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.