Chain oil leaks can be due to several things.
Here are 7 things to check for when a Chainsaw seems to be leaking excess oil.
1.Have you overfilled your oil reservoir on your Chainsaw? Its very easy to do and amazing how something so simple and a tiny oversight can cause oil leaks. An overfilled reservoir can often leak oil when the saw is turned on. If this is the case, simply siphon some of the oil off if it looks excessively high. You can then power up the Chainsaw and see if the leak has subsided.
2.An over-oiled bar can also cause leakage. To prevent this, remove the chain and clean the bar with a dry cloth. Again, power up the Chainsaw and see if it subsides.
3.Check the fill plug is sealing the oil correctly. If this is not the case it could be leaking through the chain oiling line.
4.Clogged oil outlets around the clutch and sprocket can cause leaks if dust and saw dust has got into them. Simple maintenance of your machine can help with this. However, if they are clogged cleaning them out thoroughly can help with an oil leak. (Your manual will show where these outlets are)
5.Check your filler cap and see if there are any signs of wear or damage to the seal. If this is the case it is always best to replace this part to avoid any further leaks.
6.Check your pump gaskets for wear and wipe clean. If this part is dirty or clogged the leak may continue, if this part is damaged it is always best to replace this part.
7.If the oil is running out via the delivery line to the bar there is a chance the tank vent is clogged. If this is the case the chain may be running dry during operation. (refer to your manual for the placement of this part)
If you want to find out weather your chain is being oiled correctly, place a piece of card or paper on the ground. Point your Chainsaw down towards it being mindful not to touch the ground and just rev it once. If there is adequate oil on the chain a fine mist should spray from the guide bar and chain marking the card or paper.