Stihl AV 038 chain brake help

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JAKEarbor

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Hi forum, I'm trying to install a new chain brake on a stihl av 038 and I can't work out how to install the band tensioning 'arm' thats hooks onto the spring. Can't find anything clear on the net and don't know how it was originally installed because it came with the whole mechanism missing.
Can anyone tell me what's wrong with the picture?
 
Thank you for the quick responses - they give me a pretty good idea how it should look but the parts are a bit different. I'm beginning to wonder if the new part is compatible with the old - together the guard pivot arm and the arm that comes off the band tensioning arm seem too thick to fit on the post.
 
If you walk into a Stihl repair shop, the number one part that you will see lying around all over the place are chain brake handles and/or saws that need new chain brake handles replaced, waiting to be fixed.. Why is that? :crazy:
 
If you walk into a Stihl repair shop, the number one part that you will see lying around all over the place are chain brake handles and/or saws that need new chain brake handles replaced, waiting to be fixed.. Why is that? :crazy:

I'll take a guess/ The monkey(s) that took it apart cant figure out how to put things back.
 
I'll take a guess/ The monkey(s) that took it apart cant figure out how to put things back.

This monkey's first saw so in this case diagnosis and reassembly has definitely been an adventure... not least because everything from brake to kill switch were missing critical parts. No bits left over on reassembly though which is always a good sign.

Thank you for the diagrams, they're very helpful. Washers and e-clips haven't been installed because of the post issue - the photo from above kind of shows that the spring - band link lever (?) sits out way too far on its post because there's not enough space on the post its arm shares with the handle link lever (?). Every diagram and image I've seen including yours seems to show a thinner handle link lever arm which would leave more space on the post, so I think I need to replace it too. Makes me wonder what was there before though.

And sorry for the inconsistent terminology - learning what things are as I go.
 
This monkey's first saw so in this case diagnosis and reassembly has definitely been an adventure... not least because everything from brake to kill switch were missing critical parts. No bits left over on reassembly though which is always a good sign.

Thank you for the diagrams, they're very helpful. Washers and e-clips haven't been installed because of the post issue - the photo from above kind of shows that the spring - band link lever (?) sits out way too far on its post because there's not enough space on the post its arm shares with the handle link lever (?). Every diagram and image I've seen including yours seems to show a thinner handle link lever arm which would leave more space on the post, so I think I need to replace it too. Makes me wonder what was there before though.

And sorry for the inconsistent terminology - learning what things are as I go.

No offense, was referring to the "repair shop........" comment, post #7.

If working on saw/machine you don't have a manual/IPL for and/or never worked on, take pictures or draw a diagram before taking apart. Then keep parts organized as they come off........I know you started with a basket case.

1) Check that the torsion spring, that goes behind the actuating lever that the handlebar bolts up is installed properly. The short leg must fit into the crankcase and the long leg goes into the lever (see shop manual picture). If the springs legs are not seated that could be the problem.

2) Measure the thickness of the handlebar actuating lever combined with the sealing washer and bell crank at the pivot where it connects. Compare that with the length of the pivot pin from crankcase to it's clip groove. Should be less than pivot pin groove to crankcase.
 
If you walk into a Stihl repair shop, the number one part that you will see lying around all over the place are chain brake handles and/or saws that need new chain brake handles replaced, waiting to be fixed.. Why is that? :crazy:

I hear ya, I recently had to replace 2 brake handles on a pair of ms 290 ,both saws were owned by the same person . One of these saws was missing a chain catcher and threw the chain off and whipped around gouging the gas tank and put a hole in it.

My guess would be either too much Armstrong application to the brake or a limb falling on top of a saw or the saw gets run over .
 
One more thing, your "actuating lever" looks different than shop manual/IPL. Take a close look at the shop manual part

There should be a sealing washer that fits over that, I don't see that either.

If I remember the very early 038 did not have chain brakes. I don't have an old IPL or saw like that. Perhaps that "lever" is just a mount for the early handguard, and wrong "lever" is the problem. Also your part is aluminum, not steel.

Lots of 038 "Frankensaws" out there.

Some/most parts will interchange, some don't. I've got a 038M, two 038S I converted to magnums, some 038 "carcasses" for parts, and a few boxes of parts. I don't think I have any early 038s/parts with the metal tanks and no chain brakes.

Here are correct parts you need, problem solved:

038 brake.png
 
I think all kill switch/throttle assy parts are the same. But if you get used don't try worn out ones. Also make sure they operate choke inside air filter properly.

Some aftermarket air filters/chokes are POS and won't work right. Better a good used then a POS that choke won't work right.

The oil pumps get tired and will pizz out when not running. There are o-rings and a seal that will fix that if rest of pump is sound. Two types of clutch drums(spur/rim) that use different oil pump drive parts. The clutches are real heavy duty and have a bearing that almost never fails, a double needle bearing.

Check your AV mounts and rubber hoses/sealing parts.

The early Tilston carbs (48mm bore 038) were smaller bore. The later Tilstons/038 super were same size as the Bings on the 038M. The Tilstons work fine and are cheaper to get parts for compared to the Bing. I don't see a difference in running the two.

Is your saw a super or magnum, 50mm or 52mm bore?
 
I remember ten years ago when I first started offering to fix chain saws, the first two Stihl saws that showed up had broken chain brake handles. One guy handed me the pieces and said, "I can't figure out for the life of me how this dang mechanism goes back together. It's an impossible mission."
 
I remember ten years ago when I first started offering to fix chain saws, the first two Stihl saws that showed up had broken chain brake handles. One guy handed me the pieces and said, "I can't figure out for the life of me how this dang mechanism goes back together. It's an impossible mission."

How about the new carbs/linkages/gizmos ? Ignitions? New a tool that costs more than a saw to fix it?

About late 80s early 90s saws were last of user friendly, and reliable, of saws I like.

Look under the hood of a new car/truck, want to work on that?


Saws are going the same way.........
 
I remember ten years ago when I first started offering to fix chain saws, the first two Stihl saws that showed up had broken chain brake handles. One guy handed me the pieces and said, "I can't figure out for the life of me how this dang mechanism goes back together. It's an impossible mission."

But then again, some of the new "auto techs', can't put in a set of points in a 68 chevy correctly.

I like my 1940 9N Ford tractor. It has a toolbox the size of a lunchbox. If it breaks down and those tools can't fix things, it's really broken. It's still a 3-brush 6V generator w/+ ground battery. I plow snow all winter and it starts 99% of the time.
 
No offense, was referring to the "repair shop........" comment, post #7.

If working on saw/machine you don't have a manual/IPL for and/or never worked on, take pictures or draw a diagram before taking apart. Then keep parts organized as they come off........I know you started with a basket case.

1) Check that the torsion spring, that goes behind the actuating lever that the handlebar bolts up is installed properly. The short leg must fit into the crankcase and the long leg goes into the lever (see shop manual picture). If the springs legs are not seated that could be the problem.

2) Measure the thickness of the handlebar actuating lever combined with the sealing washer and bell crank at the pivot where it connects. Compare that with the length of the pivot pin from crankcase to it's clip groove. Should be less than pivot pin groove to crankcase.

Haha no worries I gathered as much, no offense was taken.
I will take more photos in future as I disassemble for sure.

1) Got my hopes up and took the spring out to find both both legs are actually the same, so no dice.

2) The handlebar actuating lever and the bell crank are flush with the end of the pivot pin - even with the torsion spring removed and without a sealing washer. Interestingly there's no clip groove in that pivot pin which is odd.

I think you're spot on with the parts I need and could be right about the frankensaw situation so this requires a trip to the stihl shop for the lever and washer.

Kill switch is now working, as is choke, and it seems to run OK though it loses power and bogs down easily so maybe the carby / clutch will need work too. You're right on about the bushes too - several are completely shot so I've got new ones on the way. The air filter is pretty grubby on the outside but I don't know whether it's a problem or not.

I think it's neither super nor magnum - the badge just says 038 AV. Made in west germany.

Thanks again for all the advice too.
 
You should be able to find the parts used or a complete parts saw. There is a lot of 038 saws out there.

The picture I posted of the parts we swiped from ebay. Do a search, seller didn't want too much for the assy.

You can check the bore by removing the muffler and putting a plastic straw in ex port. Turn it over until it crimps the straw. Measure the straw to the crimp. It will be 48, 50, or 52mm.

Is the gas tank metal or plastic? The early saws were metal, but those get swapped out too.
 
Thank you for the quick responses - they give me a pretty good idea how it should look but the parts are a bit different. I'm beginning to wonder if the new part is compatible with the old - together the guard pivot arm and the arm that comes off the band tensioning arm seem too thick to fit on the post.

In your pictures above, you can see the kind of squashed oval shape piece of nylon that the lever the handle hooks to rests against. The nylons slides over a cast part of the clutch side housing. Does anyone know where I can find one? Dealer parts book does not show it and dealer says my serial number does not exist according to their computer. d
 
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