Strange Case Hole in Stihl MS 310

[Wood Doctor]

I seldom initiate threads but this discovery really caught me off guard. Bar oil started leaking out of my Stihl MS 310 from this strange hole that I found:

I don't have the MS 310 IPL, but I checked my MS 290 IPL and saw nothing there. Next I contacted an 031 owner who also said his had no such hole in the case. I also cannot find one on any other Stihl saw that I own. Bar oil does leak out, and I thought that it might have at one time been a Stihl bar oil tank vent idea that went haywire. As it stands, bar oil could drip right onto a hot muffler. The oiler is otherwise working fine.

Anyway, I am tempted to plug it with a machine screw and gasket cement. Anybody have any ideas or comments?

 

[HarleyT]

Yeah, it has been covered a lot.

 

[blsnelling]

That comes Fref the factory with a plastic plug. Stihl will sell you a threaded grub screw.

 

[HarleyT]

https://www.arboristsite.com/commun...aks-oil-out-the-maincase.146275/#post-2407348

 

[Wood Doctor]

https://www.arboristsite.com/commun...aks-oil-out-the-maincase.146275/#post-2407348

Dang, I should have done a thread topic search. Thanks Harley, Brad, etc. I'll fill it back up. Likely this was an early release of the MS 310. I rebuilt this saw with a 390 top end. A tree service manager handed it to me in pieces and said, "Edwin, it's all yours. One of our workers destroyed it."

It's been a good loaner and I usually keep it for that because I seldom prefer it over my MS 361 or a couple of others I have in the arsenal. I'm sure you can understand that.

I used a #10 machine screw, 3/8" long that I had in my parts cabinet. Looks like it works very well. The threads grabbed right in. Bar oil leak is now nil. Thanks all.

 

[Stihldoc]

Great fix!
If you installed a -390 top end on this saw, you may want to consider replacing the fixed jet in the carb with the -390 jet. I don't remember the inside diameter of the jets. I did lots of this upgrade on Fire Dept saws 10-12 years ago and I found that they ran OK with the -310 jet in them, but ran better under a load with the -390 jet.

 

[Wood Doctor]

Great fix!
If you installed a -390 top end on this saw, you may want to consider replacing the fixed jet in the carb with the -390 jet. I don't remember the inside diameter of the jets. I did lots of this upgrade on Fire Dept saws 10-12 years ago and I found that they ran OK with the -310 jet in them, but ran better under a load with the -390 jet.

I will look into that. I like this saw for a couple of reasons: (1) I salvaged it from a box of scrap parts that a tree service company gave me. They beat it up and thought it was trash. It wasn't. (2) Last month I lent the saw out and the operator burned out the clutch bearing and two of the clutch springs by overheating it. I fixed that. (3) Now it always starts and runs. This saw started last week on the third pull when my MS 361 became hesitant. Sometimes my 361 acts like a spoiled child. The 390 was anxious to prove itself once again and fired immediately. I'll never loan it out again.

Thanks, StihlDoc.