Question about 1993 Harley Davidson FLSTF Fat boy

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Oil coming from behind the primary case cover

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There are several places that the oil could be coming from. And, it could be either engine oil, primary lube, or transmission lube.

First, check for a leak at the cylinder base on the rear cylinder. I've seen that area leak badly enough to make it look like the primary is leaking.

The primary could be leaking from the seal that mainsaft runs through or the starter jackshaft seal.

The transmission could be leaking from the large final drive gear, or the front belt pulley could have become worn allowing the quad seal behind the pulley spacer to leak.

To repair these leaks is not difficult but you need a few special tools. Especially if your going to remove the front belt pulley. You need a device to hold the pulley while you put the 150 foot pounds of torque on it with the special socket you'll need for the nut. You'll also need a torque wrench that will torque in the reverse direction since the threads are left handed.

If you wish to tackle this job yourself, please repost and I'll give you step by step instructions but I would suggest you purchase a service manual for a job of this size and nature. A picture is sometimes worth a thousand words.

Good Luck

Posted on Sep 14, 2010


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The drain is a small pipe plug that uses a Torx bit to remove. It's on the underside of the primary cover back directly below the derby cover. You do fill the case through the derby cover opening. With the bike standing straight up, fill the primary with oil until it comes just up to the bottom of the clutch basket, the shiny aluminum drum that holds the clutch plates. It holds about a quart of oil. Do not overfill or the clutch will drag causing you to be unable to find neutral with the engine running.

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1 Answer

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