034, not running proper, any help?

[RAY_PA]

So I was helping my step-dad this weekend and in the back of his barn sits a Stihl 034 that looked like it has been sitting there for quite sometime. I asked him why he hadnt been using it..."last time I did, was several years ago. It would run good for about 30 min, then bog down and quit. Let it cool down and it would run good for a short time again. So I set it there and forgot about it."
Well, sure enough. I take it home, clean it up real good, sharpen the chain, give it new gas and bar oil and get it running. runs like a champ and cuts great, for about 20 minutes, just like he said. Felt like it was bogging down bad, then stalled. I started it back up and same thing.try to start it again and it seemed like it was starving for fuel, when it did fire, it would rev up real high and die almost as fast.
Any ideas?...I dont have a clue...
Thanks, Ray

 

[HittinSteel]

I always start with simple fuel line and new filter.

 

[Jags]

Fuel line getting warm and collapsing on ya (just a first guess). Rev real high is a lean out response to no fuel.

 

[RAY_PA]

OK, I have never replaced a fuel line/filter is this something I can do? And if so, what do I need and need to do?
Thanks

 

[HittinSteel]

post # 27 is how I do it

https://www.hearth.com/talk/threads/which-saw-to-get.69104/page-2#post-868995

 

[lukem]

Gas cap may not be venting very well either. 30 is a bit long for this problem to manifest itself, but it is easy enough to check.

 

[amateur cutter]

When it dies out, try loosening the gas cap for a few seconds, then re fire it. Sounds like a possible tank vent problem. Yes you can replace the lines pretty easily in that saw, look in the tank to see if the fuel pick up/filter is moving freely as well. A C

 

[MasterMech]

Fuel line problem wouldn't take 30 minutes to show itself. The tank vent could be plugged. Try removing it after the first time the problem shows up. Easy to do in the field.

034 should receive new fuel lines/filter and have the vents checked out before going back into battle at this point anyways. Saw was around before ethanol in our fuel and what may have been a marginal fuel line will fail sooner rather than later.

I would also recommend checking the carburetor diaphrams if the tank vent checks out ok.

Also, and this is a long-shot, but my 034 had a cracked plastic fitting on the carburetor inlet. (Orginal Tillotson carb) I highly doubt it would take 20 min for that to start causing problems but just something to keep in the back of your mind.

 

[bluedogz]

This describes almost exactly the troubles I had with my saws AND my weed whacker AND my tractor. Started adding blue Sta-bil to all my gas plus new spark plugs all around, and poof, no more problems. I understand the trouble is the ethanol in the gas. Ethanol started being used more commonly in 2007, which kind of jibes with the origin of your dad's troubles.

 

[ScotO]

I just now was working on an old Homelite with basically the same problems. Turns out the filter screen on the pump side of the carburetor was CAKED with junk, I mean totally packed full on the inlet side. Rebuilt the carb, installed and immediately looked at the filter in the tank. It was one of those 'stone' filters and it was totally trashed, which led to the crap getting into the carb. Cleaned out the tank, installed a good STIHL filter, and the saw runs like a champ now. Anytime a saw sits for a long, long time, you GOTTA give the carburetor a once-over. You can almost be guaranteed it needs it.