Showing how to take apart a Stihl ms 391. Showing the oem cylinder. The aftermarket cylinder have to get port timing off it then decide how i'm going to port it.
So mine ran like a beast. 2 pulls and it started. Then I cut 3 trees down and shut it off and it won't start at all. New fuel new filter, new spark plug. Any recommendations on what to look at next? I have spark and it won't even fire at all
Can you tell me a bit about your porting and your pop up piston. I’ve got this saw and no problems so far. Gonna port it and add a couple degrees to the exhaust and intake. I bought a hyway pop up and didn’t really like the look of it. Also ordered a little red barn to look at. In your opinion was the pop up worth it? How did your saw respond to the porting? Mine is always a bit sluggish on throttle response. How many degrees did you change your ports?
I got a duke saw salvage piston for the saw those are really good. I think a popup is worth it on the 391 because it is a clam shell. I put a dukes cylinder on the saw as well but the cylinder could be a hyway cylinder mine is really good port numbers out of the box. I just opened up the lower transfers. If you change port numbers I would try for 102 on the exhaust and try for 75-76 on the intake.
How did you go about getting your port timing numbers? I am just starting the saw work and am hesitant to port without understanding and quantifying the amount I am taking off. Also, how do you feel about plugging the decompression valve? Thanks
If your ms391 is running good and reliable I would not port it. The way those saws are built you can run into velocity issues If not careful porting. One reason why those saws blow up is too small upper transfers so they slow the velocity and run lean on top end for emission. My 391 runs good but does not run well at part throttle only 3/4 to full throttle. You can plug the decomp valve it helps. Would be interesting to hear your stock port numbers.
I just got a Stihl 391 and my choke control won’t allow me to turn the saw off. I have low choke, high choke, run and then when I try to push the lever up to turn the saw off it’s just mush instead of click and the saw keeps running. Do you have any idea of what that could be?
Make sure that linkage is snapped in the choke run lever. Also look at the yellow wire look at the metal S clip is. Make sure that contacts the black wire on the stop position.
I have the same model ms391 and bought it 6 years ago and used it for 3-4 trees and then didn’t use it for 4 years then went to cut a tree at my new home and it ran for about one tank and then after the refill ran for like five minutes and stoped and would start but stop running so I took it to the dealer where I bought it and they took it in had it for 3 months called me and told me it was a blown engine so it would be 650 to repair so I said great repair it and they took another 3 months then I got it back didn’t need it for 6 months started it and it ran through 1 tank and did the same thing ran but wouldn’t stay running so I took it back they had it for 4 months this time but didn’t call me so I called them and they told me the parts were in order I said what parts they said the piston and bearings so I said how long will that take they said they didn’t know so 3 months later they call me and tell me it’s done and then tried to charge me again and I said it’s under warranty from the first repair they said it was user error but I said how can I do what you say happened in one tank they said you use it to hard I said I was cutting branches the size of 3 inches or less hardly hard and so they said fine take it so I took it got home ran it and smelled like plastic and it stopped 5 minutes into using it and the crank locked up!!! Not sure what that is now but I will not ever take it back to that place plus they torqued the cover bolts down so hard I couldn’t get them loose without stripping 2 of them. I had to drill the last one out and use an easy out to get it loose! I have about had it with this but I am thinking heck I’ve got nothing to lose to try and take it apart and possibly repair it myself and with your videos I just might get it running again. Thanks for taking your time to show us the procedure.
Guess I should have watched more of the video. Lol glad she runs well. I have a 028WB (AV Super upgrade), 391, and 661C. I honestly love the 391. I just use it as is. From my research, I found most problems come from two main things. One, people upgrading and losing them to run better. They are not the easiest to mod. Two, novice users not treatment them correct. You basically have to treat it like and old Harley. Don’t dog it, run a wrench over the bolts every so often, and use good non-e fuel. Oooooor upgrade the saw until you do what you did and make it into what it should have been from the factory. I run used to run a 25 on her and it pulled it just fine. 20” runs better. I don’t plan on modifying mine till I burn it up. These videos will help immensely. Thank you!
It was ok but seem to not have the power. So I'm tearing down to see if I can port and epoxy the intake. To get more intake velocity to make the carb work better.
@@kennytheguitarfanatic054 I had a 391 as my big saw years ago. The design isn’t the greatest for making power though anything can be done with enough time, money and effort. I sold it to a guy and scooped up a 441c mtronic professional saw and never looked back. For what it’s worth , I think a guy/gal is better off spending the extra dough and getting the pro version from jump street … Imho ya get more saw and the potential for mods is greater, plus the resale value is much better than the homeowner / farm ranch versions should ya want to sell it
@@fabzacres-blackcat 3yrs ago i got the 391 did not know too much about chainsaws then. Now I know alot more about saws. I got 2 bigger saws now custom built farmertec ms 660 and a 372. I know the 391 is not the best. I have a aftermarket cylinder with good port numbers on the saw. Just seeing what i can do with it for fun.
@@kennytheguitarfanatic054 yah I make my own tools at times especially if they are expensive and are easy to replicate … IF you happen to have the exact size bolt lying around that fits that particular flywheel you can just drill a hole thru the center , and tap it to a 1/4-20 , grind the tip of the thru bolt to a cone and then remove the flywheel - if it’s a different flywheel thread size then you have to make another tool the same way. The eBay tool accommodates a few different STIHL flywheels and is surprisingly robust for the meager cost to your door. For the really frugal a propane torch or heat gun can be used but the puller is sooooooooo much faster. Pull a flywheel in 30sec no problem. By the way I’m not just a mechanic but a journeyman …. Keep feeling the heat 😉
Nice video brother 👍
Can you do a quick video on how to remove the gas tank for replacement? I have a saw with a broken handle and need to replace the whole assembly.
So mine ran like a beast. 2 pulls and it started. Then I cut 3 trees down and shut it off and it won't start at all. New fuel new filter, new spark plug. Any recommendations on what to look at next? I have spark and it won't even fire at all
Pull the muffler and see if the cylinder is scored.
Can you show how to clean the carburetor on the MS391?
My ms 391 blew the transfer port cover off .
Is the bearing snapping a common problem with these
Can you tell me a bit about your porting and your pop up piston. I’ve got this saw and no problems so far. Gonna port it and add a couple degrees to the exhaust and intake. I bought a hyway pop up and didn’t really like the look of it. Also ordered a little red barn to look at. In your opinion was the pop up worth it? How did your saw respond to the porting? Mine is always a bit sluggish on throttle response. How many degrees did you change your ports?
I got a duke saw salvage piston for the saw those are really good. I think a popup is worth it on the 391 because it is a clam shell. I put a dukes cylinder on the saw as well but the cylinder could be a hyway cylinder mine is really good port numbers out of the box. I just opened up the lower transfers. If you change port numbers I would try for 102 on the exhaust and try for 75-76 on the intake.
I can’t get my filter base off the carb I took the two 8mm nuts off and the lever and popped off the mounts still won’t move on the clutch side
The black wire might be holding you. You might have to take the wires were they connect to to coil.
@@kennytheguitarfanatic054 I got it the carb stud must get hot because it was melted to the plate
How did you go about getting your port timing numbers? I am just starting the saw work and am hesitant to port without understanding and quantifying the amount I am taking off. Also, how do you feel about plugging the decompression valve? Thanks
If your ms391 is running good and reliable I would not port it. The way those saws are built you can run into velocity issues If not careful porting. One reason why those saws blow up is too small upper transfers so they slow the velocity and run lean on top end for emission. My 391 runs good but does not run well at part throttle only 3/4 to full throttle. You can plug the decomp valve it helps. Would be interesting to hear your stock port numbers.
I just got a Stihl 391 and my choke control won’t allow me to turn the saw off. I have low choke, high choke, run and then when I try to push the lever up to turn the saw off it’s just mush instead of click and the saw keeps running. Do you have any idea of what that could be?
Make sure that linkage is snapped in the choke run lever. Also look at the yellow wire look at the metal S clip is. Make sure that contacts the black wire on the stop position.
I have the same model ms391 and bought it 6 years ago and used it for 3-4 trees and then didn’t use it for 4 years then went to cut a tree at my new home and it ran for about one tank and then after the refill ran for like five minutes and stoped and would start but stop running so I took it to the dealer where I bought it and they took it in had it for 3 months called me and told me it was a blown engine so it would be 650 to repair so I said great repair it and they took another 3 months then I got it back didn’t need it for 6 months started it and it ran through 1 tank and did the same thing ran but wouldn’t stay running so I took it back they had it for 4 months this time but didn’t call me so I called them and they told me the parts were in order I said what parts they said the piston and bearings so I said how long will that take they said they didn’t know so 3 months later they call me and tell me it’s done and then tried to charge me again and I said it’s under warranty from the first repair they said it was user error but I said how can I do what you say happened in one tank they said you use it to hard I said I was cutting branches the size of 3 inches or less hardly hard and so they said fine take it so I took it got home ran it and smelled like plastic and it stopped 5 minutes into using it and the crank locked up!!! Not sure what that is now but I will not ever take it back to that place plus they torqued the cover bolts down so hard I couldn’t get them loose without stripping 2 of them. I had to drill the last one out and use an easy out to get it loose! I have about had it with this but I am thinking heck I’ve got nothing to lose to try and take it apart and possibly repair it myself and with your videos I just might get it running again. Thanks for taking your time to show us the procedure.
Just lost one crank bearing on the clutch side.
Those oem bearings are not to good. Put a metal caged one in they should last better.
How has she been running?
Guess I should have watched more of the video. Lol glad she runs well.
I have a 028WB (AV Super upgrade), 391, and 661C. I honestly love the 391. I just use it as is. From my research, I found most problems come from two main things. One, people upgrading and losing them to run better. They are not the easiest to mod. Two, novice users not treatment them correct. You basically have to treat it like and old Harley. Don’t dog it, run a wrench over the bolts every so often, and use good non-e fuel. Oooooor upgrade the saw until you do what you did and make it into what it should have been from the factory.
I run used to run a 25 on her and it pulled it just fine. 20” runs better. I don’t plan on modifying mine till I burn it up. These videos will help immensely.
Thank you!
It was ok but seem to not have the power. So I'm tearing down to see if I can port and epoxy the intake. To get more intake velocity to make the carb work better.
@@kennytheguitarfanatic054 I had a 391 as my big saw years ago. The design isn’t the greatest for making power though anything can be done with enough time, money and effort. I sold it to a guy and scooped up a 441c mtronic professional saw and never looked back. For what it’s worth , I think a guy/gal is better off spending the extra dough and getting the pro version from jump street … Imho ya get more saw and the potential for mods is greater, plus the resale value is much better than the homeowner / farm ranch versions should ya want to sell it
@@fabzacres-blackcat 3yrs ago i got the 391 did not know too much about chainsaws then. Now I know alot more about saws. I got 2 bigger saws now custom built farmertec ms 660 and a 372. I know the 391 is not the best. I have a aftermarket cylinder with good port numbers on the saw. Just seeing what i can do with it for fun.
Puller on eBay for 9 bucks … for that price not worth to make your own imho
I had some spare parts laying around it took me about 5- 10 mins to make. Sometimes as a mechanic I go into MacGyver mode to get a job done.
@@kennytheguitarfanatic054 yah I make my own tools at times especially if they are expensive and are easy to replicate … IF you happen to have the exact size bolt lying around that fits that particular flywheel you can just drill a hole thru the center , and tap it to a 1/4-20 , grind the tip of the thru bolt to a cone and then remove the flywheel - if it’s a different flywheel thread size then you have to make another tool the same way. The eBay tool accommodates a few different STIHL flywheels and is surprisingly robust for the meager cost to your door. For the really frugal a propane torch or heat gun can be used but the puller is sooooooooo much faster. Pull a flywheel in 30sec no problem. By the way I’m not just a mechanic but a journeyman …. Keep feeling the heat 😉