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Stihl 038 mag problem

Started by Alta1274, November 02, 2013, 12:51:14 AM

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Alta1274

RE: Stihl 038 Mag
Have not used the saw in a couple of years and I am having a frustrating issue.  The saw aside from this issue runs perfectly.When starting a cold saw, far to often the saw will misfire and rip the starting handle right out of my hand, Very painful to fingers. Seems like it is firing before the piston reaches TDC. Once this happens it is as if the saw  is now on steroids and has super compression. You really have a hard time pulling the cord. If you let is sit for a minute or so the compression bleeds down and you can pull it normally. Checked to make sure the key was not sheared and found it just fine; checked the flywheel/magneto gap was  pat .010" and the plug gap at .020" However, put in a new plug.  BTW, free wheels beautifully with plug out. Piston head looks clean . Exhaust muffler is clear/clean. Anyone have any suggestions? It has always needed a forceful pull but I do not recall this issue.
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

Saw Dr.

Your carb inlet needle may be slightly leaking, causing a hydraulic lock condition.  Do you need to use the choke to start the saw when cold?  Is this saw an electronic ignition?  I know all Mags came that way, but not sure if yours is a conversion.  If it has points, they could easily be the issue.  You could also try another coil.  That -1300 coil is very common.
I don't try to explain to others why I play with chainsaws.  For those who already know, no explanation is needed.  For those who do not, no explanation is POSSIBLE!

Super 250

lone wolf

Check flywheel to coil air gap use a new spark plug clean the carb out and tune properly. It almost sounds like you aren't getting enough gas in at first.
7900                                                               461
046
440
261
200T

thecfarm

Alta1274,welcome to the forum.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Alta1274

My error for not being clear on the type of ignition. This saw is a commercial version (white grip) and has an electronic ignition. (i.e. three laminated pole positions on pickup). There are no points. The air gap to the flywheel is on spec as is the new plug gap. I don't think saw is flooding. I do need to use the choke until there is a sputter, then choke is off with the throttle locked in the starting position.   Wouldn't  I smell fuel if the needle is leaking (i.e. causing a flooding condition on start)? It does seem as if this is a pre-firing issue.  However, this does not occur  before it is choked . How would I verify that there is a needle leak other than looking down the carb throat? I consulted the local Stihl dealer and he did say this model is an aggressive start.   OK, but it should not be to the point that it (pre-fires? and rips the cord out of your hand.  (Note: No loud backfire heard) Other than this issue this saw is a  real strong performer with a 20" Sorry for being so wordy but wanted to give as accurate account as I can.
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

Duane(Pa)

Quote from: lone wolf on November 02, 2013, 09:16:18 AM
Check flywheel to coil air gap use a new spark plug clean the carb out and tune properly. It almost sounds like you aren't getting enough gas in at first.


OMG?

ZeroJunk

It is not unusual for those vintage saws to kick back if you don't pull it hard enough to get it over. Flat top 066's and 064's are terrible and will take the meat off your fingers if you get a little lazy pulling the cord. Sometimes you just have to scream bonsai and go with it. Keep in mind that it is timed to fire quite a bit before top dead center and if you don't pull it hard enough to get past that it will go the other way.

Saw Dr.

Quote from: ZeroJunk on November 02, 2013, 11:54:37 AM
It is not unusual for those vintage saws to kick back if you don't pull it hard enough to get it over. Flat top 066's and 064's are terrible and will take the meat off your fingers if you get a little lazy pulling the cord. Sometimes you just have to scream bonsai and go with it. Keep in mind that it is timed to fire quite a bit before top dead center and if you don't pull it hard enough to get past that it will go the other way.

Yup.  You may want to install a D type starter on it if you are still fighting it.  An Elasto-Start grip would also help the finger ripping issue.
I don't try to explain to others why I play with chainsaws.  For those who already know, no explanation is needed.  For those who do not, no explanation is POSSIBLE!

Super 250

Fatcougar

Sometimes you just have to scream bonsai and go with it

   Haaahaaa, made me laugh! Too funny.  :D
Fatcougar
Stihl 461-R
Stihl 026
New Holland TC30
Rankin 3 point Splitter

lone wolf

Pull it real slow a few times to prime it then let it fly with all you got. I dont think from what you say it is flooding or it would drip out exhaust try to richen the L up a 16 of a turn and try again. It sounds  like it is lean to me.
7900                                                               461
046
440
261
200T

WidowMaker

Nuther AS refugee here. Seems like a nice place. I don't post a lot, lurk a bunch.
To the OP how did you get hold of my saw...I have the same saw with the Exact same issues. I am considering retarding the timing a bit to see if that won't help.
This double DanG thing will/has hurt me...

HolmenTree

You tender foots have to toughen up a little :D
My 038 Mag and 066 red lite have the same personality,  back in the day that was expected from these saws.
The only saw I own that I "need" to use a decomp is on my 090 AV.
Making a living with a saw since age 16.

Alta1274

Willard,
What can I say, you are the 038 expert.  Guess I am just a tender fingers albeit a 70 year old one. I'll just have to toughen up! Bonsai!!
Bob 
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

Saw Dr.

Quote from: Alta1274 on November 02, 2013, 11:28:39 PM
Willard,
What can I say, you are the 038 expert.  Guess I am just a tender fingers albeit a 70 year old one. I'll just have to toughen up! Bonsai!!
Bob

For $20, the Elasto-Start grip is larger and will be a bit easier on the hand.  The 056 Mag is the same way.  You had better have your big-boy pants on when pulling that one over.
I don't try to explain to others why I play with chainsaws.  For those who already know, no explanation is needed.  For those who do not, no explanation is POSSIBLE!

Super 250

Alta1274

I want to thank you all for your good suggestions and tips. Perhaps the Elasto grip is the way to go. I do have some arthritis in my hands. I have looked on eBay and it seems that they are all sold out of Great Britain. Do you know of any American suppliers?
Thanks again to all of you.  :) :)
Bob 
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

WidowMaker

Quote from: HolmenTree on November 02, 2013, 05:49:04 PM
You tender foots have to toughen up a little :D
My 038 Mag and 066 red lite have the same personality,  back in the day that was expected from these saws.
The only saw I own that I "need" to use a decomp is on my 090 AV.


====


I think its a little more then that, I have an 056AV, 056 Mag, 056 MagII and a 064 Mag, and granted they can bite you if you limp wrist them. This 038 Mag
is worst then that, it don just bite, it tries to eat you up, may haps a decomp valve is the answer...
Bye the way I am 69 yrs young myself...

joe_indi

This misfire or kick-back happens if your crank needle bearing(s) are worn out.
When this happens it creates a play between the piston and the crank.
The crankshaft turns over as usual but the piston moves up a bit later than normal
So the fuel mixture ignites a bit before it should, unless you are pulling the starter fast enough.
The solution? Mark the current position of the ignition coil, remove it and file the holes so that you can move the coil about .5 to 1mm in the direction that the flywheel turns. This will retard the ignition timing in relation to the current condition of your crankshaft.

celliott

Quote from: Alta1274 on November 03, 2013, 10:31:01 AM
I want to thank you all for your good suggestions and tips. Perhaps the Elasto grip is the way to go. I do have some arthritis in my hands. I have looked on eBay and it seems that they are all sold out of Great Britain. Do you know of any American suppliers?
Thanks again to all of you.  :) :)
Bob

Go to your nearest stihl dealer and order a ms460\461 rescue saw D handle grip.
Chris Elliott

Clark 666C cable skidder
Husqvarna and Jonsered pro saws
265rx clearing saw
Professional maple tubing installer and maple sugaring worker, part time logger

Alta1274

Joe,
All the way from India! Wow! World coverage, amazing! I will pull the plug and recoil starter to get to the flywheel and see if there is any play in the piston and crank relationship. This is something that never occurred to me but a now obvious potential issue. Should be easy to check out. Is this a common issue? If I am correct, I think the  ignition setting is supposed to be 2.4 to 2.8mm before TDC @ 8K RPM.
Definitely something to consider though!! I will let you know what I find, because as you can see there are others with the same issue.

Re: The pull handle suggestion ,Thanks  Chris

Thanks to all,
Bob :) :)
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

malce

Mine does exactly the same, let us know if your timing does need to be altered.

WidowMaker

Quote from: joe_indi on November 03, 2013, 11:34:12 AM
This misfire or kick-back happens if your crank needle bearing(s) are worn out.
When this happens it creates a play between the piston and the crank.
The crankshaft turns over as usual but the piston moves up a bit later than normal
So the fuel mixture ignites a bit before it should, unless you are pulling the starter fast enough.
The solution? Mark the current position of the ignition coil, remove it and file the holes so that you can move the coil about .5 to 1mm in the direction that the flywheel turns. This will retard the ignition timing in relation to the current condition of your crankshaft.


====

I would think that if the crank bearings were that far gone one would have more the kick back problems.

This saw has been like this for the 10+ yrs I've been assocated with it, and it gets used every years to cut 10 to 12 cords of firewood...not a shelf queen...

Al_Smith

I don't think the 038 mag ever had points ignition.Some of the very early 038 av's did though .

They can be prone to kick back .Now do as you like but pulling them over slowly is a sure way to  kicked back .Ask good ole  Fred AKA Stihl Boy what happened when he checked the compression on mine with the mag hot once .Nearly defingered him D-Handle or not .

Pull that thing over like you mean it .BTW this model is my favorite of any Stihl ever made .It isn't all that old either .As far as I know they still make either the 380 or 381 abroad ,no longer available to the North American market .

Alta1274

Well Guys,
As promised I have done a little experimenting, and I found that when blocking the piston travel at "bottom dead center" by firmly holding a calibrated wooden dowel on top of it, I can obtain some lash as measured on the flywheel perimeter at the ignition pickup of 5.25mm without any noticeable movement to the dowel/piston by very gently moving the flywheel back and forth. This would seem to mean that there would be a delay at top dead center for the piston in relation to the plug firing of half of that or 2.63mm. If you add that to the OEM spec for the fixed spark advance of 2.6 mm you would have ignition 5.23mm before the piston reaches TDC. The Stihl manual indicates a tolerance of 2.4mm to 2.8mm at 800RPM. I do not know what the timing should be at zero RPM, but there is definitely some lash in the (crank to piston) system which could account for the  vicious kickback I am getting on attempted starting. I guess it is either rebuild or big boy pants with a bonsai attitude or do a retard filing job on the ignition module holes. In any event I am going to get the suggested "elastostart" handle system. At my age, felling and bucking firewood should be enjoyable not painful. Thanks again for all your helpful and amusing comments.
Bob :) :)
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

WidowMaker

I think what your measuring is  dwell time at TDC and BDC. That period of time that the pistion is stopped prior to reversing direction. There is a slight amount
fo crank move movement with out the piston moving at the top and the bottom of the stroke.

Al_Smith

Angular measurement at bottom and top dead center can vary as much as 8 to 10 of angular movement before you can detect a movement of the piston .This is simpley a matter of geometry because of the relationship of the crankshaft throw.At 90 degrees movement and angular measurements are more liniar .

For example to properly set a degree wheel you use a piston stop and rotate both direction determining  the center of the two readings .

I can't see how any of this has a thing to do with weather a saw engine kicks back though .

lone wolf

Could just be the nature of the beast you know.
7900                                                               461
046
440
261
200T

Al_Smith

The 038's have a pretty good mag so pulling them over slowly still produces a hot  spark .You have to remember it's coming in at 27 degrees advance factory setting .

Pshaw I've been kicked from anything like a 200T up to and including an 084 .That one hurt me though .It got a D-handle after that by George .

Alta1274


Now I'm confused. Please explain what you mean by a 27 degree advance. The Stihl spec I read in the manual is talking about an advance of 2.6mm BTC at 8000RPM . That translates to about 2.6 degrees after doing the math since the circumference of my flywheel is 358 mm and obviously there are 360 degrees in the circle. Did you mean 2.7 degrees, or does the ignition module automatically advance the spark to 27 degrees at cutting speeds? What are the 038 engine RPMs at cutting speeds? Seems like a lot of advance.  ???
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

joe_indi

The elasto start system may not be a very good idea if there is more-than-usual lash.
The 'Elasto' bit actually enhances the chances of back fire. A solid grip might be safer.
As part of the cure for saws with this problem changing from Elastostart to plain grip is what I do for customers.

ZeroJunk

Quote from: Alta1274 on November 04, 2013, 11:44:57 PM

Now I'm confused. Please explain what you mean by a 27 degree advance. The Stihl spec I read in the manual is talking about an advance of 2.6mm BTC at 8000RPM . That translates to about 2.6 degrees after doing the math since the circumference of my flywheel is 358 mm and obviously there are 360 degrees in the circle. Did you mean 2.7 degrees, or does the ignition module automatically advance the spark to 27 degrees at cutting speeds? What are the 038 engine RPMs at cutting speeds? Seems like a lot of advance.  ???

Several of those vintage saws are in that 20 degree plus range and the timing is fixed to run well at working speed . Newer coils start closer to TDC for easy starting and advance with RPM.

WidowMaker

Well I finally decided to take a look at mine.
Air gap was almost non-existant. reset that and now it starts
on the first or second pull, no sign of kick back...

Hope you guys find a simple cure for yours....

Al_Smith

To clarify things most chainsaw engines no matter how old they are will be in the 25 to 27degree before TDC spark advance .Some over 30 degree advance believe it or not .--Lombard Comango --

Those listed in MM or fractions of an inch before TDC will still fall within those parameters .I pointed out before on a degree wheel close to top or bottom center the degrees change rapidly because of the relationship geometrically of the crank throw near the bottom of a circle .It gets confusing at times .

Al_Smith

More .--This thing shuts you down on a long post so rather than fight it I give in two or three .More than one way to skin the same cat . ;)

So back to 038 mag ignitions .I don't think they are of the self advancing type like the 042 and 048 but rather fixed at 27 before unless the key has been filed or the lamenations altered to shift it .They are  as  I have said a hot coil and it doesn't take much movement or great speed of rotation to get a hot spark .If you dilly dally pulling it over you will get jerked around .

If you think that one is bad try a 2100 Husqvarna some time .

Alta1274

Quote from: joe_indi on November 05, 2013, 09:34:05 AM
The elasto start system may not be a very good idea if there is more-than-usual lash.
The 'Elasto' bit actually enhances the chances of back fire. A solid grip might be safer.
As part of the cure for saws with this problem changing from Elastostart to plain grip is what I do for customers.

Several of those vintage saws are in that 20 degree plus range and the timing is fixed to run well at working speed . Newer coils start closer to TDC for easy starting and advance with RPM.

Quote from: Al_Smith on November 05, 2013, 08:43:26 PM
To clarify things most chainsaw engines no matter how old they are will be in the 25 to 27degree before TDC spark advance .Some over 30 degree advance believe it or not .--Lombard Comango --

Those listed in MM or fractions of an inch before TDC will still fall within those parameters .I pointed out before on a degree wheel close to top or bottom center the degrees change rapidly because of the relationship geometrically of the crank throw near the bottom of a circle .It gets confusing at times .


I hear you all. I have ordered the full 92 page 038 magnum service manual so I can get the factory ignition info for the magnum. I have been working with an older more abbreviated 72 page 028/038  (I assume pre magnum) manual.   I want to see everything the factory has to say about a magnum ignition. Perhaps they might even mention a dwell spec. Which I was apparently mistakenly calling lash since I did it at BDC and did not lock it at 90 degrees with  piston block. When that comes  I can remove the chain, clamp the bar in my shop vice, put a timing light on it to see exactly what I have going on. I am learning more and more from you all and hope to get to the bottom of this bothersome issue if at all possible.
Thanks again all comments are appreciated. :) :)
Bob
Stihl 038 Mag 
MacCat 38cc
Huskee
22Ton hor/vert splitter

Al_Smith

Well Bob you'd have to have a very fast timing light to see anything because they can wind up to over 12,000 RPM if stock and several more if modified .

ZeroJunk

You can Google "how to check chainsaw timing you tube" and you should see one where Brad Snelling does one with a timing light.  But, it didn't look like he revved it up very much. I assumed that whatever advance it had would show up at relatively low RPM since he marked idle and throttled up and there was quite a difference. If the 038 has just a fixed module it should be the same at idle.

Al_Smith

Someone else had a vid clip of using a light in addition to Bradley David .I can't remember who or what saw though but it showed a fixed and a self advance type coil .

There really isn't much info on self advancing coils .The only info I have is on the 048 .Even at that I'm not certain if it's a fixed advance or variable with RPM's .It works something on the voltage rise of the trigger circuit which would increase with RPM's . I'd have to read over it again to even attempt to explain it .

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