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Author Topic: Sthil 038AV carb problems?  (Read 1018 times)

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Offline ReggieT

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Sthil 038AV carb problems?
« on: September 16, 2018, 11:55:57 PM »
Hey Guys,

Just picked up a 038AV...pretty stout runner, yet it takes a few blast of starter fluid before she fires up.
I've never been great outside replacing spark plugs, fuel lines, filters...etc.

Where should I start to get this saw ready for woodcutting and max performance?

Thanks,
Reg

Offline btulloh

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Re: Sthil 038AV carb problems?
« Reply #1 on: September 17, 2018, 12:55:44 AM »
It's not priming.  First thing is to stop using starter fluid or you'll ruin it.  Replace impulse line, rebuild carb.  Probably should go ahead and replace fuel line and filter, air filter.

I have a Stihl from that time zone that still doesn't like to prime unless I hold the throttle.  Since that takes three hands, I just have a little velcro band on the guard that I slide up over the trigger when cold starting. Not a full fix, but everything else has been done and this gets the job done.

Does it start warm ok?  

All the rubber lines and filters probably need attention anyway, so it's a good place to start.

HolmenTree will be along shortly with some better advice, no doubt, but that's the best I can do.   :)
HM126

Offline ReggieT

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Re: Sthil 038AV carb problems?
« Reply #2 on: September 17, 2018, 01:30:14 AM »
Much obliged.
Haven't hit with any starter fluid...that was how the seller was getting it to start.
Just ordered a fleeced air filter, will replace lines, fuel filter, and spark plug also.

Offline Mad Professor

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Re: Sthil 038AV carb problems?
« Reply #3 on: September 17, 2018, 08:19:48 AM »
Most likely choke inside air filter is not closing.

Avoid AM air filters, they can cause this.

Also the shaft runs from on/off/choke switch to choke  lever on air filter can be worn out. I've had 038s where I had to hold my thumb on the switch to get things to choke, PITA.

If it starts cold with a splash of mix, suspect choke first.

You'll get the most gains from just making sure your bar and chain are in proper shape.

Offline ReggieT

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Re: Sthil 038AV carb problems & conversion to Super Status?
« Reply #4 on: September 17, 2018, 07:56:33 PM »
Thanks for the great advice.
BTW...all the articles I see in converting the 038's revolve around the Super to a Magnum.
How much trouble is it to go from a 038AV to a 038 Super?
Or the best method of muff-modding my current 038AV?

Thanks
Reg 

Offline Al_Smith

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Re: Sthil 038AV carb problems?
« Reply #5 on: September 17, 2018, 09:07:41 PM »
Here we go again .If you want a magnum buy one .You'll have more time and frustration trying to center a magnum cylinder over an av base than it's worth .Besides the mag had higher production  numbers than the av or super so they are more readily available .You can enhance an av to pep it up and they do nicely .I've got one and I'd say with what's been done to it it will about keep up with a stock Magnum .
Without getting too involved with how to do it let me say you can do more with the exhaust than anything .

Offline Mad Professor

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Re: Sthil 038AV carb problems & conversion to Super Status?
« Reply #6 on: September 18, 2018, 01:37:22 AM »
Thanks for the great advice.
BTW...all the articles I see in converting the 038's revolve around the Super to a Magnum.
How much trouble is it to go from a 038AV to a 038 Super?
Or the best method of muff-modding my current 038AV?

Thanks
Reg
Al, true there may be more Mags out there, but a Super is almost identical to a Mag besides the cyl mounting holes.  The AVs have a metal tank, smaller carb and some have point ignitions.  You can usually find a dead Super cheaper than a Mag. And AVs for less than that.

Putting a super cylinder on an AV is pretty much a bolt on.  On some you need to grind a bit on the case (mentioned in stihl service manual)  The AV carb is smaller, should put on a Tilly from a  Super or a Bing from a Magnum.

Putting a Magnum cylinder on an AV or Super is also pretty easy.  But more involved than the Super on an AV.

You just slot the Mag cyl screw holes to match the AV/Super case, use a super base gasket for a template. Mark what you need to grind with a sharpie; Ten minutes with a dremel or a chain file.
 
Then you need to open up the access holes through the fins so you can get your t-27 torx at the cylinder screws, which will be tight up against the Mag cylinder when you bolt things up. Again a chain file works fine.
 
Next either chuck the cylinder screws in a drill and turn the heads down a bit with a flat file, or take your dremel and remove a bit from the cylinder above where you slotted the mounting holes.  If you don't, the screws will cant when you try to install them, as the heads will rub on the cylinder, and they will cross thread the case.

The ex port on a Mag cyl is wider than an AV/Super.  Unless you want to do some real porting, just polish up the ex port, then match/grind the muffler inlet to match the port.  
The single port mufflers are not a great place to start with unless you are going to add a port.  The dual port mufflers flow good if you open up the baffle by adding some 5/16" holes, then grind out both outlets as much as you can while still retaining the spark screens.. Stihl also made a triple port muffler, but I've never seen one yet.

The Tilliston Super carb is the same size as the Bing Magnum carb.  I've used both on conversions and they each tune fine.  Note, a  rebuild kit for a Bing is big $$$$.

I've done several of these conversions.  I was given two complete supers in good shape but they had been straight gassed.  The first one I found a NOS OEM Mag P/C assy for, I think I got it for $100.  Then a bit more $ for a gasket/seal set, hoses and carb kit.  That saw is more powerful than my 038M, as everything is new and the muffler flows better.  A new RS chain and drive sprocket and I had <$170 into a like new running saw.

When I did my first one, eleven years ago, I shared what I learned.

Since then others have done these conversions including: more muffler work, porting, and a tight squish. The results were truly impressive.  

Offline ReggieT

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Re: Sthil 038AV carb problems?
« Reply #7 on: September 18, 2018, 02:41:22 AM »
Here we go again .If you want a magnum buy one .You'll have more time and frustration trying to center a magnum cylinder over an av base than it's worth .Besides the mag had higher production  numbers than the av or super so they are more readily available .You can enhance an av to pep it up and they do nicely .I've got one and I'd say with what's been done to it it will about keep up with a stock Magnum .
Without getting too involved with how to do it let me say you can do more with the exhaust than anything .
No here we don't go again.
My inquiry was the conversion of a 038AV to 038 Super status.
I've read the plethora of threads about "Super to Magnum"...  ::)

Offline ReggieT

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Re: Sthil 038AV carb problems & conversion to Super Status?
« Reply #8 on: September 18, 2018, 02:42:50 AM »
Thanks for the great advice.
BTW...all the articles I see in converting the 038's revolve around the Super to a Magnum.
How much trouble is it to go from a 038AV to a 038 Super?
Or the best method of muff-modding my current 038AV?

Thanks
Reg
Al, true there may be more Mags out there, but a Super is almost identical to a Mag besides the cyl mounting holes.  The AVs have a metal tank, smaller carb and some have point ignitions.  You can usually find a dead Super cheaper than a Mag. And AVs for less than that.

Putting a super cylinder on an AV is pretty much a bolt on.  On some you need to grind a bit on the case (mentioned in stihl service manual)  The AV carb is smaller, should put on a Tilly from a  Super or a Bing from a Magnum.

Putting a Magnum cylinder on an AV or Super is also pretty easy.  But more involved than the Super on an AV.

You just slot the Mag cyl screw holes to match the AV/Super case, use a super base gasket for a template. Mark what you need to grind with a sharpie; Ten minutes with a dremel or a chain file.
  
Then you need to open up the access holes through the fins so you can get your t-27 torx at the cylinder screws, which will be tight up against the Mag cylinder when you bolt things up. Again a chain file works fine.
  
Next either chuck the cylinder screws in a drill and turn the heads down a bit with a flat file, or take your dremel and remove a bit from the cylinder above where you slotted the mounting holes.  If you don't, the screws will cant when you try to install them, as the heads will rub on the cylinder, and they will cross thread the case.

The ex port on a Mag cyl is wider than an AV/Super.  Unless you want to do some real porting, just polish up the ex port, then match/grind the muffler inlet to match the port.  
The single port mufflers are not a great place to start with unless you are going to add a port.  The dual port mufflers flow good if you open up the baffle by adding some 5/16" holes, then grind out both outlets as much as you can while still retaining the spark screens.. Stihl also made a triple port muffler, but I've never seen one yet.

The Tilliston Super carb is the same size as the Bing Magnum carb.  I've used both on conversions and they each tune fine.  Note, a  rebuild kit for a Bing is big $$$$.

I've done several of these conversions.  I was given two complete supers in good shape but they had been straight gassed.  The first one I found a NOS OEM Mag P/C assy for, I think I got it for $100.  Then a bit more $ for a gasket/seal set, hoses and carb kit.  That saw is more powerful than my 038M, as everything is new and the muffler flows better.  A new RS chain and drive sprocket and I had <$170 into a like new running saw.

When I did my first one, eleven years ago, I shared what I learned.

Since then others have done these conversions including: more muffler work, porting, and a tight squish. The results were truly impressive.  
Thanks Professor.
BRAVO!!!

Offline Mad Professor

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Re: Sthil 038AV carb problems?
« Reply #9 on: September 18, 2018, 04:28:13 AM »
Reggie, do you have the 038 service manual and IPL? The service manual is too big to post here but the IPL will fit.  If you message me an email address I could send the service manual as an attachment.

The service manual discusses the AV to Super conversion.  When I got the straight gassed 038Ss, I was reading up on the 038 and found that out.  That got me thinking about a Mag cyl.

I decided to try putting on a Mag cylinder on my 038S.  I asked a lot of questions on another forum about trying to do it but as far as I can tell no one had tried it yet, as the bolt pattern is a little larger on the 038M.  You only have to grind about 0.045" slots, but they were not towards the bore center (on a radius) from the existing cyl holes. The easiest solution was to use the 038S base gasket as template. Everything else was just getting the screw heads to fit. There was still enough metal left that there was no issues with air leak from the bore to screw holes.

There are a lot of other saws that will accept cylinders from a different saw with little or no work.  For example 066 cyl will fit a 064 if you tap the case for larger screws, bolt pattern is the same.

If you have more 038 questions just ask. I've been running them for > 20 years.

Offline Al_Smith

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Re: Sthil 038AV carb problems?
« Reply #10 on: September 18, 2018, 04:48:16 AM »
The rebuild kits were very costly at one time for the Bing model 48 when the only place you could find them was a dealer .Things have changed now they are under 10 dollars .
When Oregon started making the basic gasket set less the lever and needle they were around 6 dollars and I bought 5 kits and still have several of them .
I'm not sure exactly when they went to the Bing carb .I have 2 mags,one from Germany and one from Brazil .The later one has a Bing but the German model uses a Tillotson .

Offline Mad Professor

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Re: Sthil 038AV carb problems?
« Reply #11 on: September 18, 2018, 05:07:58 AM »
Good to know about the Bing kits, I'll have to stock up on a couple.

Concerning carbs, I read on another thread that you can keep gaskets and diaphragms from ripping on disassemby by putting thin film of chapstick on them before installing them.

Have not had to pull one apart yet to see how well it works

Offline Al_Smith

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Re: Sthil 038AV carb problems?
« Reply #12 on: September 18, 2018, 05:15:57 AM »
Now then I think the super model must have been a regional thing because I've only seen about 3 of them .You see more mags than any .
The av model uses a hemi domed piston and an offset combustion chamber with a dimpled intake tract .The idea was to lessen the effects of a "short circuit" type of situation of blowing all the fuel out the exhaust port .It probably worked but the design was dropped on the mag because it has a centered chamber and a flat top piston with a smooth intake tract .

The later high impact plastic lower suspension on the mag will interchange with the cast aluminum alloy design of the av .Used this item fetches a lot more than the original part but is more robust against droppage which can break the alloy version .
Like  I said you can make an av run and likely a super also and certainly a Magnum .It just depends on how much you want to do with them .On that subject of "how" I'm not even going to get into to it because there are a dozen ways to skin the same cat so it's more about opinions than anything .Whatever works,works  :)

Offline Mad Professor

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Re: Sthil 038AV carb problems?
« Reply #13 on: September 18, 2018, 11:36:45 AM »
I'll be running 038s until I'm gone, then someone will inherit some good runners.

First one I got was 25 years ago.  A pro logger/forester friend had to "clean out the shed", wifey said so........       I ended up with a 038 carcass, a 038M, a 056M and two 056 carcasses.  His saying was once it dies 3 times it costs me money and goes into the shed.  He had a 028S he wouldn't part with also.

The 056M was complete but had the bad bosch coil, ran until hot.  I did the the coil fix with a capacitor and got a good saw w/parts.

The 038M was filthy.  Recoil jammed with sawdust. Wouldn't run as carb was full of sawdust inside the diaphragm covers.  Looked like a near new OEM piston. Gave it a bath and it ran great. Invested in a new 25" ES bar and RS chain.  No more new parts since except chains, an air filter, AV buffers.  Rubber and carb parts are same.

Also have a couple of my conversions.

There is a 038S -> 038M project I started.  Thought it was a lean seize.  When cleaned up and stripped found out it spit a lower end bearing, not common on these saws.  I've got a few good cranks and a NOS OEM Tecomec P/C assy (back when they were Italian and OEM quality).  That might get the hot rod treatment when I have time.

Offline Al_Smith

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Re: Sthil 038AV carb problems?
« Reply #14 on: September 23, 2018, 06:24:13 AM »
Of all the Stihls made in my opinion the 038 series especially the magnum is the crown jewel of the whole bunch .Some say they are the best hot weather saw ever made .You can still get the parts for them from a dealer ,after market,used whatever .
All it takes is to periodically remove the covers and blow out the sawdust ,no problem .
If you are inclined to hot rod a saw engine they take to modifications very well .If you aren't they still do very well if in good tune .
One thing you have to watch is the top left hand rear  av buffer .If it gets torn,which they will after enough usage it can allow the engine to tilt in an up cut that will tear the intake tube on the bottom where it can't be seen .This will cause a lean run which will in time cook the piston .It's just something most people don't think about but it does happen .

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Re: Sthil 038AV carb problems?
« Reply #15 on: September 23, 2018, 11:02:18 AM »
Yup best to be safe to replace all rubber parts especially when they are 30 years old.
I got a 038 Mag I bought new in 1985 in a box in pieces since about 1986.
Logged with it 5 days a week for a whole year, crank and P/C still in great shape. Broke the fuel tank on it and sat in storage ever since.

Might be one of this winter's projects.
Making a living with a saw since age 16.


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