1976 Stihl 020AV restoration project

Glad to read you got it started looks like it's going to be a really worth while project.

 

Screen is clean.

I replaced the starter cord, and have been able to get the saw to run at wide open throttle for 4 to 5 seconds at a time and then it dies. Motor sounds good.

I guess I still need to play around with the two jets to get it to idle and run right...

Slow progress... I'm OK with that.

 

Ok...
Question from a guy who is not a mechanic. Had no one to teach me and wasn’t interested as a kid or young man, like I am now that I’m older. I’ve never been afraid of tearing into things, just never had any guidance.

Once a saw is cleaned up like this and put back together and it’s firing/running, how do you go about adjusting the jets to get the thing to idle and stay running? Is it something you just have to mess around with adjusting it, or is there a proper starting point?

I understand you don’t want it too lean on the high end when under load at full throttle, just backed off a smidge. I have heard that keeps the bearings from over heating. Sounds like good advice.

 

There are initial carb settings for a starting point and you fine tune from there. I think most are available on the internet. Some use 1.5 turns out from closed as a general rule.

 

Hardest part for me, after a full tare down and clean of the carb, is getting the idle set. Like Chud says, 1 to 1.5 on H and L are norms from my experience. And I set them there and leave them for the most part until I can get it to run for at least a little bit. Then it’s a dance of diminishing failures between the L and the idle. There’s some good YouTube out there on how to dial in the low once you close on the idle.
From the L and idle, now I look at the H. I use a tach. I look at the exhaust. And I feel how it it transfers from hardly any throttle to WOT.
And then tweak when good with that.

 

I watch Buckin’ on YouTube some and he has a couple guys that work on his saws. Haven’t seen him do much with idle because most of his saws are already set for idle pretty good.

I have seen where he has dialed the high side back just a bit because under load the saw will start to just barely cut out from being too lean. I guess from being set to max rpm. A lot of times he’ll here the rpm’s cut out ever so slightly so he’ll stop and back it off just a small 1/4 turn or less and put it back into the wood under load and when he gets it to stop cutting out he’s done. I had to listen to it several times before I could even hear it. So I suppose in his case setting rpm’s by a tach is good, but he sets the H jet where the saw likes it to be set, where it runs without cutting out. I believe he has stated that is usually just shy of max rpm’s. At least that is what I understood him to say.

For idle 1 to 1.5 turns from closed. Ok. I had never heard that before. Good to know, tweak from there. Thanks for the explanation.

I know of some of the mechanics Buckin’ mentions, but I haven’t watched any of those guys videos. I probably should just for my own knowledge. The Tin Man is one guy who works in saws for him, another is Donnie Walker, and maybe a couple others. I personally don’t know any good mechanics besides my dad, but small engines isn’t his specialty and local folks at shops haven’t helped me much in the past.

 

A full tear down is not something I would do because I don’t have the tools and it’s not my wheel house. If I had the tools, then I might, but at this stage of my life it isn’t likely to happen. Watching someone do it on o have a better understanding of it is more likely. Doesn’t take much time to turn a screwdriver and make adjustments though and then gain the knowledge as to why the adjustments are needed.

Sorry for taking the thread off the rails.

 

Cool thread! I also have the first saw our family ever had. My dad and I went halfies on it. Ancient history I tell ya!
I want to caution anyone learning to set idle about the chain being very likely to turn during the process. Certain amount of danger lurking there. Be careful!

 

I have heard that if idle is right, then the chain should not turn. I have no idea if that is right or not. I would assume chain tightness would have effect on that statement.

 

True. I meant in the process of getting there. I find it easier to bracket the low jet if the idle is in a higher place. (not as likely to stall out). Once you are close with the low tune, the idle speed screw is set and no chain movement is to be tolerated.

 

Howdy All.

Heres an update...
I got the carb put in and put the two halves of the saw back together, added some fuel and started pulling...

After about 10 pulls, the saw will run wide open with the trottle at rest, and then stop.
It will take about 20 pulls again to get it to repeat this, and again, it only runs as if it were wide open.

Ive tried almost every H and L jet setting combintion.
Is this the dreaded "Run Away" syndrome due to running lean?

I think I could either have a leak at the carb boot, or as Scotty Overkill said, the Crank Shaft seals are letting air in.

Any suggestions?

 

Definitely sounds lean

All the soft goods are suspect on that saw if it hasn’t had a deep fix. Any saw that age really. A couple ways to go from where your at now. Pressure and Vac test to find the offender, which is about as much effort as prep to replace all the soft goods, or replace the rest of the soft stuff.
If you haven’t replaced the impulse line, that’s the easiest first place. And sounds like a likely spot.

Another spot to review is the metering valve lever in the carb. Make sure that’s not set too low. And check the gaskets under the plates. That carb doesn’t have Welch plugs and relies on a plate over specific diaphragms, and the kit comes with different varieties and not all will line up with the ports.

 

Well, I split the case on the saw again looking for the elusive impulse line. There is only one hose that goes to the top of the carb right above the fuel line from the fuel tank, and it is in very good shape.

So I then took the carb boot off and found a small opening at the lower right hand side. The rubber around this hole has some roughness and the rubber is kind of stiff, so this may be a potential vacuum leak. (I'm not sure what that opening is for.)



So I guess the next step is a new carb boot...

Eventually I'll get this thing running.
Thanks for all the input everyone.

 

That hole is the impulse...

 

Thank you for confirming that.
I've got a new one on order. Let's see if that helps solve the problem.
(Fingers crossed )

 

If the new intake doesn’t work, verify linkages and then suspect the carb. A racing saw upon startup is almost always a carb issue if the fuel line/filter, etc. are new. Most seal leaks cause wonkey or super inconsistent idles. Many can be tuned out (temporarily) unless the seal/bearing is really bad. You may have to back out the L and LA screws significantly more than factory. At that point, you can spray WD-40 or brake cleaner near the seals, cylinder area, even intake (avoid air filter). If the saw loads up and dies quickly, you have an air leak at that point. If not, then it’s a carb problem. Adjust the metering lever, make sure your gaskets are correct, and carefully clean all passages with carb cleaner. Look through the needle passage while holding it up- you should see light coming in.
I back out the H and L screws for carb cleans. I see you did the same… good! Dont get cleaner on the new diaphragm or gaskets.

Shops around here are almost done dealing with two smoker carbs. Many won’t work on anything except Stihl and pro-level Husqvarna. Patience is key. There’s only a few spots in saws that can leak air. Eliminate those and it’s nearly always a carb problem.

 

You don't need specialty tools to do some basic work on the saw. The only thing I had to buy was the Stihl piston stop tool and some carb cleaner spray. Otherwise a flat head, a torx bit (T25 or T30 I can't remember), some rags, a 19mm socket for the clutch removal......8mm socket for the carb nuts (at least on my 028 and 034).

"...this stage of my life...."

It's never too late to learn my friend....unless you're physically unable to do something....Watch some videos on YT and read a lot of forum posts. You'll have to do your homework and do a bit of filtering out of bad advice.....but I was able to bring an 028 back to life having never worked on a saw before in my life with the aforementioned tools (didn't need the piston stop on the 028 but I need it now on the 034).

The idle adjustment is literally pulling the trigger of the saw.....if you turn it up too high the chain will move......so basically what you want is to adjust it just right - to give it enough gas to not stall out......but not enough to move the chain......

If you try your hand at it, you may fail. But if you don't try at all, you've already failed.

 

I just meant at this stage of my life I wouldn’t likely invest in specialty tools for small engine or automotive repairs. I already do basic stuff.

 

I do agree though, it’s never too late to learn.

 

Well here's the latest update. I give up.

I've had this thing apart more times than I can count now. I've tightened every fitting, tried every possible carb adjustment combination and the darned thing just won't run.

It making me more frustrated than it's worth. It's going on the back of a shelf somewhere where I don't have to look at it anymore.
(grumbles incoherently to himself and wanders off into the darkness. ) [ end scene ]