066 stalling

[metalspinner]

I recently bought a used 066 from a tree guy that is going out of business.  He had a twenty inch bar on the saw.  I bought and installed a 36" bar.  While I was bucking a 32" log, the spikes engaged the log and the saw would bog down. When I pulled the spikes from the log, the saw would rev right back up.  I called him up today to ask about this and he mentioned "the carb is set to the 20" bar."  And that I should, "have it adjusted to the 36" bar."  He also said that after it was adjusted to the 36" bar, I should not run shorter bars unless I adjust the carb down.  Otherwise it would "blow the saw."

Can you guy's desifer this advise for me?

[sawguy21]

I am confused as well. It sounds like he was trying to richen the saw to keep the revs down with the short bar but from your description it is running too lean. I would try opening the H mixture screw (counter clockwise) until the saw four cycles (hunts) no load. See the thread on taching for some tips.

[joe_indi]

I  agree with sawguy21.The carburator  seems to be set too lean.
If its a genuine 066 it will have a 3 screw carb without limiter caps.Screw in the H screw to its stop, turn it out one full turn.
Fit your 36" bar and chain to proper tension.
Start up the saw and warm it up by running it at a medium speed.
Take it to full throttle,the engine should run with the top speed breaking up into an uneven burble (four stroking)with a bit of smoke from the exhaust.
If it does not burble, back out the H screw by a quarter turn. If it still does not burble, you need to check for a partially blocked pickup body or mesh filter at the bottom of the carb, or even a in-correctly set metering lever.(latter two best left to a shop if you don't know how to do it)
If the saw does burble, gradually screw in the H screw till the burble stops and the saw runs evenly.Screw it in a bit further and the saw will rev a bit faster.
Now back out the H screw till the saw just starts to burble.This is now the  setting for the 36"bar and chain.
Follow this same procedure to get carb setting  when you use another size bar and chain.

[Cut4fun]

I would also check compression right now before going any further, to know where you were at. You just never know what you might be compensating for.

[metalspinner]

OK guy's.  I now know I should take it to the shop for them to mess with it. I don't want to get in over my head. :-[    It wouldn't hurt to have a professional go over it anyway to make sure it's in tiptop shape.

Is there a chance of "blowing the saw" if I run a shorter bar after the carb is set to the 36"?

It is sounding like I should get an understanding about all of this so I can be self-sufficient in the maintenance.

[sawguy21]

If the saw is tuned to the edge with the 36" you may want to richen it slightly to ensure it does not over rev with the shorter bar.

[leweee]

metalspinner....a Blast from the past.

Madsen's  old website LINK

[metalspinner]

Thanks, Leweee!

That is a good read and now I understand.  I will still take it to the shop this first time. :D

Do I need to make the adjustment with different size bars?  The article did not mention this.

[leweee]

Do I need to make the adjustment with different size bars?  The article did not mention this.

Yes.

[metalspinner]

Well, I'll be...

I went and picked up an owners manuel from the Co-Op today for the 066 and there was all kinds of useful info in there.  Including tuning the carb.  Huh.

It didn't have great sound bites like the above link does, however. ;)  :D

[metalspinner]

I just got back from the Stihl dealer here.
The saw does have an additional problem other than the carb adjustment.  Here is what I can remember from the very patient repair tech's explanation...
The cylinder head has four 6mm bolts that hold the cylinder head on.  One of these bolt holes are stipped and the screw was loose in its hole.  This allowed air and dirt to get into the cylinder giving the saw a lean mixture as well as wear on the cylinder from the dirt.  He does not feel confident drilling out and retapping the hole. He thinks not enough aluminum will be left and the crank case will break.

Of course, with all the dirt and loss of compression the stripped hole has caused, the saw has a limited life anyway.  So I am in a catch 22 here.  Don't fix it (retapping) and kill the saw form dirt and lean mix, or try to tap it and possibly crack the part. :-\

It seems to me this is a simple fix.  What are the odds of the part breaking if he drills out and retaps the hole.  Shouldn't a Stihl dealer be able to do this?  Do I have other options?

[Simonian]

do not retap but heil coil back to original size. a heil coil only increases the hole about a 16th of inch. First you get the correct heil coil and the drill for it. then is all very simple.
You will need to pull the cylinder off to do this right. A new base gasket. Clean out the crank case and put it all back together. Not really that hard. Just get the correct tools

[joe_indi]

The cylinder screw on the 066 is 6mm x 25mm.But the one on the 046(MS460) IS 6mmx30mm.
So, it just might be possible that the threads lower down can hold the 30mm screw.
Fit a new set of rings and cylinder gasket and try using a 30mm screw.
For good measure change the other three screws also to 30mm.
Use thread locking cement and the saw might be usable.
Other alternatives?
1. Its possible to re-tap the hole.I get it done regularly. I haven't had a cracked crankcase from re-tapping the cylinder holes so far.The guy who does the job for me uses a brass insert, which he claims cannot come loose because it expands with the engine heat and holds tightly.
2. Do what a blacksmith would do. Flatten out the threads of a 6mm screw so that it is made a bit over-size.This is pretty crude, but effective if there is no other alternative.

[jokers]

Joe,

What precautions do you take to prevent getting metal chunks and slivers in the crankcase when you have these holes re-tapped?

If I used the 30mm bolts in lieu of the standard 25mm bolts I would carefully roll the engine by hand before starting it to be sure that there are no interference issues and then I would very carefully and diligently watch the saw and listen as I revved the saw on initial start up to be sure that no clearance issues developed while running. I`m not suggesting that using a longer bolt isn`t a good idea but I figure there must be a reason that Stihl uses a shorter bolt on the 660.

[joe_indi]

What precautions do you take to prevent getting metal chunks and slivers in the crankcase when you have these holes re-tapped?

This  is possible by packing cotton waste into the crankcase and around the big end of the con rod prior to doing any tapping.
Once the tapping is over, hold the engine upside down while removing the cotton waste.

If I used the 30mm bolts in lieu of the standard 25mm bolts I would carefully roll the engine by hand before starting it to be sure that there are no interference issues and then I would very carefully and diligently watch the saw and listen as I revved the saw on initial start up to be sure that no clearance issues developed while running. I`m not suggesting that using a longer bolt isn`t a good idea but I figure there must be a reason that Stihl uses a shorter bolt on the 660.

Well Jokers, you made me rip open the packings of a brand new 066 crankcase and a cylinder to check out the points you had mentioned.
The treads on the crankcase don't go into the inner part of the crankcase, but to recesses on the outer sides.So the longer screws do not present any obstructions to any of the rotating parts.
Re-tapping the treads on the crankcase, if required to be done, will not cause any metal bits to go into the inner side for this reason.
The 30mm screws go down into the  treads up to their end when  about 7.5mm of the thread of the screws are left outside.The thickness of the base of the cylinder is about 13mm.So there is no problem with the extra 5mm in this area.
But, as you had figured, the reason for the 25mm screw is something else. A  longer screw cannot be dropped into the hole on the cylinder.This is because it will be obstructed by the lower-most fin on the cylinder.
This could be  because at this moment I was trying it on a brand new cylinder.
But, on an older cylinder especially when you have a situation like the present one, the hole in which the screw was loose tends to become larger and its possible, with the extra play,to fit the 30mm screw without too much trouble.I have done it several times.
In case the hole is not big enough, the only option (which I had to resort to often)is to drill the obstructive lower fin carefully so that the 30mm screw can be fitted easily.
It  becomes necessary to take some extreme measures to save a crankcase which has only a partially stripped cylinder thread.But if such measures can save a saw, its worth the effort.

[jokers]

I agree Joe, I`d do alot of unorthodox things to save an otherwise good saw. My mother is Scottish and I think this is the Scot in me showing.  :D I`d also have no qualms about boring the holes in the fins larger if that`s what I needed to do to get that screw in there.

[thompson1600]

I'd drill it out and put in a time-sert (or similar insert).  Should still be plenty to drill and put one in.  I have done this on more than one 066 and they hold fine.  Helicoils don't seem to work as well for me but are a still an option too.