Stihl Oil Pump - Worn Out?

[SteveSr]

Hello,

I recently got back one of our trail club saws and after maintaining it and sharpening the chain I went to go check it out in some wood. This is my normal procedure before getting the saw ready for storage or assignment to another volunteer.

This is a Stihl 025 that is setup with a 16" 3/8" LP bar and chain. Although the chain didn't smoke or lock up it definitely looked too dry for my liking (see photo). This was cutting green maple and red oak so no dry, dusty wood to soak up all of the oil. The oil consumption was about 1/2 tank of oil to tank of gas.

When I got home I decided to investigate further. With the B&C removed I ran the saw and didn't see any oil coming from the bar pad. Huh? I drained the tank and it was pretty clean. I removed the clutch and the pump was turning and the worm was intact. There was some indication of a small amount of bar oil behind the clutch collecting sawdust but nothing that I would consider excessive. The only thing left was the pump and pump connection. Unfortunately, the wrap handle has to be removed to get to it.

I pulled the wrap handle and the pump to tank connector was firmly attached and there was no sign of leakage or where the pump could suck air. I also pulled the oil line and pickup and found no issues.

I extracted the pump and the bar pad oil passage was clear. So now I am wondering if the pump is just worn out? The pump showed no signs of clogging. However, there is noticeable wobble/ play in the pump piston. There is also play in the vertical pump piston direction which may have an effect on the pump stroke. I attempted to measure the pump stroke and came up with 0.58mm which is in between the strokes of the two available pumps for this model. However, this may be inaccurate due to the vertical slop in the piston.

My current working theory is that the pump clearances are loose enough that the bar oil will flow back into the tank when the saw is shut off. The pump may also be sucking air around the piston shaft and the vertical slop in the piston may lead to reduced piston travel / oil flow.

Your thoughts?

Thanks,
Steve

 

[cscltd]

The blueing of the bar rail is the heat treat process of bar manufacture-not over heating.
1/2 tank oil for tank of fuel is about normal from what I remember on 025 series saws?Stihl consumer saws had large oil tanks

 

[SteveSr]

The blueing of the bar rail is the heat treat process of bar manufacture-not over heating.

Correct. I mostly posted a photo of the bar and chain to show the dry nature of the chain and the beginning of buildup along the sides of the chain. This chain had so much built up crud on the sides of the links that I did a hot soak (on the stove) in Simple Green to remove the crud before I sharpened the chain (by hand)

1/2 tank oil for tank of fuel is about normal from what I remember on 025 series saws?Stihl consumer saws had large oil tanks

Well, I ordered the higher output (0.65mm) stroke pump to replace the original. Hopefully I can coax it to use more of that oil.

 

[heimannm]

If it adds anything to the discussion, I went through 4 MS250 saws (local county maintenance) last week. All 4 pump a lot of oil and the chain ends up looking very wet. That, and the puddles of oil under the saws when I put them down after test running, I do not have a test log available currently so they are just cutting air...

One saw in particular needed a lot of work.



Mark

 

[SteveSr]

If it adds anything to the discussion, I went through 4 MS250 saws (local county maintenance) last week. All 4 pump a lot of oil and the chain ends up looking very wet. That, and the puddles of oil under the saws when I put them down after test running, I do not have a test log available currently so they are just cutting air...

One saw in particular needed a lot of work.

View attachment 1235123

Mark

Thanks for the data point. I would sort of expect to see oil everywhere if not put in some wood to soak it up but I think that mine definitely has a problem. The only thing left on the list is the pump itself.

 

[muddy42]

I have had very similar issues with a MS460.

- do you have an adjustable oiler, if so set it to max?
- Is the worm gear ok? A common issue is that the metal arm gets loose from the plastic part. If you have any suspicions replace it.
- have you totally flushed out the oil tank with say petrol?
- have you squirted solvent or WD40 through the lines? You should see the fluid emerging in the oil tank and near the bar.
- reassemble the saw then run it and engage brake to ensure the clutch is seated. Then run the saw with the bar off, you should see oil emerging. 1/2 a tank of oil to a tank of fuel is about normal, but you could try a higher output oiler.

Finally I also find some oils are just rubbish. I have had to cut some rotatech oil with diesel to make it lubricate OK.

 

[pioneerguy600]

I have had very similar issues with a MS460.

- do you have an adjustable oiler, if so set it to max?
- Is the worm gear ok? A common issue is that the metal arm gets loose from the plastic part. If you have any suspicions replace it.
- have you totally flushed out the oil tank with say petrol?
- have you squirted solvent or WD40 through the lines? You should see the fluid emerging in the oil tank and near the bar.
- reassemble the saw then run it and engage brake to ensure the clutch is seated. Then run the saw with the bar off, you should see oil emerging. 1/2 a tank of oil to a tank of fuel is about normal, but you could try a higher output oiler.

Finally I also find some oils are just rubbish. I have had to cut some rotatech oil with diesel to make it lubricate OK.

The 025 is a totally different animal from your MS460, the oil pump and drive share no likeness whatsoever but cleaning of the tank and lines is always a good start. 025 and MS250 are clamshell consumer saws while the MS460 is a PRO grade saw with much different construction.

 

[stihltech]

Here we go. It must be the pump. You did clean the hose and the pump slot and bore? The drive wire on the worm does not slip? It does engage the clutch drum?
The connection between the pump bore and the supply hose is the #1 issue. I looks OK? Nope, it always does.
Replace the hose and the connector.
The cheap way ( not recommended by Stihl). Take a SMALL amount of sealer on the oring and flange to the hose. Reassemble, making sure the oring seats in the bore.
I have replaced two pumps in all the time they have been available. Leaks on the suction side and sawdust blockage are #1.
Yes the new pump will deliver more oil IF there are no leaks/ blockages on the suction side.
And don't forget the oil passage plug under the muffler.

 

[hardalada]

10 years ago I replaced the oil pump on my 025...same symptoms...lack of oil.
Prior to that I replaced the clunk filter, checked the lines and cleaned everything, drained the oil reservoir and cleaned it out, and checked the tang/spring....
but the cure was a new (standard) output oil pump. (not sure the high output one existed then)
There is very little oil left in the tank after using the fuel to exhaustion....just like when it was new.