Stihl chainsaw 066 died

due to age , id start by seeing if it has any spark in plug , remove plug wire and insert 1/4 bolt , arrange near by a metal bolt or other item (not handle ) and do not hold bolt near item
turn ign switch on (don't bother with choke) and pull engine over several times , observe 1/4 bolt for blue sparks (dim lights if necessary )
no spark present , trouble shoot ign system farther
spark present - remove and clean plug with good solvent
add a little bit of engine start fluid to plug hole and reinstall plug and wire , attempt to start engine , nothing - compession problem or shorted plug if it sputters but doesn't start then its a carb problem , troubleshoot carb (clean it )

I had something similar a long time ago with my Stihl chainsaw. I removed the small carbeurator and found that the gas/ carb float was at times sticking in the open position allowing too much gas to flow into the piston cylinder. The spark and compression can theoretically burn so much fuel on each compression stroke of the piston and the residual ie; overflow of gas/oil mixture is forced out the muffler on the exhaust stroke. Keep in mind the engine is a two cycle stroke engine meaning it fires each time the piston compresses and therefore if it is the float sticking open it will seem like a great deal of raw fuel being forced out the muffler. I hope this will give you a starting point to look at. Good luck and hope you don't get discouraged because the Stihl product, especially the chainsaw is one of the finest produced and on the market today.

Check fuel filter, fuel tank vent and possibly clean carb and replace carb diaphrams

Are you getting a spark..? - NO? check wiring loom from ignition module, check timing gap between flywheel and ignition module, check on/off switch.
Does it have compression.? - NO? then check piston/rings and cylinder
Is fuel getting to the cylinder.? - NO? Carb problem of fuel line issue
More detailed information needed for accurate diagnosis.

Are the poles on your flywheel blue? Are you using an open-air inline spark tester, or holding the plug against the cylinder and turning it over?

Don't mess with the insides of a STIHL carb, just buy a new one. Why put new parts in an old carb?

You are absolutely right, an 066 is a STIHL model chainsaw. Good job!

hi there mwb15
have you made sure the ignition coil is producing enough voltage to fire under compression load ?

you may get a spark at the plug unloaded but under load it may be breaking down / weak making you think its got a fuel problem ?

does your system use a cdi coil system or point/condenser system ?
spark usually falls into weak spark, no spark catergory

if compression , fuel ( you replaced carb) and exhaust are ok , and you have air and vaccuum tight c/cases only things left are timming and spark

remember F A C T S

F = Fuel A = Air & ( air tight c/cases ) C = Compression T = Timming S = Spark

compression should be about 130- 140 approx if in good running order

take a look and let me know

cheers pauly46

You need a new carb, plain and simple. If it runs when you pour it in, the engine and coil are good. It doesn't make any sense to rebuild a carb unless it's like a 2-300$ carb on a large machine. On a two-cycle chainsaw, it's maybe 40-60$ for a new carb, versus a 20-30$ kit, plus labor (yours or theirs) and it's STILL going into an old, worn carb.

Chances are good that the compression is not to blame. I would look at:
1. Bad Fuel
2. Fuel Line/filter
3. Carb dirty/mis adjusted
3. Spark Plug
4. Ignition