Seized up stihl ms290

[windthrown]

Well, I know that the 1127 saws have compensating carbs in them. I also have owned over a dozen of them (290 and 310), and they run just fine with somewhat dirty air filters. The AFs are larger on these 290 55cc saws, as compared to the really small ones on the 50cc 260 saws. From the photo above I do not see a dirty air filter. I see a flocked AF that has some color to it. Yet people on this thread have gone completely overboard on the carb and choked up AF issue, and on various ways that the thing can run lean (in my experience they run rich with either clogged AFs or muffler screens) but that is not the problem with this saw. There was no lean seize or signs of any overheating on this saw and that piston and ring set is down right 'perty. No transfer, no scoring, not even any streaking, which are the typical signs of running lean. So it is far far more likely something else. With the bar code sticker still looking like that on the front of the saw, this saw has really really low hours on it as well. Barely broken in. Likely a factory defect or failed part cause this seize.

 

[maico490]

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.

You ruined your science by using velocity. Velocity is a vector quantity i.e. speed with a direction. As you haven't specified an angular component you are talking about speed. Even then what "speed at the seams" means is beyond me.
As for the rest of the argument my experience is that clogged filters make a saw run rich, compensator or not. Also the flocked filters on the 1127 series don't let enough through to cause a problem in such a short time.
My money is on the piston/cylinder not being lean seized.
One of those unlucky something or others is more likely.

 

[smokey7]

My bet is on the clutch bearing or clutch is jammed up. And the bar groove are jammed up too, causing it to try and turn over the whole stuck package when you are pulling the roap. Take bar off and re try starting it's either that or a screw is stuck in the flywheel.

 

[superw6]

Since nothing was said about chain and clutch we can only assume it wasn't checked. You have just pointed out to me why I usually say nothing to help [emoji52]. Have a nice day


Sent from my iPhone using Tapatalk

 

[VK Johnson]

I've had the snap ring fly off and spit out the clutch bearings before...caught it before it quit, tho...noticed the chain was sagging and took the saw off the line...

 

[smokey7]

Did I upset you? I'm just trying to help some saws jam up when noodling.

 

[BigOakAdot]

Guys, tons of great info thanks to all who replied. I honestly panicked and had to see the piston first. I was dead after a long day of rolling logs around and didn't strip her down. It's my buddy's saw and I'll be heading over to take a closer look. Will keep you all posted. Thanks.

 

[Okie]

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.

 

[Okie]

I had a similar experience with a 028AV awhile back. (about 4-6 months back) Saw had been running and cutting good and when it happened I was doing full bar cuts into a 20 inch green pine log and loading the saw heavy. It just kinda died, pull rope would barely move the engine. This saw has no chain brake.
I took it too work bench, removed both side covers and flywheel turned hard by hand, piston looked ok thru exhaust port, cooling fins clean, breather clean but cowling appeared to be quite warm, but I was not sure of any excess temperature, just appeared hot maybe.
I left MY saw sitting on the workbench and come to computer all depressed and posted issue on here.
replies were saw was run lean pull the piston jug, rip it apart and look at a ruined piston and jug.
I went back to work bench next morning with intentions of pulling the jug and checking piston and cylinder and probably having to go look for replacement saw and the 028 saw was turning over normal. I put it together and it fired up and sounded good. I checked the carb jets and both at 1 1/4 out which was owners manual recommended settings. I took the 028Av and couple other saws to a 20 inch green pine log and used a 3M infrared thermometer (that I reach for quite often for checking bearing, automotive engine temps, HVAC temps etc) and checked the jug temp on the other two saws then when I started cutting with the 028 full bar the jug temp was going to 400 real fast, the other saws peaked at around 360 and was slow getting to the 360 area. I could tell by the loading that the 028 was not overrevving. I adjusted the H jet to 1 3/4 turns (added 1/2 turn out)and when I placed the saw in the full cut under load it momentarily kinda gurgled (4 cycled) then took off and cut good and temp stabilized at around 360 max. The thermometer confirmed the previous overheating and lean condition and was very easy to use aiming the red dot onto the fins of the jug even while the saw was in the cut buried into the log.

I since have bought a Echo pet 304 tachometer mainly because several replies still suspected the saw of overrevving and I was sure it was not because the saw was heavily loaded in the cut and not overspeeding. The pet 304 is a good fast responding digital tach. (about $80 from flea bay)
When I tested the 028 with the tach the max unloaded rpm was 10,200 and in the cut the rpms were around 7200 confirming no overspeeding with the saw set back too 1 1/4 out. Idle is 2200-2260. Rpms were still close to same when H jet out to 1 3/4 and no overheating..
Stihl 028 rpm specs are max of 12,500-13,000.
The saw has cut several loads of firewood since and no problems, runs cuts and idles like new saw.

Appears that the OLD carb had leaned out due to probably aging and the infrared thermometer helped determine real fast the overheating condition.

 

[hotshot]

Okie, WTF is wrong with that tach? Is it set for 4 cycle operation?

 

[Okie]

Good eye hot shot. Had not had enough coffee yet.
I made corrections to the rpms.

Thanks for the heads up.

 

[Full Chisel]

One of my 350s did the same thing once...I thought for sure something had let go and siezed it up. We'll something had let go...it was a loose fastener that had fallen down behind the flywheel and locked it up.

Always check the easy/cheap fixes first! Hope it's nothing catastrophic...

 

[Okie]

link to 028AV seized up issue I mentioned.
http://www.arboristsite.com/communi...hen-later-spins-ok.290338/page-2#post-5767169

I also use only stihl oils and non-ethanol gas in all makes my saws now days.
Found local true value hardware store is a Stihl outlet and prices of Stihl oils within reason.

 

[BigOakAdot]

Hey guys,

Just an update my buddy called me and says "hold on" and next thing I know I hear his 290 revving up. He took a look at it before I made it back over and said the nut that holds the starter rope was over tightened.

Not sure exactly what caused it to kick off abruptly and lock it up but regardless the issue seems to be solved.

Big thanks to everyone on their advice to help figure out the issue. I immediately panicked and assumed the worst case scenario. Pretty standard for me.

-BOA

 

[jr27236]

THAT'S IT!!!! Like a bad ending to a good movie....I'm left going....what????[emoji53]

 

[windthrown]

Actually it is a good ending. My guess would be a starter cog caught and stalled it.

No dirty air filter caused a lean condition leading to overheating leading to a seize with a blown piston, rings and jug requiring a new long block engine replacement problem.

 

[jr27236]

Actually it is a good ending. My guess would be a starter cog caught and stalled it.

No dirty air filter caused a lean condition leading to overheating leading to a seize with a blown piston, rings and jug requiring a new long block engine replacement problem.

Well I guess it is a good ending. I was just expecting to hear worse. But that is a good outcome and thankfully that was it.

 

[HarleyT]

Hey guys,

Just an update my buddy called me and says "hold on" and next thing I know I hear his 290 revving up. He took a look at it before I made it back over and said the nut that holds the starter rope was over tightened.


-BOA

Huh?

 

[maico490]

Glad to hear it's a happy ending.
At least I was right with my diagnosis of an "unlucky something or other"

 

[blsnelling]

I'm not surprised at all. Great news!