Stihl 029 super runs until turned on side

[redtom]

My BIL dropped off his saw. It runs until you turn it on its side. His repair man said it was burned up and would cost more to fix than its worth. I havent had a chance to look at it but am familiar with my 028's one of which i have rebuilt. Any suggestions before i dive in?
 

[2x4]

the vent hose coming out of the gas tank, underneath the air filter cover, They are supposed to have a small threaded plug screwed into the hose until it is about eighth inch below the end of the hose. Sometimes the threaded plug comes out. Or the vent hose may be split/cracked. Assume it does this when the tank is NOT empty. The vent hose or the internal gas hose are about the only reasons I have seen that they will not run on their side.
 

[Inno]

Sounds like he needs to find a new repair man!
 

[redtom]

That's what I was thinking. Not trying to be lazy without investigating. But, with the holiday stuff going on he just dropped it off. My BIL is not too mechanical and said the guy told him a piston or something was burned up. I know that doesnt sound right if it starts and runs upright. I love Stihl's and I also love proving someones a crook or an idiot, so, I can't wait to dive in.
 

[PJH]

And that little vent hose with the threaded plug that 2X4 mentioned is an off the shelf item at a good Stihl repair shop. I had to replace the one on my 039 a few weeks ago.
 

[Russ from MN]

If it's like my Jonsered maybe the hose in the tank is not long enough.
 

[Inno]

If a piston was "burned up" it wouldn't run at all. Vent tube plugged or fuel intake line is broken or collapsed, could also be that he knocked some dirt loose and the filter is plugged or partially plugged.
Hope he didn't pay anything for the "expert" opinion.
 

[guido]

Hello rdton,
Fill the gas tank up 100% and try it againg.
My guess is the fuel pick up is running out of gas. You may need to make the line longer.
Guido.
 

[Mathias NY]

Consider replacing the fuel line. My MS250 had the same issue from day 1. The dealer checked the fuel line for cracks or kinks but didn"t find anything. I decided to change it anyway and the problem went away. It must have had a weak spot that was sucking air when the saw was tipped. I did need to readjust the carb afterward.

Good luck.
 

[mkirsch]

The 029 is just an upgraded 028. If you're familiar with the 028 it shouldn't be much of a stretch to work on an 029.

It could very well have a scored cylinder and piston. You can burn up a saw in seconds with the wrong carb settings. If you've got a borescope you ought to be able to look in there and see... Also shine a light in the air intake hole, maybe pull the muffler and look in the exhaust port too.

Check compression, do a vacuum test... None of that's rocket science, really...
 

[t.r.k.]

I've seen several Stihls that the fuel line would suck shut. It seems worse since we have ethanol in our fuel.

One other thing: the problem could also be a leaking crankshaft seal. The leak may not occurr until the unit is on its side and the crank moves over a tiny bit. (And the leak itself may be due to worn crank bearings.)

I would do a compression test on the saw before I did anything else. Pull the rope until the gauge quits rising. If it goes to 130-150 psi. it is worth trying to repair. If less, there is a problem with the piston/ring/cylinder.

Some Stihl saws may run at 120 psi, but may be hard to start when hot and the compression is even lower.