Stihl 038 mag problem

[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.

[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.

[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.

[thecfarm]

Alta1274,welcome to the forum.

[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.

[Duane(Pa)]

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.]

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.

[Fatcougar]

Sometimes you just have to scream bonsai and go with it

   Haaahaaa, made me laugh! Too funny.  :D

[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.

[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.

[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 

[Saw Dr.]

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.

[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 

[WidowMaker]

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]

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.

[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

[malce]

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

[WidowMaker]

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

[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 .