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I killed my Tree Monkey 066 in 6 cuts

huskytime

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My 066 arrived in the mail the other day. I bought it from trooney who said it had about a half hour on it since he got it back from Tree Monkey. I strapped on a 28" bar and chain and it fired up on the 4th pull. I filled it with husqvarna bar oil and the fuel was non ethanol 92 octane mixed 40:1 with stihl oil. I've run about 2 gallons of the same setup in my MMWS 550xp without a problem.

So I warmed it up for about a minute with a few revs and then made 3 cuts to buck a pine log about 18". Oh boy was I impressed, this saw chewed right through it. The idle was low after I pulled out of the cut and it died. I adjusted the idle screw about 1/8 turn to raise the idle and it started right back up. I went in for 3 more cuts and midway through the 3rd it died right mid cut. Now it has so little compression that the decomp valve won't even pop back out when I pull the cord.

I guess I should have gone easy on it for a while longer to break it in.

So, I've never been inside a chainsaw. I've rebuilt a couple 2 stroke dirt bikes so I'm not afraid to jump in there and change a piston. But... I'd appreciate any advise. I was told this one had a 288 piston. Can someone please point me towards maybe a bailey's link for a the right replacement piston? Am I right to be optimistic and think a new piston/ring will get me back up and running? Or should I be on the lookout for other damage?
 

jmssaws

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If it had a half hour on it there's no reason to take it easy on it,it's broke in.

You turned the la in a 1/8 turn?
If it wasn't lean it could only have had a failure of some kind but my money is on it was lean.



I had 3 saws with 288 pistons have the wrist pin bearing fail so I stopped using one almost a year ago.
 

huskytime

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I haven't pulled the muffler yet.

Even before I pushed the decomp it had way low compression.

Any reason why I couldn't/shouldn't put a stihl 066 piston back in there?

Yes I backed out the LA screw about 1/8 turn. I was assuming this was idle as the 2 screws above are high and low carb screws right?
 

Wolverine

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Pretty sure this is the saw we ran while Tom stopped by. He cut a few pine cant cookies, then he let me run it a few cuts in some larger (20-22"ish) maple. She ran fine... in fact it ran really great! I smiled, and that doesn't happen to often w/ a Stihl in my hands. We spent the better part of the evening just chewing the fat, and in that short time I could tell Tom is good people. Not sure if that carries any weight but...

Did it die slowly or an all of the sudden screeching halt die?
I second contacting Scott.
 

huskytime

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I want to be clear I have no ill feelings towards Tom. He is a great guy to deal with and the saw arrived in good working order.

It was a very sudden death like a bog but just bogged all the way dead in an instant mid cut. Like I said the first 5 cuts were awesome, strongest saw I've ever ran.
 

jmssaws

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I want to be clear I have no ill feelings towards Tom. He is a great guy to deal with and the saw arrived in good working order.

It was a very sudden death like a bog but just bogged all the way dead in an instant mid cut. Like I said the first 5 cuts were awesome, strongest saw I've ever ran.
You describe a lean seize exactly.
 

huskytime

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Well I ended 1/8 turn from where I started so I may be backwards... Kinda in shock here. The idle screw shouldn't have caused a lean seize though?

So if it's lean, what should I do when I get this put back together? Is it a high screw adjustment needed to go more rich?
 

MustangMike

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Pull the muffler, and see if the piston is scored, and if so if the scoring is only on the exhaust side or if the intake side is also scored.

Find out from Scott if the piston has been modified. If not, you can often clean the cylinder and replace the piston and be running again.

However, you have to discover why the saw failed. Did you make sure the Hi was tuned to give you some 4 stroking (break up) when you were not in the cut? I would check how far out the Hi screw is.

This could have been caused by an improperly tuned carb, or an air leak. If it was an air leak you must fix it before putting in a new piston, or you will just burn it up again.

Saws that run "too good" are often lean.

If you run a different ratio, or are at a different elevation than the previous owner, the saw must be re tuned.
 

huskihl

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If you run a different ratio, or are at a different elevation than the previous owner, the saw must be re tuned.
Or if it was tuned to the edge at 90° in the summer, and when the new owner ran it a few months later, it was only 50°. Oil in the mix has a higher viscosity when it's cooler and the H jet might require another 1/4 turn out
 

Hinerman

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I want to be clear I have no ill feelings towards Tom. He is a great guy to deal with and the saw arrived in good working order.

It was a very sudden death like a bog but just bogged all the way dead in an instant mid cut. Like I said the first 5 cuts were awesome, strongest saw I've ever ran.

Call me crazy, but make sure the spark plug is tight and make sure the spark plug wire is connected properly.
 

Brewz

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I have had a couple friends ask me to port their saw and the first thing I ask is are you confident in your ability to tune the saw each time you use it and during use.

If the answer is no, then a ported saw is not for them..... as you have unfortunately found out.

Bugger!

A ported saw is running beyond its factory limits and very small changes like temperature, altitude, fuel, tiny air leaks etc make a much bigger difference than in a stock saw that has the "oops" buffer factored into its design.

Porting removes the "oops" buffer.

Think of it like taking a jog along the edge of a cliff.
In stead of running a foot from the edge of a cliff, you're now running an inch away from the edge.
A breeze pushes you 2 inches the wrong way and its all over.

A 288 piston has to be modified to let it clear the crank lobes in a 66.
Also, ensure a good quality OEM Stihl or Husky 13mm wrist pin bearing is used.

I would recommend sending it back to the builder or one of the other members on here with 66/288 experience and have it repaired properly.

In the meantime, read up on saw tuning, buy a tacho and learn to tune by ear, checking the tune with the tacho as you go.

When you learn to do this, fire up that ported 66 and enjoy it!

That's my advice
 
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