Oil Coming From Exhaust

[lamptramp]

Just bought my first trials bike for 28 years and went for a 2002 315R. It seems to run fine but I noticed today that after running for a while, thickish black oil is seeping from the exhaust - both at the point that it exits the engine and also the seal of the rear muffler. Is this to be expected or does it point to any particular problem? The current fuel mix is 50:1 as that's what the previous owner preferred to use - not sure which oil he was using.

Thanks

[jfc]

If the bike has just been put putting around the oil will have built up, you have now got it hot and are seeing the result of years of unburnt oil. I do not know the recommended petrol oil ratio for your bike but it is quite a conservative ratio if the bike is not being ridden hard.

[tlrmark]

Montesa always recommended 80.1 for all years of Montesa 315 1997-2004. Your previous owner has made a mess of your exhaust system internally by running way too much oil in a modern water cooled bike. You will need to clean the exhaust out by disassembly. Always ran 80.1 in my 315 with no problems (nine years )

[thats_a_five]

For sure there is a large buildup of oil in your exhaust. I am not an expert on the 315 but you should be able to disassemble the system. You may need to drill out the rivets to get the end cap off the final silencer. Clean the metal parts with solvent and bottle brushes top remove as much gunk as possible. Throw away the oils soaked packing and replace with new packing and reassemble.

Be aware that when you restart the bike and get some heat into the exhaust it is likely to smoke while the left over oil burns off. You may want to do this away from neighbors. Best is to go find a long hill and ride up with a lot of throttle.

[lineaway]

Tlrmark is spot on with the advice. Usually I would say the burning smoke was good for the bike. This last summer I melted a mid-pipe from oil build up. Too many 5th gear wheelies at high elevation.