Anyone handy with chainsaws???


91stranger

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I am actually pretty handy when it comes to small engines but this one is baffling me. I have an older stihl 031av with a 20" bar. I got it for $50 and the PO said it runs but is hard to start. I got it home and it actually fired right up for me but ran like crap. Had no torque, bogs when giving it gas and wouldn't stay running. I have so far put a new spark plug in, installed a chip to bypass the points and condenser, replaced the carb and all the gas lines except for the one inside the tank b/c it seems fine, the old gas lines were brittle from not having gas in them. I have fiddled with the high and low and idle adjustments and nothing I do will give it torque to cut through wood. It will run, idle and rev up and sounds like its getting good RPM but as soon as you go to cut a piece of wood it just struggles and can't cut through a 6" piece of wood without baby'ing the damn thing. At first I thought it was the points since that is the common part people say goes bad on these. Bought the chip and it had an old chip already installed. I replaced it anyway and still no luck. Found the carb on ebay for $14 so I put that on and still no luck. Not sure if I need to tear it down and rebuild the complete engine or what. Putting the carb to specs makes it run like crap as well. Any advice on this? I'd really like to use it for bigger trees and save the ms250 for regular bucking. Thanks in advance.

Forgot to mention that I am using 50:1 gas using Stihl synthetic oil. I pulled the muffler and cleaned the spark arrester as well.
 


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Did you do a compression test?
 

8thTon

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Pull the muffler and look at the piston & rings for signs of scoring.

Those chips might not give you the correct timing.

Also, how did you tune it? Properly tuned the H mixture should just clean up when under load in the cut, but when you lift and the rpms pick up you should hear it begin to misfire. Of course if you cannot load it then that has to get fixed first.
 

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Just a shoot in the wind, but does it have a clutch or friction plate. Sounds like something may be slipping.
 

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I remember when I had the muffler off I took a quick glance inside and nothing seemed bad. Everything looked shiny and smooth if I remember correctly. I have not done a compression test yet. I bought a compression tester at a yard sale and misplaced it while re-vamping our garage/house/barn lol. It feels like normal compression when I am starting it though. I would imagine it has a clutch but haven't torn it that far apart. Was hoping someone had some tricks to try. As for tuning it I put all the screws to spec based on the owners manual. It would run with these setting but never could get it to rev up really high like a good chainsaw will. I adjusted the High screw while I had the throttle pegged to try to get it to rev up. I set it as high as it would rev up to for the high screw. The low screw I didn't mess with too much, it wanted to keep the chain turning at factory spec so I turned it until the chain stopped spinning at idle. I set the idle like your supposed to where you turn it back a hair before it dies. Like I said I am normally pretty good with small engines but this one has no balls. Doesn't leak anything when it sits either.
 

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muffler might be clogged.
check the that the choke works.
 

91stranger

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Muffler not clogged. Had it off to clean the spark arrester already. Choke works like it should, carb is brand new.
 

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Does it have a compression release? I had an old saw that the realease stuck halfway and it did more less what you describe.
 

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I set it as high as it would rev up to for the high screw.and the faster
That's too lean, by a fair amount. Even if it runs OK it will burn it up quickly with use. These all-position carbs are crude, and the higher the rpm & airflow the richer the mixture they give. So if you set it for correct mixture at max rpm then at lower rpm it's very lean.
 

91stranger

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Aren't you supposed to set the High screw when giving it full throttle? That's how I always done it in the past. I set it where the rev's sounded the best. And no, it does not have a decompression release. I downloaded the manual and it doesn't mention anything about this issue. Need to find my compression tester...… Damn it sucks having a messy garage.
 

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I set the High screw at wide open but I go to where it sounds smooth, then readjust the Low and idle, then readjust the High side quite a bit richer - you want kind of a "burble" sound with no load, wide open. That way when you've got a load on it, you'll have enough fuel and won't lean out. I do think you need to do a compression test on yours though.

I recently just picked up an 031AV for $20 at a yard sale - the owner said it needed a carb. He had the thing set so that it was basically wide open all the time. Some adjusting later and it's running great.

Definitely NOT my favorite saw by a large margin but it's a Stihl so I guess I'll keep it around. It has the big, heavy, crude feel of the 60's and the cheap plastic of the 70's.

Still miss the 011AVT I sold years ago.
 

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Aren't you supposed to set the High screw when giving it full throttle? That's how I always done it in the past. I set it where the rev's sounded the best. And no, it does not have a decompression release. I downloaded the manual and it doesn't mention anything about this issue. Need to find my compression tester...… Damn it sucks having a messy garage.
No. Initially set it at wide open throttle no load rich enough so it noticeably misfires. Later, tweak it so when in the cut under normal load it cleans up and stops misfiring, but the rich misfire returns when you lift and the revs increase. That is how you know the mixture is correct under normal load.

If you set it clean at wide open throttle no load, it will be way too lean at lower revs under load.
 

91stranger

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^^^That's how I start all my chainsaws but normally have the throttle locked^^^ hahaha j/k. Still no luck even with adjusting it back like you mentioned above. It just has no balls.... Still need to find my compression tester but that's another day. As for now its back to ol' faithful ms250 to tackle my ginormous pile of wood.
 

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^^^That's how I start all my chainsaws but normally have the throttle locked^^^ hahaha j/k. Still no luck even with adjusting it back like you mentioned above. It just has no balls.... Still need to find my compression tester but that's another day. As for now its back to ol' faithful ms250 to tackle my ginormous pile of wood.
Might be a stupid question: your chain brake isn't on, is it?
 


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