Stihl 034 rebuild

[grin]

First post from a new member.
I have a 034AV that I bought new in September 1985. Most of its life it was used for medium-light work around the farm. Last Fall I cut about 8 cords of 16-20" oak (Wisconsin's oak wilt casualties) during a long weekend. A month later I could not keep the saw running. Last week I brought the saw into a Stihl dealer for a "physical" (what's wrong with me doc?). He pulled the muffler, found the piston and cylinder scored. Said piston is no longer available, so sell saw for parts on EBay. Just like the medical world: do your research and get a second opinion. That is why I'm here.
I'm assuming the Stihl dealer was saying that no Stihl pistons are available and he didn't want to rebuild with aftermarket parts. He also quit his inspection after finding a scored piston and made no attempt to diagnosis why this happened (I always use premium gas and Stihl oil). So I'm assuming I might have a seal leak. With this limited amount of information - what is a recommend course of action?

 

[Bob Hedgecutter]

Unless you own the tooling to pressure and vacuum test the saw, your options are narrowed down to thorough inspection and replace anything suspect, replace the main crank seals as a matter of course.
You will pull the cylinder and ascertain if it is damaged as well as the piston, or if there is transfer from the piston smeared up the exhaust side of the cylinder.
You will have to remove all of any transfer and be sure the cylinder plating is not damaged.
Then you will most likely have to find a piston- genuine Stihl may or may not be available over there for the 034, but pretty sure Meteor do NOT offer a 46mm one, only a 48mm for the 036- so aftermarket?????? You might find various quality Chinese ones- depends how game you are.
You probably can (if you look hard enough) find a good secondhand piston, if your cylinder cleans up.
If it is also damaged enough to not be fit for use- turn the 034 into an 036/360 with a cylinder and piston swap.

Biggest problem you have, is not knowing what caused the lean condition that scored the piston. Could be air leak, could be fuel mix, could be tuning. If it air leak- from where? Pressure and vacuum testing prove where the leak is.

Bottom line is, the saw is easily repairable and easy enough to do with basic tools- but you have (to the best of your ability) find out why it happened and fix it- or it will happen again.

 

[jasent]

Cutting with dull chain can score your piston. Carbon build up etc

 

[grin]

Thank you for all the info on rebuilding.
So I'm trying to determine why this happened. As a retired engineer we always had a "theory of the day" while investigating a failure, until a definitive conclusion was reached. Last October I went down to northern Wisconsin to cut firewood. I primarily cut 12-20" dry oak, which was to be split by the younger generation the following weekend. I brought down a 2-gallon can of premium gas + Stihl oil and a new 'yellow link' Stihl chain. After running through all of my 2 gallons, the saw was still running and cutting great. I was using a 2-in-1 sharpener to touch-up the chain after every 3 or 4 tanks. When I ran out of my fuel, I used what was available. It was supposed to be premium gas + Stihl oil. But I also know that the guy is a firm believer in SeaFoam and had added that to the mix. So my theory: The SeaFoam caused my saw to run lean. Can anyone confirm or refute this theory?
My back-up theory: the last morning of cutting, the fog was so thick that you could practically cut it with the chainsaw. Will really high (100%) humidity cause a saw a to run lean? I'm thinking no. The air filter would have a more difficult time passing air (especially if dirty at all) and the mixture should be rich?

 

[Bob Hedgecutter]

You broke the cardinal rule- Thou shalt not run fuel mix prepared by others in thy saw.
Odds are very good, that is what killed the piston and rings.

Seafoam or no seafoam makes not a lot of difference- oil to fuel ratio does and the fact your saw was not tuned to run on his mix.
You still need to check for transfer on the cylinder walls and any cylinder lining that may be scored through and at the age of the saw you might as well go over all the rubber components with a fine tooth comb so to speak and replace the main crank seals, just because of the fact you are stripping it down and the saw is of a vintage that they should be done while you are in there.
The simple act of using fuel mix of face value quality, not prepared by yourself, or out of your usual trusted can- may have cost you a new topend for a dependable saw.

 

[grin]

You have made a good diagnosis from afar. I am guilty of not seeing this fuel being prepared. I don't know What ingredients were used, How it was mixed (ratio), or When this was done. Three strikes and you are out. Looking back, the saw never ran right again after using two tanks of the other guy's fuel. I always lived by the Golden Rule: Never lend out your saw! I now see that the Fuel Rules are as critical.
My plans to move forward (please comment):
1. Find a reputable rebuilder. I assume a saw shop will have an expert, versus a generic small engine shop. I'd appreciate any western UP Michigan or northern Wisconsin recommendations.
2. Ask the rebuilder to look into replacement pistons. I'm in no hurry, take 3-6 weeks if necessary.
3. IF a piston is available, before ordering it do a complete teardown, inspection, evaluation and get a quote.
4. If a piston is not available, sell the saw. Either the used/parts saw market and let someone else build an 036 or see if there is any value in the vintage saw market (36 years old, made in West Germany, clean one-owner?)

 

[Bob Hedgecutter]

I think my 024 Super is the last West German before the Wall came down saw I have left!

Start another thread on here, there are plenty of members on here that can build your saw back to what it was easily, if you are not keen on doing the job yourself.
Or they could build it back better (360 top end or even ported).
Some of the members here may even have a spare 034 piston in good shape they would be willing to sell you.

If the saw has some sentimental value, could be passed on to a son or grandson one day- get it fixed. The 034 is a good old honest saw and has done you good service over many a season, refreshed it will give you many more.
Selling as parts is not going to raise much to go towards a new modern replacement.

 

[jasent]

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This isn’t a difficult job and it’s one you most likely can do your self with a little coaching. I could do it in a couple hours even splitting the case and replacing bearings but that won’t help you with me being so far away.

For a bit more money you could just replace the saw but rebuilding it your self will teach you quite a bit about the saw. Don’t “need” any special tools really.

Happy to help if that’s the route you decide to go

 

[grin]

Thanks for all the advice. Although I probably have the skills to teardown this saw, I would prefer a rebuild by someone who knows all the little details that make the difference between 'it runs again' rebuild and a 'good as new or better' rebuild. For starting a new thread to find a rebuilder:
1. Is it best to start the thread in "Wanted"? or where?
2. Any suggestions for a title? Need someone to rebuild 034?
Finally, I picked up a used MS290 for my backup firewood saw. Would you sell the 290 to rebuild the 034 or would you just stick with the newer saw and retire the 034?

 

[jasent]

I have a hard time selling saws. Like potato chips you can’t just have one

 

[grin]

I finally got around to doing some research today and now understand why it was suggested to rebuild my 034 up to a 036/360. That seems like a great idea for a primary use as a 20" firewood saw. Thank you for pointing me in that direction.

 

[Bob Hedgecutter]

I finally got around to doing some research today and now understand why it was suggested to rebuild my 034 up to a 036/360. That seems like a great idea for a primary use as a 20" firewood saw. Thank you for pointing me in that direction.

Was mainly suggested as it is easier to find better quality aftermarket top ends for the 036/360 than for the 034.
Has the added bonus of a wee bit more power, but not bucket loads.