I have a love/hate relationship with my ms311. Love it when it works right, hate it when it doesn’t, which is often. It was running great and I was in the middle of a cut on some dead ash and it stopped dead. I couldn’t get it restarted so I let it cool off overnight and tried again. No cough, nothing. I pulled the plug, which looked good and verified visible spark by grounding the plug. Compression seems ok, too. I thought maybe a clogged fuel line, so I pulled the carb and gas poured out of the line from the tank. Any thoughts of what I should look at? Also, I cannot get the chain oiler to work. Last year, I had to replace bearings, rings, and oil pump after the crappy plastic retainer failed in the bearing. I’m on my third aftermarket pump and it doesn’t work consistently. There are no obstructions - all lines and oil passages are clear from the tank to the bar. Not sure I want to continue to throw money at this thing or cut my losses and buy a new saw.
Stilh MS311 Problems
- Thread starter Jims55
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I had one and the coil went bad and the gas line went bad. They wanted a war pension for an OEM coil so I put a Proline $59 coil on it. The gas line is 2 pieces, was a pita to put on and cost $26 OTD at a Stihl dealer ( no AM available that I could find.) I got it in good shape and it found a new home. I will take a MS290/MS310/MS390 over any of the newer POS saws in that line up and any of the rest of them. The AV is a little better on the 311/391, more problem prone, but that is not enough for me to want one.
The newer the Stihl the worse it is, time to change brands. Steve
I tend to agree here. I upgraded a 311 to a 391 and also a 290 up to a 390. The 290/390 outperforms the 311/391 by a nose. Maybe I'm getting better at it, but I have to wonder. Regardless, I saved two saws that were both heading for the landfill.
Bad diaphragm in the carb perhaps?Might try cranking it several times on full choke,if the plug is dry could very well be the diaphragm or the float needle valve stuck. Im not up on newer saws,but this ethanol gas really does a number on carb parts and fuel lines.Good luck with it.
Not that way but tell us exact PSI
Not to overlook the fuel tank vent...Stihl never did settle on the correct way to vent a fuel tank...might not be the problem but never hurts to check.
Had the carb apart and the diaphragm was good as was the needle valve. How do you check the tank vent? Gas ran out of the fuel line when I pulled off the carb so I didn’t think it was a fuel delivery problem. I’ll check compression tomorrow with a gauge and see if it’s in spec. My local Stihl dealer said that if you can suspend it by the starter cord without unspooling it, it should start.
Not sure what kind of tank vent the 311 has but it's usually on top of the tank on the starter side.
Took it to the local Stihl store where I bought it and had it looked at. Only had 60 psi compression which isn’t enough for it to start. The cylinder and piston look good so they’re pretty sure it’s a blown crankcase seal. Time to dissect the saw.
What does a crank seal have to do with cylinder compression? I don't care how good the piston/cylinder "look" there is something wrong. Compression isn't "OK" is it?
If compression is 60 psi with a good piston and cylinder it is either a bad compression tester or compression release on the saw.
My understanding of a two stroke engine is that compression begins in the crankcase. A leak in the crankcase might result in incomplete cylinder charging. Anyhow, I watched a couple of two stroke engine simulations, and this seems plausible. Upon disassembly, it looks like two of the cylinder bolts might have backed off. Looks like I had a leak in the Motoseal between the cylinder and bottom of the crankcase. Going to use loctite on reassembly and pressure check the compression release.
Sometimes common sense thoughts that seem logical just aren't correct.
Read up on two strokes some more and found a really good explanation on why crankcase air leaks don’t impact compression results. Pulled the cylinder and it and the piston are toast. Probably overheated as a result of a crankcase air leak. Doesn’t really make economic sense to fix it. No more Stihls for me.
Just to let you know: any chainsaw can develop a leak..I've worked on saws for years and have found leaks in most brands. I kinda like Stihl saws but I'm no fan of the 311...
How does this make sense? We like to help but misleading information stymes us. Mike
Clean the cylinder up put new oil seals in, a new piston, pressure test and get back to work. I just tore a MS391 down and put new bearings/oil seals in as it sound like and airplane taking off as noisy as the bearing was. It took me about an hour and a half tops as not a bad job, but I have did a lot similar before and they are about like them.
The cylinder has a couple of pretty deep gouges around the intake ports. Maybe I'll save it for a winter project.
Sorry rupedoggy, didn't mean to styme you. What I was able to see of the piston and cylinder with the carb and muffler removed looked ok.
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