Stihl 066

[Brian1]

Hi All,
Writing from Brisbane, Australia. My first Post.

I was very pleased to get my hands on an inexpensive 066 flat top, red light recently.

Not very loved by previous owner – a few stripped threads, wrong muffler, neglected clutch and thus damaged oil pump. All those items fixed/replaced - worthwhile with a cylinder compression of 150psi. (I don’t have the tool to measure crankcase compression). Engine started and ran well.

So yesterday I applied the saw to a felled hardwood 2ft trunk, using 25 inch bar.

Cut well to begin with but made a popping noise (not backfire) and as soon as I stopped cutting the engine abruptly cut out. After the 2nd time of this I grabbed a screwdriver to adjust the idle speed (although it had seemed fine at the beginning).However the saw would not start, the engine was spinning too easily with the pull start as if there was little compression.

Later on the workbench I saw that as I pull started, fuel was running down the crankcase from behind the muffler. So I stripped down the plastic shrouds and the muffler. Sure enough as I pull the starter fuel pours out of the exhaust port. The compression with no muffler is 100psi. I have spark but of course when in the cylinder the spark plug is flooded.

I haven’t come across this issue before, hopefully it is the carburetor (Walbro). Guidance would be much appreciated please.

 

[rmh3481]

Usually when a carb leaks fuel into the cylinder its the inlet needle inside the carb that is not sealing. Sometimes all you need is a new carb kit with a new needle and new diaphragms. Other times you will need a new carb because the inlet seat wears. Polish the seat with a qtip dipped into silver polish and clean everything well before reassembly. For the compression problem, from what you describe its sounds like something let go and until you take it apart you wont know. A backfire like that 'pop' will sometimes indicate a fractured piston skirt.

 

[stihl for life]

Sounds like your carb is pour fuel into your case. Open up your carb and check to see if everything is in there and clean . make sure your metering leaver is flash with the carb .

 

[blsnelling]

Better check you piston with compression that low. Pull the muffler.

 

[Brian1]

Many thanks for the replies. In view of the remarks I have pulled the cylinder before dismantling the carburetor.
Pretty disappointing and ugly. Someone has been there before me. One of the crankcase threads to receive the cylinder bolts has been stripped. A nail was rammed into the hole and a smaller diameter bolt cut into the resulting smaller hole! Looks like a helicoil will put that right but an ominous start to the strip down.
Please see photos for the piston and bore. Big gouge in the piston with corresponding gouge in the cylinder bore, beneath the inlet port. Strange damage to piston top and rings. Any ideas to the cause? I take it that the cylinder is toast as well? No evidence of piston metal buried in it.
Should I wash out the crankcase in case there are any metal particles fallen in? The big and small end bearings have no slop in them so I don't intend to split the crankcase.
The cylinder looks to me as if it has been shaved off around the bolt mounts? - see pic.
So, not my finest buy - goes to show what can lurk below what appeared to be a halfway decent saw. Good job it was cheap - but it won't be by the time I've finished spending! Ho hum, carburetor next.

 

[blsnelling]

Uhg!!! Piston and cylinder are ruined and case is damaged. You might be finished before you got started. This is why I advise to always go through an older saw that you plan to work with. You basically bought a totally trashed saw. Too bad you already replaced several bad parts.

 

[stihl for life]

O **** thats one f up cylinder

 

[rmh3481]

Have you seen these;
http://www.ebay.com/itm/NEW-ENGINE-...wTvIoAncFEjgp%2B8u6ws%3D&orig_cvip=true&rt=nc

 

[wyk]

You need to take some nails and screws to the guy that sold that to you.

Don't despair, though. Now you can contribute to another thread we have:

http://www.arboristsite.com/community/threads/stupidest-repairs-ever-witnessed.173229/