Pull cord keeps shearing off (Stihl 038 Mag)

[damien]

Hi folks,

My Stihl 038 Magnum keeps eating my pull-cord inside the housing once I rev to high RPMs. After about 15 seconds of running high, the cord pulley cranks with the flywheel, then the flywheel eats the cord.  This means I usually only get one-pull when I'm in the bush.

Check out the attached picture (below).  I popped off the housing today after running it, but BEFORE the cord was sheared off.

I replaced the pull cord spring (brand new as of today), and I bought the cord in the pic from my local Stihl dealer.

Any thoughts on whats going on here?  Thanks!



    

[beenthere]

Welcome to the Forestry Forum.

I don't have an answer for you, but am sure someone will be a long shortly who will be able to help you out.

The way the pic shows the cord wrapped around, it just doesn't look right. But could be, for all I know.

[damien]

hi! thanks!  yes, the pic shows how the cord pops out of track.  normally it would sit back into the track of the pulley... it does this every time i rev high RPM.

[JohnG28]

Welcome. It looks like you're missing one of the pawls or dogs that engage the pulley to the flywheel. It's the white plastic piece that's in the center, rounded on one end and fit into the metal there. When you pull the cord with it off you can see how it works. Pull slow and the white pawl will swing out, normally engaging the flywheel when in place. There should be 2, one on each side. Missing one you're putting all the stress on one side, and likely deforming the starter. If out of line just a little, it can be then grabbed by the flywheel while running and spun with the engine, which breaks your rope. As long as you put the spring in the right way that's the only possible way I can see this could happen. If you're spring was in the wrong way then the recoil wouldn't pull the rope in at all, so doesn't look like that. As to it popping out, you may have too much rope on there or again, the flywheel is deformed and not holding it in the way it should.   ;D

[sablatnic]

Is it possible to wind the rewind spring one more revolution? Might do the trick.

About the pawls. Don't worry, the 038 use only one pawl. Most of Stihl's saws use one pawl, but have room for two, don't know why.

[HolmenTree]

Like sablatnic said , my guess is you don't have enough spring tension. With the starter off the saw like your photo shows pull the starter rope all the way out to the end with one hand, squeeze the pulley tight with your other hand to prevent it from spinning back, then with your other hand turn the pulley clockwise until the rewind spring bottoms out and stops the pulley.

If you have more then 1 revolution of the pulley the tension is too loose. 1 turn play is proper tension, you may have 3 or 4.

[JohnG28]

I'm pretty sure my 3 all have 2 pawls on them, older ones only have 1?  ??? Don't recall seeing that before.

[joe_indi]

The recommended rope/cord dia for the 038 is 4.5mm. If the present on is thicker it will not wind up snugly onto the rotor. This could cause the outer windings to slip off onto the rotating flywheel.
Similarly the maximum length of the starter rope is 1 meter.If it is longer, it could 'overflow' onto the flywheel.
There should be no slack at the grip end.If there is slack you will need to take it up by rotating the rotor by a full turn.

Regarding the pawl(dog)
Standard used to be only one. But you could install another one, with a change of the pawl spring. Both items are interchangeable with those of the 066/MS660.

[JohnG28]

I still learn something new all the time, sorry to the op here.  : ;D Thanks guys for learning me on this one too.

[mad murdock]

Welcome to the Forestry Forum damien.  I don't have the experience with Stihls that some do on here, but one thing  I know is the Stihl branded pull cord is a tighter weave and lasts longer than an aftermarket alternative.  I leart that the hard way.  I got some hardware store run of the mill pull cord to fix the one on the 075 I was refurbing a couple years back, and it lasted about 15 minutes.  I went to the small engine shop and got the right stuff, and it is still in good shape here now 1 1/2 yrs or so later. 

[cut2size]

I don't know if it will help, but I had a similar problem with an 038 magnum several years ago.  The pull cord would last one start and shear off..  The dealer/repairman took it apart and said that the crankshaft was broken.  It would run like new, but the pullcords were expensive..  It cost more to replace the crank than the saw was worth.  I ended up giving them the saw for the work they did finding the problem.
David

[cut2size]

Eventually I bought another 038 mag from a pawn shop and had to buy parts from my old saw.

[JohnG28]

The saw ran great but had a broken crankshaft? Am I missing something, because that makes no sense at all??

[beenthere]

JohnG
Didn't to me either, but then something maybe to learn from this.
"run like new, but with a broken crankshaft"  ??
Any others know how a broken crank would be the problem here?

[mad murdock]

 ???

[cut2size]

The dealer/repairman said that the crank was held together by such tight tolerances that it continued to hold together He showed me the crank after it was removed.  It might sound crazy but this is a true story.

[JohnG28]

Beenthere, that was my first thought,  maybe I'm about to learn something else here. Still seems way out there to me. Was it a really nice 038? Maybe he just really wanted it?!?  :D I don't see how it could run with a broken crank, or what tolerances would have to do with it. Perhaps had a Crack that wasn't all the way through yet?

[joe_indi]

My first Stihl was a 038 Magnum. After two years of use the saw developed a kind of starting problem.
If I didnt pull fast enough it would backfire. After a while I realized there was some kind of play developing in the crankshaft so that ignition was triggered much earlier than it was supposed to.I filed the holes of the ignition module so that I could retard the ignition a bit. That solved the problem in my 038.