Why Is My 1979 Ducati GTS900 Leaking Oil from the Crank Case?

Technical Guide - Ask Brook

🔵 Why Is My 1979 Ducati GTS900 Leaking Oil from the Crank Case?

Category: Engine / Oil System / Diagnostics

Video & Written Response

Oil leaks on the Ducati GTS900 and similar bevel-drive twins are often misdiagnosed, especially when they appear around the bottom of the crankcases. One common but overlooked source is the screw that retains the oil drain screen insert. This area does not always have a perfect sealing face, and depending on assembly condition, it can become a known weak point where oil seeps out.

However, it’s important not to assume this is the only cause. Oil can travel and collect in ways that make the actual source difficult to identify. A proper diagnosis starts with thoroughly cleaning the engine using solvent or contact cleaner, ensuring the entire crankcase is free of oil residue. This should include the area from the alternator side through to the clutch cover, so any fresh leak can be accurately traced.

Once the engine is clean, the bike should be ridden again and inspected immediately after to identify the first point of oil emergence. In some cases, the leak may actually be coming from another common area such as the sprocket seal. Only once the true source is confirmed should any parts be replaced, allowing a more accurate and effective repair.

Watch the Video

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Original Question

Marc Di Leo

Hi I recently purchased a 1979 GTS900. I have receipts showing the bottom end was rebuilt at Vee Two approximately 15 yrs ago. I am very happy with the bike and it runs quite well for an old girl. However it does have an annoying oil leak coming from the bottom of the cases. My question is what do you think may have caused this?

Thanks in advance.