Stihl 034 AV 20", Will not cut

Rob-Bob

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Hello Everyone,

I have a Stihl 034 AV 20"

The moment I put a little pressure on saw to cut, the chain quickly stops, bogs down ... and no power to continue. If I try to continue it stalls. If I back off on the pressure, rev up, and try again, same thing. No problem starting or restarting.

Here's what I have done so far:
1) check compression - 145 to 150 every time. Spark plug looks good.
2) rebuilt carburetor & adjust inlet control lever. Reset high speed and low speed screws as per specs. Tried turning them several different ways and combinations and got the saw to seemingly accelerate and idle properly.
3) check muffler for carbon build up
4) replace fuel line, fuel filter, impulse hose, manifold flange

Could a improperly installed sealing plug/plate inside the carb cause the saw to lose power when trying to cut? I don't think I installed it wrong, it just doesn't look professional.

What am I missing? Any ideas may help. Thanks

Rob-Bob

PS What is the easiest way to find this thread when I come back?
 

bertsmobile1

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:welcome:

Chain saw High speed jets have to be tuned "in wood" or if you like under load.

Now before you dive deeper into the saw, is the blade sharpened properly ?
What chain is it running ?
Are the depth stops set for correct depth of cut?

Very common to grind down the bumpers ( depth stops to some ) too far so the teeth cut too deep, put too much load on the engine so it bogs down.
This produces a synario similar to what you are describing , rest the saw on a log and it cuts OK but slow. But put some weight behind it and the teeth then go full depth and overloads the engine.

Sprocket nosed or hard tip bar ?
It all makes a difference.


Shain saws are all about speed, not power.
Very fast speed and a very small cut from lots of teeth.

Arbourist will adjust their saws differently for cutting different wood or even use a different chain.

The blanking plugs will be fine just so long as they don't leak
And if they are leaking it will not make any difference , no load -heavy load the saw will run poorley.
So the important thing is how far off the recommended inital settings did the needles end up being and did you back off the throttle stop when you adjusted the low speed jet.
If you did not the high jet will end up being way too lean ( in too far ).

A little test is if you can turn the low speed jet more than 1/4 turn in either direction without the engine stalling out the throttle stop is too far open and you are sucking through the main as well as the low.
Similar for the high speed . When properly set 1/2 to 3/4 tirn in either direction should kill the engine, if not it is sucking too much through the L jet at full throttle.

To find this thread.
Easy way is to go into your settings and click on the send emails options so whenever some one post to it you will get an email with the post and a hot link back to the thread on the forum.

Next easiest way is to click on your name at the far right side of the screen in the green bar where it says "welcome ********"
That will bring up your profile with 4 tabs , the first being "my activity" which will have a hot link to this thread.
 

Rob-Bob

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Hi bertsmobile1,

Wow, I appreciate all the information. I learned a couple of things.

The bar and chain are brand new Stihl OEM, (sprocket nose and chain recommended by Stihl for the hardwood I'm cutting), bought together as a package. I have about twelve hours on them now. I have sharpened them once when there was more sawdust than chips. No need to touch the bumpers yet. The saw was running great for about the first 10 hours.

I'm not sure what it is you are calling the "throttle stop"? The third carb screw for when the saw is idling? I have had that in all the way, and gradually back out to try to get it to idle.

So... I went back to the beginning and I reset Lo & Hi to one turn out and started the saw. To achieve the necessary rpms I had to turn the H screw in about a 1/2. Only then would it cut a bit. (The wood I'm testing on is a soft poplar) When I say pressure, I mean barely more than the weight of the saw. Then, turning the LO screw in & out 1/4 turn and more the engine did not stall.

One thing I didn't mention before ..... Now with all my experience I hate to admit this for all the world to see.... I absent mindedly poured some chain oil in to the fuel tank. I did catch myself doing that and stopped after about a quarter tank. So I poured that out, shook the saw and left it upside down for a few minutes to get as much out as I could. I refueled with fresh mix and the saw seemed to run fine. I have since run 5 more tanks of gas. I have been cutting wood for 90% of my heating for over 35 years. With this saw I have rebuilt this carb. I have replaced the head and piston. Twice. So I am not a rookie but I have never had this much trouble before. Perhaps you could walk me through the steps of which carb screw to turn first, then second etc. I know this is mostly done by ear but it may help me get this saw cutting right.

thanks
 

bertsmobile1

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Yes Rob the throttle stop is the idle speed, another of thoes two countries seperated by common language things.
We have no idea of the level of competiancy of the person on the other end of the post or those who will read and act on what they have read in the future.
So replies are always pitced to the novice level.

The chain bar oil in the tank will not do any real damage apart from running really oil rich, fouling plugs , gumming rings and will eventually wash out.
We have all done it, you are not alone.

You would never dream of tuning your car by holding the engine WFO in neutral sitting in the drive and chainsaws are no different
The head on a trimmer & blades on a mower put enough load on the engine to tune them but running the chain is not enough load on the chainsaw engine.
So I am told, do enough of them and you can do it by ear, no load, but that is a skill I am yet to acquire.

Sounds definately like your idle screw is in too far and the engine is running partially on the high speed jet at low speed.
Both of the jets will have an effect throughout the entire engine operating range, they just diminish.
readng the manual can leave you with the idea that at some point one cuts out & the other cuts in but this is not the case.

That it why you have to set the high before you set the low then go back & re-adjust the high then re-adjust the low then drop the idle
Once think it it right, put the saw into wood to do a final on the high.
I have seen some cutting with one hand while they are adjusting the saw with the other, again a skill I am yet to acquire.
But cut adjust cut adjust till I am happy works good enough for me.
when you are happy with the cut then go back & re-adjust the low to suit the high.

You will know when the low is correct from what I siad in the previous post 1/4 turn either way to stall out is spot on, 1/2 turn either way acceptiable any more and the idle screw is too far in.

And are you sure you sharpened the chain properly ? did the shop tell you to use a different file or guide angle.
Stihl generally put that info on the saw chain combo packs but if it is ifferent to what you have been doing it is easy to get the angles a bit wrong,
I use a diamond wheel and it takes 3 times as long to set the girnder up than it does to actually sharpen the chain.
 
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