Stihl troubles

[jens]

I have a Stihl 034AV with electronic quick stop. It is about 10 years old but has seen little use. The other day it decided to pack up and go on strike.
What happened was I was merely sawing up some firewood when I ran out of gas. I put some more gas in but this particular batch was very heavy on 2 stroke oil. I 'believe' that the saw ran for a little bit afterwards but I am not sure.
At this point, it will not fire under any circumstances
I put a new sparkplug in and tested spark - seems ok.
Compression seems normal.
I have replaced the oily gas with a properly measured mix.
I have tried pouring the fresh mix directly into the carburator to get at least some sign of life - no joy.
I currently have the air filter off and when I poured some gas into the carburator and turned it over, there was a mist/fog coming out the carburator which I do not know if it is normal.
I pulled the flywheel to check points - there are none and the flywheel is now minus one fin
I measured resistance between ground and the coil wire that is used to shut the saw down - 1.2 ohms and of course 0 ohms when the switch is in the off position.
I have NOT tested the electronic blade stop yet as I am not sure if it just stops the blade or also kills the engine.
I would really rather not tear down the whole thing ....
Any thoughts would be highly appreciated.

Jens

 

[blis]

hmmm... lets see...
my fair quess is that your saw is done and its time to buy a husky...

but seriously, you ran it on heavy mix, which itself shouldnt cause anything, other than it might foul the plug and smoke alot, but it should run just fine thou... cant see any reason why it shouldnt start no more...

are you sure the engine turns over properly? might also be worth of trying to bybass the kill swithc...

 

[jens]

What does 'turning over properly' mean ?
The flywheel goes round and round, the piston goes up and down .....

Re the kill switch - as mentioned in my original post, the resistance to ground from the line that goes to the kill switch is 1.2 ohms when the kill switch is not activated and zero when the kill switch is activated. This seems to indicate to me that the kill switch itself works just fine (it's not really a switch but just a contact closure)
What would you suggest I try ?

Jens

 

[sawinredneck]

Two houghts come to mind right away, first pull off the muffler and make sure it's not full of gas, you may have flodded the saw. If it is, dry everything out good and try again. Also look at the pison/rings/cylinder while it's apart. Look for broken rings and scoring.
The other thought I have is a loss of compression, simple, but not acurate test, put the plug back in lift the saw up and hold the starter rope, drop the saw while holding the rope, if it drops to the floor, it's done!!! Time for a new set of rings!
Andy

 

[jens]

Two houghts come to mind right away, first pull off the muffler and make sure it's not full of gas, you may have flodded the saw.

The other thought I have is a loss of compression, simple, but not acurate test, put the plug back in lift the saw up and hold the starter rope, drop the saw while holding the rope, if it drops to the floor, it's done!!! Time for a new set of rings!
Andy

Thanks for the reply Andy,
The muffler was dry and the compression test did let the saw go down but it was definitely not a 'drop'. It took maybe 30 seconds or longer for the thing to go down while gradually creeping past each compression cycle.
There seems to be an excess of oil in the saw as looking in by the muffler you could see tiny bubbles developing from around the piston as it does it's compression stroke.

Jens

 

[Justsaws]

Pull the plug and the muffler and dry out the cylinder with compressed air through the spark plug hole. If a lot of mix mist comes out it may just have been full of over rich mix. If you cannot do that, leave the muffler and spark plug out and balance the saw so it can drain out the spark plug hole overnight.

After it is much drier try again.

Does the piston have any scuff marks on it when viewed through the exhaust port?

 

[fishhuntcutwood]

I have NOT tested the electronic blade stop yet as I am not sure if it just stops the blade or also kills the engine.

Here I think you're talking about the chain brake. If you're referring to the bar and chain as the blade then we're on the same page. No it won't have anything to do with it. It's just a mechanical stop for the chain. You're actually supposed to start the saw with the chain brake on for safety reason.

Just how much oil was in that mix? Like half and half? What do you mean you "believe" it ran, but you aren't sure? Was someone else running it?

Welcome to AS.

Jeff

 

[jens]

Pull the plug and the muffler and dry out the cylinder with compressed air through the spark plug hole. If a lot of mix mist comes out it may just have been full of over rich mix. If you cannot do that, leave the muffler and spark plug out and balance the saw so it can drain out the spark plug hole overnight.

After it is much drier try again.

Does the piston have any scuff marks on it when viewed through the exhaust port?

Ok, I think we have found the smoking gun. I blew out the saw - no appreciable mist coming out. I looked at the piston and it seemed to have substantial scuff marks by the exhaust hole. I pulled the cylinder off and found that there was some scoring by the intake port but plenty of scoring at the exhaust port. The inside is pretty darn clean other than that.
The real kicker .... the scoring on the exhaust port side of the cylinder is substantial enough to trap the rings at that point !

Suggestions on what to do next ? What can be fixed, what needs replacing ? Even in the condition it's in, shouldn't it have at least tried to fire ? Why would it get to the point of not firing at all from running in such short order ?

Jens

 

[jens]

Here I think you're talking about the chain brake. If you're referring to the bar and chain as the blade then we're on the same page. No it won't have anything to do with it. It's just a mechanical stop for the chain. You're actually supposed to start the saw with the chain brake on for safety reason.

Just how much oil was in that mix? Like half and half? What do you mean you "believe" it ran, but you aren't sure? Was someone else running it?

Welcome to AS.

Jeff

Yes, we are on the same page.
The actual amount of the oil in the mix is unknown as I have a habit of just pouring in some oil (yes, i know ... I know ... I know). The gas had a good green tone to it and I suspect the mix was something in the order of 10:1. At 50:1 there is no discernable colour difference to the gas.
I 'believe' because I do not remember for sure. I was running the saw at the time but I am not 100% certain of the chain <rolls eyes> of events ...

Thanks

Jens

 

[Brushwacker]

If you could pinpoint what caused the damage it is possible it might be worth repairing with low cost labor. You could try to find a useable engine off a damaged saw or sell yours for parts. Parts saws usually sell pretty good on ebay if the seller has a good reputation.
My first guess would be your saws air to fuel mix was to lean because your carb wasn't adjusted to the heavier fuel oil mix causing it to get hot.

 

[Justsaws]

Pull the cylinder off and see if it has scuff marks on it as well. Disassemble the saw from the top down.

If the cylinder has very light scuffs you might be able to clean them off and put in a new piston set.

Check the carb boot and impulse hose for leaks(holes, loose fit, etc.).

Was the carb loose?

How many times have you run the saw completely out of fuel?

Perhaps the not enough oil in the mix sometimes?

Was the saw screaming fast the last time you used it?

Good luck. A piston swap is not difficult, just go slow and lay out the parts so you can reassemble it when it is time.

 

[jens]

I would like to thank all of you who tried helping me out with my STIHL problems. I took the piston and cylinder in to a local repair shop and found out that both are beyond repair. Replacement parts would cost around $260 (Canadian). The saw is rarely used any more, has a worn out bar and the chain and chain sprocket are on it's last leg. I have decided that the repair costs are too much compared to a new saw (around $750).
According to the repair man, the severe scoring that was seen in my saw usually results from too much or too little oil in the mix. In my case it would be too much oil as I have always been generous with the oil.
For the kind of use I put the saw to theses days, I might even replace it with an electrically powered saw and be done with all the maintenance issues, It won't be anywhere near as powerful but it is rare indeed that I cut anything over 12" in diameter now.

Thanks again !

May she rest in pieces !!!

Jens

 

[Lakeside53]

Too much oil? Generous? Hmmm... I think the problem was elsewhere...

 

[Rotax Robert]

Too much oil? Generous? Hmmm... I think the problem was elsewhere...

I would have to agree there. kinda like running out of gas due to the fact that your tank was over filled, but short of spending the money for vac/press test as well as a host of other possibilities why waste the $.

rotax

 

[tek9tim]

My money's on a lean out due to empty fuel tank. I did the same thing to a forest service 046 a couple of years ago.

 

[twoodward15]

I am with you tek9tim. What are you going to do with the saw?

 

[jens]

I am with you tek9tim. What are you going to do with the saw?

Things are undecided right now. There is a possibility that a friend has a cylinder/piston set. Beyond that, I will probably sell the remains.

Jens