.

 

[BigOakAdot]

If that AF is dirty, I should have seized up all of my 029, 290, and 310 saws. As said, they tend to run rich when the AF is dirty, and the 290s have compensating carbs. The piston and rings here would be scored silly if it was run lean, was straight gassed, or overheated. None of those things happened on this saw from the look of the piston and rings.

Pull the plug and look at the piston from the top. Check that a torx screw has not fallen into the flywheel and jammed it. Pull the starter cover and check the flywheel/coil. After that? It may be the clutch bearing grenaded. That was common on the 036 saws which had the exact same clutch bearing as the 290. They were updated in the MS360 and in an optional tech bulletin upgrade kit. The stock 036 clutch bearings were prone to blowing out and took out the clutches and/or clutch side bearings. Pull the B&C and pull the clutch drum and look at the clucthes. While you are in there check for crank and bearing play. It could also be that of a long shot thing happened, like a ring broke and locked into a transfer port, the rod snapped, or a piston skirt chipped off and locked up the crank. Or it sucked something into the intake port and locked up the crank.

Tons of helpful info, thanks. I'm going to strip her down and see what I find. At least this will be a learning experience none the less.

 

[Stihlbillie]

290, 390, and 310 saws don't have compensating carbs.


-chimpboy

 

[blsnelling]

They are compensating Intellicarbs. See item #10.

 

[Chainsaw Jim]

Tons of helpful info, thanks. I'm going to strip her down and see what I find. At least this will be a learning experience none the less.

Thanks for having the patience to sit and sort through some arguing.
Now I feel that I have to get all science minded for a second here to better explain what I meant so people can stop bragging about how dirty they run their filters.
It isn't that filters plug solid, it's that the filtering material is plugged just enough where air starts building velocity at seams which then starts pulling more dust directly into the intake. Generally over time this wears the intake skirt enough to allow the piston to rock and hang a ring. But it can also be extreme enough for melt down and seizure.
I ran three or four tanks of fuel through an ms460 with a brand new piston after forgetting to oil a brand new max flow filter one time. There was fine dust starting to build up throughout the carb and intake and the intake side of the piston was excessively worn from it. I feel that if I had been cutting dry cured wood instead of green then it may have seized up in that amount of time.
It may not cause the saw to run lean, but it can cause lean conditions.

 

[HarleyT]

Nah....

First take the plug out, and see if the thing will turn over.

Then take off the starter, just 4 screws, and look there for problems. See if you can rotate the flywheel either direction. Show us what you find.....

 

[67L36Driver]

remove the recoil and see if the coil has made contact with the flywheel..

+1
And, try to turn it backwards rather than forwards.

Turning it forewords will only make it jam tighter and wreck piston/cylinder. Been there, done that.[emoji37]

 

[Chris-PA]

Based on the picture of the piston/rings, it's hard to imagine it seized, but of course you can only see a portion of it. Still, I'd bet the problem is elsewhere.

Some carb nerd musings:

As to the filter and fuel mixture, I'm wondering if the compensating carb is a good idea on these saw carbs. The all-position carbs are missing a system used in all other fixed jet carbs that keeps the fuel mixture constant as air velocity changes. As a result, the volume of fuel delivered is roughly the square of the air velocity through the venturi - that means when you tune it to some particular rpm under load, as the rpm goes up it will get much richer (4-stroke), and as you load it more and reduce the rpm it will get a bit leaner.

When the air filter clogs it acts like a choke and makes the mixture richer, but it also reduces air velocity through the venturi (which makes the mixture leaner). So these two effects are fighting each other. But when you vent the diaphragm to downstream of the air filter (which is all a compensating carb does), then you remove the first effect, at least until the filter is totally blocked. So now, with a compensating carb (Intellicarb), the mixture will get a bit leaner as the filter clogs. That doesn't sound like a good idea.

Basically, with a real carb venting the diaphragm/fuel bowl downstream of the filter is a good idea as it keeps the mixture constant as the filter clogs. But on a carb that can't hold a mixture anyway, it may do more harm than good.