MS 361 From Hell

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Sam R

8mm Socket
Joined
Jun 28, 2018
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Location
Bloomington, IN
I learned a valuable lesson about the value of one's time... Thought I'd share my ordeal on here.
Customer brings in his 361 says it died in the cut. Ran fine all day but now it won't restart. I actually get it to start when I pull the deco valve out. But I say why don't you leave it here let me look it over make sure it's alright (already thinking to myself it's leaking air somewhere).

Fast forward 2 weeks when after a few back and forth phone calls I tell him I think either the impulse or intake boot may be leaking, evidenced by audible leak nearer to those than the seals. But I have to take it apart to look & plus it's going to cost you this much, proceed? Yes, do it I need my saw for work.

Pull the intake boot (not easy on a 361), it's fine... Impulse, fine. Replace it anyway but use the old boot. Finally pull the clutch & flywheel, thing won't hold vacuum/pressure. Readjust my exhaust block... Still won't hold.
Finally, finally find a tiny amount of bubbling coming from the muffler side screw hole of the oil pump. Think okay, found you. Tried to Dirko the screw hole and while it slowed the leak it didn't slow it enough to consider it a pass.

It's gone way past being worth my time at this point. I can't split that kind of case & once I ruled out everything replaceable I should have been done. Nevertheless I wanted to be able to tell the customer what's wrong with his saw. Still not totally sure what the issue is other than the leak issues from the crankcase somewhere, either gasket (doubtful as I can see no bubbling along the seam) or the case itself has a little hole in it. Saw will run but will probably keep dying in the cut until it gets so lean it seizes up.

The moral of the story: don't turn into Captain Ahab over a chainsaw.
 
I rebuilt one several years ago - and similar situation, it wouldn't pass a pressure/vacuum test. It turned out the PTO side bearing pocket in the case was starting to separate just enough to be a leak.

I ended up having to get a different case.
 
Jacob, yeah I think that's where this guy is at - needs a new case. Not entirely sure where it's leaking just... case half. And Alex, I felt the same but it was more an unhealthy compulsion on my part. Once I ruled out all replaceable parts it wasn't worth my time to continue looking at it. I have a wall full of tools to look at and this took half a day... If it was my saw, different story.
 
Ozhoo, I was considering trying that but I always feel weird about doing that because if water gets in somewhere... I dunno, just phobic I guess.

Duce, I was using a spray bottle of soapy water, looking for bubbling - only thing I found was the little leak behind the eastern oil pump screw. I blew it out with some carb cleaner & dried it then put some dirko in it to try and staunch the leak but it didn't work.
 
Well thanks for the advice there, I'll try that in the future. I've done that with carburetors before, and it's fine... I guess even if water did get in the case you can just clean it out with compressed air.
This saw's had it though, for my time. I found that the case is leaking and since I don't have the tools to split it and the guy didn't sound like he wanted to spend more than half the cost of a new one for a fix, it'll go back to him.
 
I have never seen where water got into a saw case when under air pressure, if they were leaking air and I couldn`t figure out where when testing all the usual places then they got dunked. Found the leak and always split the cases if necessary, never found any water inside. Found cases with cracks and bearing pockets slightly wallered out, a few Stihl`s with leaks around the steel ring in the bearing pockets, tough to find just spraying soapy water.
 

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