Stihl MS390 spitting bar oil everywhere...

[Mike Kunte]

Hello all!

Been enjoying your site for a while now - great info and some very knowledgeable guys here!

I have an issue with a 12 year old Stihl MS390. As backup saw to my MS361, she does regular housework, idles well, picks up fast, runs like a demon, and starts first time, every time. However, lately she has been spewing bar oil from inside the sprocket cover. It's so bad that after about 1 minute's worth of running, the bar oil comes oozing out from the sprocket cover - top, bottom and sides. Completely coats the inside of the sprocket cover, clutch assembly and everything else inside. Bar throws off oil too (good), but I am concerned that all this oil will eventually work its way into the clutch and cause problems there. Of course, I'd also prefer 98% of the oil to go to the bar and chain!

I use only Stihl bar oil, but as you can imagine, she now leaks this oil all over the place when standing...

Stripped her down and cleaned up the oily mess inside (as you can imagine). Problem persists...

Please let me have your suggestions for a solution.

I've tried the following:

1. Turned the oil feed down (counter clockwise) to minimum setting. (prefer it a bit higher, but just for testing). No go!
2. The inside plate against which the bar sits where the oil hole lies in its groove, has a slightly raised lip, to seal against the bar. I made a temporary gasket (using a glue gun and bolting the bar in place) to see whether the leak may have been between the bar and the lip. No go!
3. Ran her without sprocket cover (used spacers to bolt bar on) to see whether there is an obvious leak anywhere. No obvious leak - just a lot of oil spray from around the sprocket. No go!

Nothing has made a difference, though!

Thanks in advance,

Mike

 

[Wyatt183728]

I had this problem in my 028. I used a 50/50 mix of bar oil and vegetable oil and for some reson the problem fixed itself. Are you using a wintry mix bar oil? its thinner and would spread alot more.


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[Mike Kunte]

I had this problem in my 028. I used a 50/50 mix of bar oil and vegetable oil and for some reson the problem fixed itself. Are you using a wintry mix bar oil? its thinner and would spread alot more.


Sent from my iPhone using Tapatalk

I had this problem in my 028. I used a 50/50 mix of bar oil and vegetable oil and for some reson the problem fixed itself. Are you using a wintry mix bar oil? its thinner and would spread alot more.


Sent from my iPhone using Tapatalk

Hi, Wyatt!

No, straight Stihl bar oil. BTW, we don't really have Winters here in South Africa. It's around 23 deg C here in mid-Winter...

Mike

 

[Wyatt183728]

Since your saw is older, your oil pump may be worn out, Mike. It might be a good idea to check that out and if needed replace it. Im no expert, but this is what comes to mind.


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[HarleyT]

3. Ran her without sprocket cover (used spacers to bolt bar on) to see whether there is an obvious leak anywhere. No obvious leak - just a lot of oil spray from around the sprocket. No go!

Well, if it is not coming from the channel up where it mates to the bar, then you know where the problem is.....

 

[HarleyT]

Here is the oil pump.........

The white plastic arm is the output side going to and fastening to the little white tit is on the crankcase, start looking there.....

 

[Mike Kunte]

Thanks, Wyatt.

Just a thought - would a new pump not make the problem worse? I already have too much oil, even with the old pump.

 

[Mike Kunte]

Thanks, Harley!

Do I understand you right? Do you mean that the white plastic might be cracked or something? Whilst the saw is running (with the bar off), I close off the oil channel with my thumb, and no oil comes out anywhere.

 

[HarleyT]

Thanks, Harley!

Do I understand you right? Do you mean that the white plastic might be cracked or something? Whilst the saw is running (with the bar off), I close off the oil channel with my thumb, and no oil comes out anywhere.

Well, that kinda don't add up... Can you take some pics and put them up? Show us a pic of the area where the bar would sit, etc.

 

[Mike Kunte]

Well, that kinda don't add up... Can you take some pics and put them up? Show us a pic of the area where the bar would sit, etc.

Well, that kinda don't add up... Can you take some pics and put them up? Show us a pic of the area where the bar would sit, etc.

Here are the pics. As you can see, oil, oil, and more oil! That was about 1 minute of running.

 

[HarleyT]

When idling, is the chain moving?

 

[Mike Kunte]

No, no movement of chain at idle. Only when revs pick up.

 

[HarleyT]

So it keeps oiling without the chain moving?

 

[HarleyT]

When idling with the bar/chain removed, the sprocket will still rotate a bit, thus pump a bit. It sounds like you have a
bar/saw mating flaw/gap, allowing oil to dribble out in the clutch area.

 

[Mike Kunte]

Hello Harley,

Thanks for all yourhelp so far! There is no oiling when the chain is stationary. This is normal. You are right though, that, due to a little clutch friction, it will rotate and thus pump oil with the bar and chain assembly removed.

In my original post I did mention that I had created a "temporary glue gun gasket" around the oil channel for testing purposes. This can be seen in the 1st and 2nd pictures as a thin, oval, translucent layer around the oil channel. Despite this seal, there is still a huge amount of oil between the bar and saw (this can be seen on the picture of the bar). That is why I can't understand where the oil is coming from.

Whilst running with the sprocket cover off, I did notice a lot of oil running down the sprocket side of the bar, i.e. where the chain "enters" the bar on its forward movement (marked "A" in the pic), running down towards the "bottom" of the bar where the chain "exits" on its way back to the sprocket (marked "B" on the pic). From here it could easily be flung around the inside of the saw by centrifugal forces.This is puzzling - the oil should be going "forward" with the chain. Bar is relatively new, and chain is in good nick. The "tangs" are complete and well-defined, so they should have no problem "picking up" the oil on their way forward.

The new Stihl bars seem to have "forward angled" oil holes. Perhaps I could try and Dremel this angle in to the current bar to encourage this forward motion?

If this does not work, I'll fabricate an attachment for my cordless drill to run the oil pump with the clutch assembly removed, to make sure that there is no oil being ejected from "behind the scenes" in the oil line.

Regards

 

[pgdalton]

You said relatively new, did the problem start when you replaced the bar?

 

[Mike Kunte]

Pg,

Can't say exactly, but I'll try with my spare bar and give it a go.

Thanks for your input!

 

[Mike Kunte]

Ok, pulled the pump. Since this must be a pre-2002 model (older than I thought), the "plug" does not appear to be present. This could be the culprit. Furthermore, all 3 O-rings seem worn out. Since a new pump is almost $70, I'll try the 50c route first....

Will keep you posted. Comments highly appreciated!

 

[Sepia]

If you put a .050 guage chain on a .063 guage bar, I could see where oil could flow backwards past the forward moving chain.

 

[Mike Kunte]

If you put a .050 guage chain on a .063 guage bar, I could see where oil could flow backwards past the forward moving chain.

Thanks, Chris!

Agreed. But it's a genuine 0.063...

I'll keep at it!