Won't idle when sideways

[OneStaple]

Hey,

I have a Stihl 051 that I just started using (after fixing it up) for milling. It starts and runs fine, but when I turn it on its side for milling, it sputters out and dies fairly quickly (when idling), even with a full gas tank. It'll do this even if it's warmed up. However, if it's at WOT, it'll run just fine on its side. So I'm thinking that it's not a gas shortage problem. What would cause something like this?

Another quick question that I think I know the answer to: Toward the end of one of my milling cuts, I felt like the engine rpms started to increase. I think it was due to the gas tank being a little on the low side at that point (perhaps the gas pick-up wasn't submerged completely or something). I filled the tank and I didn't hear the same thing on the next cut. Was being down to about 1/4 tank probably my problem? I'll have to make sure it's always topped off if so.

Thanks!
Tyler

 

[madrone]

I think your 2nd question you answered already, it was probably just low on fuel.
The first issue however, I hate to be the one to offer bad news, but you probably should pressure/vacuum check it for an air leak.
Someone more experienced can probably offer more insight with a few more details.

I saw your photos of the elm milling, nice job!

 

[OneStaple]

I should mention that I just put this saw back together after repairing it. I vacuum tested it just before putting all the outer parts back on, and it held vacuum perfectly.

Any other thoughts?

--Tyler

 

[Stihl #1]

With it off the mill, do a roll out test. At idle with the saw held parallel to the ground, then roll it so the flywheel is up, and the RPM should not change more than a couple hundred revs, then back to flat, then clutch side up, then back. If it changes a lot or dies then you have a bad leak, usually a seal. A minor leak can easily be masked by tuning the carb, but then the next day it will need tuned again or after it is hot it will need tuned again, and on and on. If the saw stays revved up a little after letting off the throttle, then slowly comes back down to idle, that may be an air leak. If you keep cutting with it like this you will score the piston.
When you do a pressure vac test, always do both, and rotate the crank while under vac to be sure the seal is staying tight.

 

[glennschumann]

I had asked a similar question about my 066... I'm planning on getting the crank seals replaced as that seems to be the likely cause. I'll justify it as 'preventative maintenance'. here is a like to the original post

http://www.arboristsite.com/showthread.php?p=1043273#post1043273

Hope that helps