i just bought my husband a 1979 yamaha 1100xs. it now seems to have an oil leak but we can't tell where the oil is coming from, it only seems to leak when he is riding it, the first real ride he was able to take it on is when the leak appeared. he even found oil dripping out of the air filter compartment, so we replaced the air filter. and he had found a loose hose clamp which he thought was the problem. so he replaced that but today when he took it out again the same thing happened. He did say he left the gas tank on choke when he rode it, i don't know if that could cause a problem? if anyone has any suggestions please let me know.

Hmm, that's an old bike, so, not too sure i will be right, but, i think that the crank case may have a breather pipe that connects to the air filter, it is possible that this may be blocked, or, there is simply too much back pressure from the crank case forcing excess oil out, hope that helps

I dont know if this will work or not but a old fart told me he uses a white oven cleaner on the area of the leak. After a short ride he can see where the leak is starting from. Sounded good to me anyway.

Jerry