Chain will not oil

50:1 that's 2.6 ounces of 2-stroke oil (preferably with fuel stabilizer) to one gallon of gas. I recommend using 89 octane gasoline for all small engines. It has little or no ethanol in it, as opposed to the 10% typical in 87 or 86 octane fuel. This will prevent a lot of fuel issues, especially if you are not using the tool daily or at least weekly.

is the tin plate on the right way?(not blocking the hole)did you change the bar and the replacement blocking the oiling hole

Check the oil lines to make sure none of them are clogged and that the oil holes in the bar aren't clogged.

The 50/51 and 55 always had the same bar mount, the bar was part no. 508912164 for 15" 508912172 for 18" and 508912180 for the 20", the oil is not fed through the bar adjuster hole.

not sure if the 455 rancher is the exact same as my rancher but when the oil feed on my saw seems slow i remove the chain and bar and clean the chain grove. pay special attention to the end that is near the motor there are a couple of places that allow the oil to flow from the saw body to the chain groove and then subsequently to the chain

Check for plugged fuel filter, air cleaner, and muffler. Check the fuel lines for decay or other damage. Check the chain for proper oiling and not so tight that you can't turn it by hand. Hope this helps!

Remove the chain bar and check to see if the oil hole is plugged or may have debris in it, check ball may be stuck open....

check the hose that goes to the oilway if everything checks clear you may have a crack in your oil tank due to excessive vibration and weak molding.

If it is spitting oil out, then your chainsaw is working properly. When it stops spitting oil out, then you have a problem. However, on the bottom of that particular saw you will find a little hole with a picture of an oil can next to it. You can adjust the lubricant output via the screw located at the bottom of that hole but, keep one thing in mind; the harder the wood or working conditions your saw is being exposed to the more oil will be necesary to keep your saw running smoothly and your chain from prematurely dulling.

Also make sure that where the oil is pumped against the side of the bar that the oil port (little hole) that feeds oil into the bar's slot is clear. Mine would go through a tank of oil with each tank of gas, but the chain wasn't getting oiled until I cleaned out this little hole.