After owning a Stihl MS260 for about 15 years I've recently been getting less oil flow. Tried adjusting but couldn't get screwdriver to locate in anything. Just got a little camera & find there is nothing where I expected the oil adjustment screw to be. Any ideas on how this could be or what I do to rectify? The metal scratches are where I was trying to locate a slot with screwdriver.
No oil screw?
- Thread starter Mozzer
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Some had a fixed oil pump, pull the side cover and clutch off to investigate.
https://store-wgfoazho0n.mybigcommerce.com/content/Stihl MS260 MS260C (1121) IPL.pdf
https://store-wgfoazho0n.mybigcommerce.com/content/Stihl MS260 MS260C (1121) IPL.pdf
Thank you very much. I'll stop looking for the adjustment that doesn't exist. Mine doesn't have it, first time removing the clutch, will look for a new kit & some instructions as I imagine a lot more stuff needs to come off to run the lines to tank & feed etc. I would have removed it to investigate the insides but wasn't sure how the brake spring comes off. Haven't got a spare saw so have to be careful with dismantling too much while still in wood gathering season.
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SteveSr
Addicted to ArboristSite
These oil pumps can clog up from crud (sawdist, etc.) that is sucked in through the intake screen. This reduces the pump piston travel and the oil flow. Since the pump runs all the time these saws tend to get covered with excess oil. How much oil is used per tank of gas?
It's using about half a tank of oil per tank of gas, up to now was consistently just a bit under a tank of oil which was perfect.
The screen looked clean but I guess smaller sludge could have got through it & built up. I will investigate further on how to remove the pump as the worm & drive gear looked fine.
SteveSr
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Half a tank is too little for that continuous oil pump. Almost a tank is about right. BTW, have you changed you oil brand lately?
The adjustable metal pumps could be disassembled (with some effort) and cleaned. The plastic ones you would have to figure out how to non-destructively remove the metal plug from the end of the pump.
Don't know if you could hold the piston back far enough to shoot some brake cleaner all the way through the pump. You would probably have to move it right (in your photo) about 3/16".
The conversion kit to the adjustable pump looks like quite a job, maybe I'll try a replacement with same as original as it's lasted this long. Just got to see how the brake spring comes out. Haven't changed oil type but after the problem I did try some extra thin stuff, made no difference.
SteveSr
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The conversion kit is NLA for quite some time unless you know a private source.
Brake band is easy. Outlet hose not so much.
1. First, dump the oil tank into a clear glass jar and let it settle for a few days and examine any crud in the bottom of the jar.
2. Dump some old mix or kerosene into the oil tank put the cap back on and shake. Dump this into another glass jar.
3. Repeat #2 for good measure.
4. Remove the oil pump screws and bend the outlet hose so that the pump inlet faces up.
5. Spray some brake cleaner into the inlet hose to make sure that it is clear of crud. and check the tank again for debris.
5. Get a helper you'll need 4 hands for this. Hold the piston back against the spring as far as it will go Have your helper try to force some automotive brake cleaner into the pump inlet and see if it comes out the outlet about the same volume that goes in. If so you have probably flushed out the pump. If that doesn't work try #6.
6. While the helper is spraying brake cleaner try rotating the pump piston while holding it against the spring. This may allow enough flow through the pump to clear it. The pump has a rotating valve which prevents a straight shot through the pump.
7. If this is successful reinstall the pump and test it.
8. Get a 1" chip paint brush and trim the bristles flat. Use this to remove crud from around the caps before you open them.
Just to check #5, the worm drive gear shaft should push into the pump like sketch below?
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SteveSr
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My bad... Stihl had several different pump designs over the years and I was thinking that the spring was on the other end of the piston allowing the piston to be pushed back out of the pump. The one in the photo is the opposite. The objective would be to move the piston AWAY from the pump inlet and outlet end.
If you can't do this the next best thing is to rotate the piston while trying to force brake cleaner through the pump (#6 above).
See that flat on the end of #17 in the photo. That is the rotary valve.
If you can't do this the next best thing is to rotate the piston while trying to force brake cleaner through the pump (#6 above).
See that flat on the end of #17 in the photo. That is the rotary valve.
Try running a couple of tanks using a mixture of 3 parts diesel (or kerosene) to 1 part bar oil.
The diesel or kerosene should help clean out any thickened residue and may get it pumping pretty normally.
The diesel or kerosene should help clean out any thickened residue and may get it pumping pretty normally.
I've also ran that mixture with Marvel and diesel. Run it then let it sit a few hours, run it again and let it sit overnight.
SteveSr
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The problem isn't usually residue. It is usually sawdust and small wood chips that make it through the coarse screen in the tank to the pump and get trapped in there while the piston keeps trying to flatten it in the end of the bore.
This is why it is hard to flush externally without disassembly. The piston keeps hammering the debris down while the rotary valve prevents a solid flow to flush out the debris.
Success!! I removed the pump completely, the outlet hose wasn't too bad to remove with it hot from using the saw for the last half hour. I put some air on the outlet (very little pressure) then turned the worm gear with my finger. I didn't see any actual crud come out, just a few spits of oil but after reassembly it seems to be flowing the normal amount again. From comment above this may not last & I will try to locate a new pump but doesn't seem available anywhere without converting everything to the adjustable one. Thanks all for your assistance.
Every season dump out the bar oil, pour fresh diesel/kerosene or mineral spirits into the rez put the cap on then shake it for 30 seconds. dump this into a cup and watch it for particulates, stop when it comes out clean. The in tank pickup will get clogged from sawdust and cellulose that can not be seen, removing the pump allows the hose with pickup to be easily removed and cleaned. Seems the non adjustable pumps often output more oil than the standard adjustable version. I almost always need to modify the adjustable pumps on stihls to use 80+% of the oil per tank of fuel.
thenne1713
ArboristSite Guru
It is also possible tank cleanliness not maintained and OIL tank screen clogged by wood chips? There was one old saw that MFR even had to change the screen bc chips were clogging entire hose all the way to the pump. I keep a paintbrush in pocket and clear/ clean caps area b4 and during cap removal to keep chips out of tanks.
