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066 problem

Started by teakwood, August 11, 2017, 08:36:10 AM

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teakwood

I have a 20years old 066 that has been a great saw. Now she is given me some problems. Starts fine and works fine when cold, sometimes when hot she dies on idle and i have a hard time to start her again. have to let her sit a while and start up and stutters until she revs fine. I cleaned carb and fuelintake and still the same sintoms

Time for a new carb? also fuel inlet, pulse hose and ..??
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joe_indi

Maybe it needs a thorough cleaning of its insides, mainly de-carbonizing  of the piston top and cylinder top.
I would replace the pickup body.
A carb kit might be a good idea, since after 20 years the diaphragms would have become stiff. And the strainer would be probably clogged.
The de-carb job would also require a new cylinder gasket.
I think  that would be all that needs doing
Joe

teakwood

Thanks joe
The carb has been overhauled 6years ago, so the diaphragms are not that old. (thats why i suggested a all new carb?)

One week ago i did, carb cleaning, new spark plug, new gasoline pickup filter, cleaned tank vent, new fuelpickup line.

How do you clean out the cylinder? i have done pistons, they are easy. but the cylinder is hard to get in
National Stihl Timbersports Champion Costa Rica 2018

joe_indi

Quote from: teakwood on August 12, 2017, 08:04:41 AM
How do you clean out the cylinder? i have done pistons, they are easy. but the cylinder is hard to get in
How I do it is remove the cylinder, spray some kerosene into it, followed by some dish washing liquid.
I use a steel pot scrubber to get rid of the deposits on the top, inside.
Next I rinse it out with water and leave it in the sun to dry, if I am in no hurry.
If I need it fast I have a stove on Low and place the cylinder on top.
I know its time to remove it off the stove when the top most fins start to just warm up.

snowstorm

Evinrude had what they called engine tuner. It came in a spray can with a connector to the fuel pump. Start it let it warm up then put half the can in it. Let it sit for a hour or so then start again. It would smoke really bad for a while then clear up. It seemed to work. Sea foam is sorta the same thing

ehp

6 years or 6 months ago carb kit ? with todays fuel carb kits need to be done a lot sooner than before . Honestly at a guess I would say you need crank seals and when you do them take a very good look at the crank bearings and make sure they are not spinning in the crankcase, very common thing on clutch side

DelawhereJoe

I don't think there will be any ethanol in the fuel he uses, I think its just an American/Canada thing, could be wrong. Here in Delaware they don't sell non-ethanol fuel at gas stations, possibly only at marina's and the stuff in cans from the stores. So I have to drive to the next state over....about 6 or 7 miles to a station that sells it.
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teakwood

Yes, 6 years ago is correct, but i don't use that saw alot. Maybe 200h in that 6 years.

Would you change carb kit OEM parts or just buy a cheap new carb?  Those cheap carbs worked fine on my 260s.

I don't think that i will split the crankcase, the saw runs super strong, so compression is def. good, so why mess with that.
Just sometimes she will not start at the moment.

we have 2 different gasoline here, Regular with 10 or 20% of ethanol and Super who should be without ethanol and cost a little bit more. Of course i use just super on every gasoline engine i own.
National Stihl Timbersports Champion Costa Rica 2018

HolmenTree

teakwood, in the 25 years I owned my 066 Mag I can't remember ever changing the carb diagrams.

Like ehp said change the crank seals. You don't have to split the crankcase.
While your at it check the main bearings for up and down  play.
The clutch side main bearing got loose on mine. Flywheel side was fine.
Making a living with a saw since age 16.

ZeroJunk

Could be as simple as having your idle set a little too rich. Fine when it is cold, but builds up fuel in the crankcase when it is warm. The stuttering until it clears out when you do get it started would indicate an abundance of fuel more than an air leak.

teakwood

Holmen: ah ok, i thought he meant the seal in the two halfs. now i get it, its the seals in the roller bearings. Can i do them from the outside??

ZeroJunk: You mean the L screw? turn it out (CCW) a little bit?  because the idle on the saw is pretty low, sometimes she dies on idle since this problem, and i have not touched the carb settings in a while.
National Stihl Timbersports Champion Costa Rica 2018

HolmenTree

teakwood, I meant the 2 crankcase seals on the crankshaft stubs, flywheel and clutch side. Just pop them out and press new ones in with a deep socket.

Turning the L screw in will lean and turning out will richer and decrease idle speed.
Making a living with a saw since age 16.

ZeroJunk

Counterclockwise will make it richer, clockwise will make it leaner.  You can set the L for maximum RPM. If it will transition from idle to throttle up without bogging in the transition you can leave it that way. If it bogs in the transition you will need to make it richer so it doesn't starve going to the high nozzle on the outer side of the butterfly which provides most of the fuel at full power. The low nozzles on the inside of the butterfly provide the fuel for idle and have to provide enough that it doesn't just die when you pull the trigger. So, you may have to set your idle an 1/8 or more richer than maximum RPM at idle to get a smooth transition. Sometimes you have to adjust the speed screw that controls the amount of butterfly opening at idle to get the right speed at the mixture the saw transitions the best.

But like I say , if the saw revs fine with the idle screw set at max RPM leave it that way.

Do it with the saw at operating temperature.

teakwood

The saw runs great, revs up perfect, lots of power, high rpms are ok, don't bog at idle.  Just sometimes she will not start and when she does she stutters badly for about 5 seconds until clear up and then runs just fine again. ???
National Stihl Timbersports Champion Costa Rica 2018

ZeroJunk

Could be your needle valve is not sealing properly and the pressure built up in the tank is pushing fuel past it in to the crank case while it sits. Can be caused by a bad seat, worn needle .

Try unscrewing the fuel cap to let the pressure off when it sits, see if it makes any difference.

teakwood

Update:  I did decarbonation as joe pointed out, new cylinder gasket.  Then i did the 2 crankseals and after all of that the saw is still the same, works fine but sometimes dies on idle and the hard to start. i fiddled around the carb adjustment and that didn't change anything ether.

Maybe ZeroJunk is right with his needle not sealing properly theory.

also i noticed that the saw seems to burn to much fuel, more than usual ??? 
National Stihl Timbersports Champion Costa Rica 2018

mike_belben

Get it running, keep it running with throttle and start moving low screw in and out until you get the tone to sharpen up.  There is a "hill" in rpm that you want to find the top of, then go just a tiny hair richer, like 1/16th to 1/8th turn out from peak rpm.

When you land that, back your idle down til the cluth fully disengages and stops walking the chain and saw is stable. 

Now blip to wot a few times. Does it transition right up smooth?   Does it stutter and grumble?  Thats gonna take a tweak on the H screw.  You want it to be a little rough and raspy at wot no load, and crisp and screamy when it dogs into wood.  Pushing in and lifting off in the cut should switch the tone like a 2 stroke dirtbike going on and off the powerband.  When you get that, your H screw is set. 

If you cant get this, its a diaphram or a float tab set wrong or a base leak or impulse leak etc etc.  If the tune wanders during same weather, something is up.  If it loads up and shuts down or wont hot start or wont cold start, yadda yadda. 

On a cold start it should be choke on, pull till it farts, choke in, pull 1, 2, maybe 3 times and braaaaa to life.  If the saw wont cold start like that a day after you get the tune dialed in, look deeper. Check the jug.
Praise The Lord

HolmenTree

Teakwood, like ZeroJunk said metering valve needle.
I'm thinking the metering needle valve fork may be out of height adjustment. Spring could be weak too.
Or the needle's tip may have a worn ring around it from the years of seating.
Also check the impulse hose and rubber intake manifold for cracks and leaks.
Making a living with a saw since age 16.

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