Stihl ms311 too much compression.

[singinwoodwackr]

I never found red on a one. They were always grey on clamshell engines.

Red days and Grey days at the factory?

 

[Chevboy0167]

Pick your poison....

 

[HarleyT]

I haven't seen anything but red on the engines for many, many years.

So this guy doesn't use the compression release? Or is it just so worn out that it closes before he can get a good pull on it?

 

[singinwoodwackr]

Have a blown 310 on the bench...we'll see

Not too bad. Will clean up the transfer, order a piston kit and slap it back together. Friend's saw he got for free

 

[rutterbe]

I had that problem after i replaced the jug and piston on a ms 310. I came to find out that i had over tightened the flywheel and caused it to seat further in on the crankshaft thus rubbing on the case. I replaced the flywheel problem solved.

 

[Coralillo Lo Pro]

Would go with maybe Lightning's bearing diagnosis though would definitely look at the starter spool/rope. This has been an issue on a 361, 251, and 250 for me I've recently rebuilt to various degrees, which were maintained poorly and abused badly by others. Assumed hydrolock, but doubtful. Has been as bad after taking plug out and clearing cylinder and putting plug back in. Everything else the same as you describe. The fix for me - at least for now - has been putting a drill and socket on the flywheel nut and turning the engine for a good while. In one case it was also a bad starter cord spool binding up. Most all three saws were impossible to pull til I spun them a bunch with the drill. Then they pulled fine. Many folks go to sheared flywheel keys, timing kickback, or hydrolock, when I think this kind of thing on these Stihls is more often as suggested, bad starter cords/spools or bearings binding up. My experience leans toward bearings, some lubrication from sustained turning the engine over freed the saw up in nearly every case (the 361 is still a bit problematic - may be the starter spool is the remaining sticky point on it).

 

[HarleyT]

I had that problem after i replaced the jug and piston on a ms 310. I came to find out that i had over tightened the flywheel and caused it to seat further in on the crankshaft thus rubbing on the case. I replaced the flywheel problem solved.

Wow!!!

Hard to imagine that!!

 

[stihltech]

I don't get the over tightening the flywheel part. The taper is only going so far. Unless it is cracked or worn, should not happen. Overtightening the flywheel on a saw usually ends up with a snapped crank end.
Something would have to be worn. Or the crank not fully seated in the bearings. That usually ends up not spinning well.

 

[JG33MC]

So I'm fixing up a chainsaw that's been in and out of the shop and someone gave it to me to fix. It's a Stihl ms311. At first the pull chord would nearly bind to a stop and be really hard to turn once every rotation seeming like on the compression stroke. Acting like it was hydro locked. Couldn't even try to crank it you pull as hard as you can and get one turn before it stops, release and same thing, one turn before a hard stop. Pull the pull chord recoil and it spins freely on its own. Pull the spark plug and there's no fluid in the cylinder and the engine spins free with no resistance. I suspected excessive carbon buildup so I pulled the cylinder to see what was going on and the cylinder was perfectly clean with no ridges, the piston had some carbon but nothing that seems like it would cause such high compression to me. I'm going to include pictures of the cylinder and piston. Any help or advice is appreciated.

I posted this same reply yesterday to someone who was having the same issue, but here it is again. Hard to near impossible starting due to too much compression sounds like a fuel issue where fuel is bleeding into the engine when the saw is not being used and this fuel eventually evaporates, leaving the residue oil soaked in the crankcase and when you try to start it again after it’s been stored for a while, that residue oil is picked up by the new fuel entering the crankcase and then pulled into the combustion chamber and settles around the compression rings and on top of the piston and this is why it feels like it has 300 psi when trying to pull start it, because instead of having a 50:1 fuel mix, with each pull of the starter cord, more oil is sucked from the crankcase into the combustion chamber so that it has now become a 5:1 fuel mix making it near impossible to pull the starter cord. The cause of this issue is one of two things. My guess in your situation is that it is a blocked fuel tank vent valve which is causing the fuel tank to build up excess pressure when left unused or it could also be the needle and seat not seating properly anymore and allowing fuel to bleed down in to the engine when not being used. An easy test once you do get it going and burn & blow out all the excess oil (I usually flush them with about a tablespoon of straight petrol by pouring petrol down the spark plug hole, turn it upside down and vigorously pull the starter cord to clear the oil and fuel), is to drain the fuel tank completely and then run the motor and again until the motor complete runs out of fuel that is still in the carb and fuel line. Leave it sit for a few days with the fuel cap loose and then fill it with fuel again and it should fire up without an issue or alternatively store the saw on it’s side with the fuel cap left loose. I would be replacing the fuel tank vent if it now starts easily and runs like it should after doing this test. About a 10 minute job and the part is dirt cheap. Photo attached of my MS310 which may be slightly different to your vent valve setup, but it will be basically the same set up. The later MS311/391 had the vent directly installed into the top of the fuel tank and they are a real pain to replace. Why they decided to make it hard to replace on the newer models, I have no idea as this part (fuel tank vent) is something that regularly fails as the saw gets older and on the MS311/391 the vent is now in a spot where it get absolutely filthy from oil and dust. Cheers