The Forestry Forum

Hi all,
I have a Stihl 031AV in the shop because it wouldn't start.  They rebuilt the carb and changed the points/condenser module over to the electronic version.  It now runs but shoots about a 6" flame out of the exhaust.  The tech said it is timing and the only thing left that it can be is the coil.  It is my understanding that coils rarely go bad so I was wondering if any one has any experience or insight into what else could be the cause of this.  With the lack of parts availability and the increasing age of this unit I am questioning the wisdom of continually pumping money and parts into this trying to keep it alive so if there are several other possible causes it might be time to cut my losses.  Thanks in advance for any replies.

Well I suppose you could use it for a flame thrower if nothng else . :D

Seriously the only time I ever saw a flame shooter was one that had serious cylinder damage and it certainly wasn't 6 inchs of fire .If it was timing the thing would be firing so late you'd be lucky to get 3 thousand RPM's out of it .

Now I have no idea what type of solid state trigger device said shop used to replace the points but there are several .The most popular uses the maximum amplitude of the sinosoidal wave form and fires when that is at it's maximium which should be around where it would fire using  a set of points .

Others might use a triple pick up type of trigger that works in conjuction with the flywheel magnets .As a rule though that type requires a different configuration of the magnets .Thusly a different flywheel .

Aha ,detective Smith on the job .Herein might be the problem .It appears the points system in fact uses flywheel part number 113-400-1200 .

However the solid state trigger used part number 113-400-1201 .Sooo if said shop did not change the flywheel and used the replacement Stihl trigger device they have done you a disservice or so it would appear .The coil is the same on this model irregardless of points or trigger so the coil obviously is not bad else you wouldn't have a flame shooter .So much much for "gold level " Stihl factory trained mechanics . ;)

What Al said.

I will add that I have seen a few bad 031 and 032 coils.  Sucks as they are not able to be replaced with other versions due to the special mount pattern.  If yours makes sparks, I HIGHLY doubt that it is bad.  When they die, you will get ZILCH out of them for sparks. 

Lets have some more info on what trigger you have and a P/N from the flywheel if possible.  Pics would help as we need to see how it it mounted.  Pobably best not to run it until we solve the problem.

I had a flame-thrower MS-290 once.  It was run on 100LL avgas, and had a little ball of lead grounding the spark plug intermittently.  I guess the spark screen is not intended to stop flames.......

I would like to see a pic of this thing throwing that big of a flame out its exhaust. :o

Gives a whole 'nother meaning to a "fire"wood saw, huh?  :D