The chain and bar on my Stihl MS170 chainsaw was dry as a bone. There was plenty of bar oil in the tank but none was being fed to the bar and chain. Just before I realized what was going on I was getting smoke while sawing down trees. Right then the chain locked solid on the bar.
I removed the bar and chain and cleaned out the holes and areas where the oil should be coming from. That didn't work - no oil output even with the chain and bar removed and the engine running.
I left the chainsaw with a small engine repair outfit and after working on it for some time the technician said he had no luck either and he also checked with the dealer who said I will probably need the oil pump replaced or repaired and he said a special tool is needed to do that - repair costs likely over $100!
I had a brochure on hand with a special deal on the same chainsaw - but before rushing out to get a new one I decided to take a crack at fixing the saw myself. The method I used worked and the video and steps below show how I got the oil flowing again.
Step 1: The Video Gives a Good Overview of the Process
Step 2: Removing the Chain and Bar, Cleaning and Vacuuming the Mounting Area
A wood screw came in handy to remove crud from gummed up holes (gummed with sawdust and bar oil). The screw should be a little smaller in diameter than the hole. Gently turn the screw clockwise as you advance it into the hole. Pull the screw out slowly complete with crud.
Poking other tools and sticks into a critical hole (such as the oil output port) might cause further blocking.
Once the holes are cleared with the screw(s) vacuum the entire area with the shop vac.
Step 3: Pressurizing the Oil Tank to Clear the Oiling System
- Unscrew the bar oil tank cap and completely remove the cap and the retaining clip.
Make sure there is some bar oil in the tank.
- Find an adapter for your shop vac that will make a reasonable seal with the bar oil input spout. I had an old Electrolux vacuum cleaner hose that happened to fit the shop vac hose on one end, and the input spout of the oil tank on the other end. But whatever you can find to make a reasonable seal will do. Duct tape might work ok for example. The connection need not be perfect (mine wasn't) but a reasonable amount of pressure must be developed in the tank for this to work.
- Before blowing into the tank turn the vacuum ON and blow any dust or dirt out of the vacuum hose(s) otherwise you could contaminate the oil that's in the tank and exasperate the problem.
- Before pressurizing the tank double check you have the hose connected to the output of the shop vac otherwise you will be sucking up bar oil from the tank and into the shop vac.
- Make a firm connection between the vacuum hose/connector and the oil tank input spout.
- Turn the shop vacuum ON while firmly holding the connector to the tank spout.
- Maintain the pressure connection for a reasonable time - I waited 30 plus seconds... but the time required will likely vary from case to case.
- Don't expect to see oil oozing from the bar/chain output port (I didn't see any until I started the engine up), but if you see oil that would be a good sign.
Step 4: Start the Engine Up and Check for Bar Oil Output
- Replace the oil tank cap
- Start the engine up in the usual way with the bar and chain still off
- Check to see if oil is oozing from the oil output port
- If no oil is visible after running the engine for a few seconds repeat the pressurizing procedure (I had to repeat it once).
- Once oil is flowing reinstall the bar and chain and run another oil test - this time hold the end of the bar near a sheet of cardboard to see if you get any oil splatter on the cardboard (with the engine running). I did this test but got very little spatter and figured that I might have a problem (other references indicated that this test can be a useful indicator of getting enough oil to the chain).
- If all is ok to this point it's time to do a real world test.
Step 5: Checking the Chainsaw Operation in the Woods
Even though I didn't get much oil splatter on the cardboard I went ahead and gave the saw a test by cutting down a bunch of small trees and branches. I kept at this for at least a half hour without any apparent problems.
A visual check right after sawing indicated that there was light oil/sawdust residue on the bar and that was a real good sign.
I later removed the bar/chain cover and found that there is plenty of oil being distributed as indicated in the photo in this step.
Bottom line - the procedure worked and I saved myself a couple of hundred bucks!