Old Stihl chainsaw not running well

[SkunkedAgain]

I've got one of the early 1970s Stihl chainsaws, an 028 AV. It's still generally in great shape. A buddy of mine borrowed it last summer and returned it to me in the fall. Shame on me for not checking, but it was returned with gas/oil mix still in the tank. At that point it would pull start but died when I pulled on the throttle. I drained the gas, gave it a couple of pulls to run the fuel out of the carb, and put it on the shelf for the winter. This spring I put in fresh mix and had trouble even getting it to run. I adjusted the high and low jets back to their initial settings (Low out one full turn and High one and a quarter turn) and turned in the idle screw. Every once in a while it would run long enough for me to start slowly turning out the idle screw, but it dies before I get it to the point where the chain stops turning. I gave it a good cleaning inside and out, checked the air filter, put in a new spark plug, pulled the muffler and cleaned everything, and still am not having luck. It will start but die pretty quickly. Every once in a while it will idle quick until I turn the idle screw out, and die if I squeeze the throttle.

Is there anything else that I can check or try before pulling the carb and replacing the fuel filter in the gas tank? I'm assuming this is a fuel/carb issue. Would it hurt to mix some Seafoam into the gas tank before I go the carburetor clean route? I haven't used that stuff in a long time.

Edited May 2, 2016 by SkunkedAgain

[roony]

I am a Seafoam believer. It's a shade tree mechanics best friend. 

[delcecchi]

When my stihl wouldn't run, I tried everything.  Took it apart, cleaned the carb etc.  Finally went to L&M looking for the carb kit, since there are several different ones.  Turns out it was a cracked fuel line.   They put it in for next to nothing.  Great guys.  This was in Mt Iron. 

The carb is really simple.  You might also check the diaphragm that I think pumps the fuel.  It could be gooped up.  That's  what was the problem on a trimmer that my son had. 

But seriously, taking the carb apart and cleaning it is not hard if you have any ability at all. 

 

[roony]

When I had the cracked fuel line I couldn't even get my saw to start. 

 

[SkunkedAgain]

Thanks guys. I'll check out the fuel line as well. I'm actually driving through Mt. Iron on Thursday so I'll probably pop in with it.

Del - I just did the carb on an old boat motor with plans for another, so I've still got good carb cleaner sitting in a can.

[cylinder]

While you're checking out those other things, check to be sure the exhaust isn't plugged.

[SkunkedAgain]

I soaked the carb for about a week, cleaned it and dried it, blew holes through all of the holes, then put on all of the new gaskets. I replaced the fuel intake and filter, put it all back together, and it still runs rough no matter how I adjust the slow, fast, or idle screws. It still dies when I give it gas.

A guy at the hardware store said that you've got to stick a thin wire through the carb holes. My FIL said that the tork on the carb gaskets can make all of the difference. I'm down to my last few options.

I pulled the stuff off of the exhaust but am not sure how to tell if it's plugged. What should I be looking for?

[leech~~]

Have you done a compression check? The old rings may just be done?

[LoonASea]

NEVER EVER borrow a motorized tool to any one if you want it to run the next time you need to use it ,,,I have been burned too many times to ever do it again ,,,and another FYI  dont sell any gas operated equipment to any one you know unless you have (bunzofsteel) 

[Boar]

Seafoam although works great for the carb it wreaks havoc on plastic fuel lines, special those inside the tank. I have a stihl trimmer that would do the same thing your talking about, turns out the fule line out, started to loose its grip in the diaphragm nipple, it would idle, but under power it would push fuel out of the line on the nipple and die. something to check to.

Seafoam although works great for the carb it wreaks havoc on plastic fuel lines, special those inside the tank. I have a stihl trimmer that would do the same thing your talking about, turns out the fule line out, started to loose its grip in the diaphragm nipple, it would idle, but under power it would push fuel out of the line on the nipple and die. something to check to.

[LindellProStaf]

I had an 032 AV that did something like that.  Turned out that filter thing at the end of the line in the fuel tank was dissolving and there was a crack in that fuel line too.  That was before I started using non-oxy primo fuel.  Little chunks of that filter thing were getting into the fuel line.  

[leech~~]

On 7/15/2016 at 3:53 PM, LoonASea said:

NEVER EVER borrow a motorized tool to any one if you want it to run the next time you need to use it ,,,I have been burned too many times to ever do it again ,,,and another FYI  dont sell any gas operated equipment to any one you know unless you have (bunzofsteel) 

So, asking to borrow your new sled this winter is out?   

[LindellProStaf]

A barber I used to go to always said, "never borrow out your chain saw, your favorite shotgun, or your wife"...........

[LoonASea]

9 hours ago, leech~~ said:

So, asking to borrow your new sled this winter is out?   

YUP!!!!!!!

[Walleyehooker]

I pulled out my saw today to fire it up and it would run and die. At first the primer bulb pumped up but later I noticed it had a crack in it. Next looked at the gas lines and the ones in the tank were detiorating and on the outside were getting hard and brittle which is quite common. So I replaced the bulb and the gas lines and she fired up on the second pull and purrs like a kitten. If you replace gas line get the good yellow color stuff available at most part stores. Also check filer on end of gas line in tank. A lot of times its laying in the bottom of tank like mine was.

[SkunkedAgain]

Thanks for the advice but as you can see above, I did all of that. All new parts.

My buddy who borrowed the chainsaw is very good with motors, and in fact got it running better than I or Twin City Saw was ever able to get it running. Unfortunately, he left the gas in which was a brain fart but doesn't seem to be the issue anyway. And yes, I'd probably loan him my wife if he needed her to cut down the buckthorn instead of the chainsaw!

It's got full compression. Heck, like a wookie it's strong enough to yank your arm out of its socket when trying to pull start. It's nowhere as smooth as my newer Husqvarna.

[Cheers]

so what was wrong with it please tell

[SkunkedAgain]

It's still not running well. That's the problem. Good compression. Carb rebuilt with new parts, blown out and holes cleared. New fuel line. New fuel filter. New air filter. Mixture screws set to spec. I'll probably take it somewhere soon and just pay the money.

[Jim Almquist]

Sounds a lot like my old Stihl. First place rebuilt the carb and it ran good for a day and the next time it ran bad. Took it to L&M in Cloquet and they did a rebuild again. It has ran great for the past 4 years with no problems. They are a Stihl dealer so maybe they use better rebuild kits.....who knows just glad it works when I need it.

[SkunkedAgain]

I gave in and took it to a local Stihl repair shop in town. I'll see what they say.

On the flip side, my newer Husqvarna worked like a champ this past weekend, making quick work of a massive white pine and bunch of skinny birch.

Edited August 3, 2016 by SkunkedAgain

[Surface Tension]

Gas running out the carb.  = Debris stuck in the inlet valve.  No matter what tuning you try and do it won't/can't run right till that is cleared out.

Carb cleaned but still won't run right. = carb isn't clean,  carb isn't adjusted correctly, carb fuel level is off.

If you have the idle set too high, the butterfly is open and your not going to be able to adjust the low speed because the the engine is running off the high speed.  Turn the idle speed down and then adjust the low speed.   Get it to a high idle using the low speed mixture screw. Then turn the idle speed set screw down and then adjust the low speed again.  Again get it to idle high and then turn the mixture out/counter clockwise till the idle speed drops. Leave the low mixture there.  Now go onto adjusting the high speed mixture.

Turn the mixture screw in till you get a good response when you monetarily crack the throttle. Now put a load on it.  A tuned ear will tell you if your lean or rich when the engine bogs or starves for gas. Make small adjustments there. If you bog and notice atomized fuel or smell of raw fuel your rich and you want to lean out the mixture by turning the mixture screw in.  Like the idle speed mixture you want to back out to rich when you hit max RPM.

Carb fuel level is off. That level is determined by the tang hight. That is the lever coming from the other side of your inlet valve. That lever should be level with the floor of the carb body. If the lever it above the carb body you'll be too high/too rich.  If the tang is below the carb body you'll be too lean.  That lever works with the inlet valve and controls the amount of fuel that enters and carb.