Frustrated: Stihl ms290 dies after heating up

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A week or so ago, I started a thread about I could not start this used ms290 I bought a year ago. Thanks to help, I did get it started but it kept giving me problems. I finally thought I had it lined out.

(Using new premix fuel that comes in a can.)

Yesterday, found a pin oak tree had fallen over a country road, so, went to get some wood. I could not start it! I decided to drive 30 miles to the Stihl dealer. I told the mechanic that I wondered about the air cleaner because it does not look 'good.' (I didn't know that even a new one has a bit of a dirty look to it.) Anyway, he took the air cleaner off, left it off, and the saw started right up. He looked at my old filter and said it was damp, which is not good. I asked is that fuel or condensation and he said he thought it was condensation. BTW, the store owner, when I was at checkout he came over and said hmmm... that bar is not stock... it's 20" bar. He conferred with the mechanic and clarified that once started, it ran well and all was well with the chain/bar. So, the owner told me that the guy I bought it from had replaced the stock bar/chain with a longer bar that the saw is not designed for, but that at least, he did put the right chain on it and changed the sprocket. He said at least the guy had 'done it right' but that 20" bar is non-stock. He said something along the lines of the saw will work fine just don't push it too hard and just let it cut. I left thinking my problems were over.

Back to the tree, got it started but after cutting maybe 6" deep into a log, it bogged down on me and would not rev up like it was. When I had enough after trying everything I knew, I decided to make the 30 mile drive again. I told the mechanic what was going on and I suspected a fuel problem. So, he decided to cut with it. He made several cuts, making carb adjustments as he went and I thought he was making headway but then it finally would bog down. He decided the carb was likely bad. I asked about putting in a kit and he said they prefer to just replace the carb because it's not much difference in money to me. It was $48 for the carb and $15 install fee. I thought that was okay and off I went thinking I've got it this time because after he installed the new carb, he made cut after cut and it ran like a champ.

I also bought a new chain because he said the chain seemed a bit dull and I thought I needed a spare anyway. I didn't want to wait around until he could sharpen the chain -- I just bought a new one.

I installed the chain. I got back to the tree and finally got it started (again, not easy) and it was revving great. I began to cut and it would not cut! After several attempts, I told my brother that I got the wrong chain! Something is wrong, this sucker won't cut! After a minute or so, it dawned on me... I had it on backwards, lol. I fixed that and it cut like a champ.

After cutting maybe 5 minutes, it went dead. And would not start no matter what I did. I let it cool off maybe 10 minutes and got it going again. Same thing happened. This same routine happened 3 times and I got frustrated and since I had enough wood from these attempts to load the truck, I gave it up. A new air cleaner, a new carb and a new chain and it still won't run right.

I told my other brother about this and he said 'it's your coil.' This was also mentioned by someone on my other thread when I was having trouble getting it started, I think that is when it was. I also read several articles/threads from a google search just now and some people have pointed at potential coil issues. BTW, when I was with the mechanic I mentioned that I had heard it might be a coil issue? He said he didn't think it was because he thought if it was the coil, it wouldn't start back up, it would just be shot. After reading, he might be wrong on that? It could be 'going bad' but not all the way gone?

In reading, people mention vapor lock and some other things. Anyone have an opinion? My $280 saw has now cost me that plus these repairs and it's still not right. Thanks.

P. S. I asked the mechanic about doing a muffler mod / carb adjustment and he said, nope, don't do it unless you want to ruin your saw. I have done a ton of reading on muffler mods and it seems to me, people are doing just fine making these mods to give the saw more power and now that I know I have a larger bar than stock, a muffler mod might be a good idea? (If I ever get this sucker fixed right, I am very frustrated!)

P.S.S. How can I tell what year this saw is? After all of this, I'm thinking I should have just bought a new one!
 
I told my other brother about this and he said 'it's your coil.' This was also mentioned by someone on my other thread when I was having trouble getting it started, I think that is when it was. I also read several articles/threads from a google search just now and some people have pointed at potential coil issues. BTW, when I was with the mechanic I mentioned that I had heard it might be a coil issue? He said he didn't think it was because he thought if it was the coil, it wouldn't start back up, it would just be shot. After reading, he might be wrong on that? It could be 'going bad' but not all the way gone?
Apparently he hasn't had that pleasure yet of an intermittent electronic coil failure yet. I have seen several failure of ignition coils on other 2 cycles and 4 cycle equipment. I don't get many Stihl chainsaws in here most here of the Poulan/Husqvarna line.

Yes they can failed as described. I had one coil of Briggs engine that would only fail once the engine was ran 30 min and sit for 10 min getting heat soaked. I also had Homelite chainsaw where the coil was failing randomly that was literally blowing the air filter completely off due back firing through the carburetor. It did this about half the time.

Another example of intermittent failure w3as one I just got help an Aussie fix. The engine would only slightly backfire through the carburetor after the engine was at full operating temp and that backfiring as very random. I also had Kawasaki mower engine that literally tried to set my pants leg on fire where the ignitor was failing and was igniting the exhaust randomly when a very bang. At first I someone had fired off a 12ga shotgun behind me.

Ignition coils with built-in trigger modules can fail from anywhere from completely to very intermittently.
 
Take off the muffler and look at the piston, look for damage.

Then look closely at the fuel line right below the air filter, you will likely see cracks in it.

And find a new dealer....
 
Take off the muffler and look at the piston, look for damage.

Then look closely at the fuel line right below the air filter, you will likely see cracks in it.

And find a new dealer....

When I wrote the first thread about couldn't get it started after a few months not using it, someone suggested that. I looked at it and it looked pretty pristine to me, although, I can see two very faint lines maybe 1/2" long. After someone showed me what a scored piston looks like (and I saw one at the Stihl dealer yesterday), mine looks nothing like that. When I was with the mechanic, he said "but, did you look at the other side?" I told him no. He said that the other side was what mattered because of some reason, I forget exactly what he said. That's when he took the muffler off of another saw and showed me the horribly scored piston. He said the other side of the piston was fine, and the saw runs good. So, I haven't looked at the other side. The side I can see with muffler removal, I suppose those two faint small lines are okay?
 
The MS290 will run a 20" bar but usually they put one in .325 pitch chain on it. I assume what you have is 3/8 pitch. That will work but I would "go easy" like they suggested. The bar/chain obviously isn't the problem.

As indicated, you could very likely have a coil problem but I think that is less likely than something else. I have worked on a boat load of these saws and while I know coils fail, I've never encountered a bad one on this series.

What Harley indicated about the fuel line is something to look at. Also, many of the aftermarket lines are slightly thicker rubber and they will "pinch off" where the line makes a sharp bend to fit into the recess where the carb pipe goes into it.

This is not a complicated saw and parts are cheap. No matter what is wrong with it, you can get it squared away with help from the site. Where are you located? Maybe there's a member close to there familiar with this saw that can help you sort it out.
 
I would do as Harley say and get a look at the piston yo make sure that is ok and not starting to seize. When it gets hot the saw would die.

My money on the bad coil as AVB suggested. It sounds like a coil that will open up when hot.......they are very hard to diagnose as the saw will run but only till hot. It has the same symptoms as carb/fuel issues. Get a different coil and I sure the problem will be solved.
 
Usually scoring is occurring on the exhaust side of the piston. If it was "straight gassed" it can be scored all around and if it was run with no or a defective air filter, some scoring can occur on the intake (carb) side.

You may want to pull the muffler again to check out the piston again (pull the starter cord slowly to move it up and down so you can see the whole thing). Also, with a flashlight, you can see across to the intake side of the cylinder to see what that looks like. The reason to check this again is that if there is scoring, all the other actions you take will be a waste of time.

A very helpful tool for diagnosing engines of any size is a vacuum/pressure tester. A lot of information can be found with one of these. Mityvac makes a good one. Put it on your Christmas list.
 
All good answers posted already. It's a process of elimination, fuel line is easiest to check, next is pull the muffler and inspect the piston. After that replace the coil with a known good one. If all that still doesn't cure the problem, pressure vac test is in order. Please post back the solution, inquiring minds want to know.
 
Replace the spark plug before looking any further.

Do you really think this could be a spark plug? I asked the mechanic about this (and I obviously don't know much about a chain saw engine) and he said naw, it's firing great. If so, I will not be happy with that mechanic but I will be happy to solve this!
 
Yes, a plug can show heat problems similar to a coil. Try a plug first, they're cheap - and if that isn't the problem then you have a spare plug to add to your tools.
 
First make sure it's not just tuned lean, really screaming under no load. I had one in here tuned by a dealer that must have been turning 15000 RPM + and it did the same thing , ran until it got to hot then died . I tuned it right and it worked good and surprisingly when I pulled the muff it wasn't scored. Sound to me like your dealer might not be very good . Steve
 
I vote tank vent loosen the gas cap after it dies and see if it draws air.

How can I tell if it draws air? Will it hiss or what? I also don't hear very well, lol. I might need to hunker down close to it. Will it be a loud hiss and very brief or last a few seconds? And if this is happening, what would need to be replaced?
 
1 more vote for Harley and middleagemutant.
When it quits, open the fuel cap and close it. If it starts back up, it's the vent.
But the fuel line comes from the tank and makes a 180° bend into the carb. It's probably kinked or cracked
 

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