What would cause my 2001 dr-650 to leak oil at the top of the cylinder near the exhaust only when running? is it difficult to repair?

The engine in a 2004 JD Buck should be a Rotax 650, which is a 2 cylinder 4 stroke water cooled engine generating 62 hp. With that said, the most likely cause of oil in the air filter and leakage from the top of the motor is excess pressure in the crankcase. A cracked block is a possibility, but the most likely culprit is worn piston rings. A compression test should help narrow it down, but in either case you are looking at a complete tear-down of the engine.
https://www.rotax.com/en/products/rotax-powertrains/details/rotax-650.html

hey Joel, I think your talking about the little machined aluminum plug that blocks what used to be on the older 426 and 400 compression relief arm which is now internally built in to the exhaust cam.

Hi, This is likely to be your head gasket, white smoke from exhaust is oil being burnt. Oil is leaking from the gasket out to the external area that you can see, it will also be leaking inside to the cylinders causing the smoke.

Carefully check your intake manifold for leaks, cracks, separation. An air leak on the intake side between the carburetor and the cylinder head would be the cause of popping on the intake side. If there are leaks in the exhaust system, an o-ring seal in the head, or a seal between the head pipe and the muffler, this can cause popping or backfiring in the exhaust.

Hello,

The oil you are seeing may very well be from the bike sitting. I have worked on many bikes that have had similar problems. The oil bypasses the rings and gets forced out the top of the cylinder. Once the bike has been used for a couple of days, sometimes a few days longer, the rings expand sealing the cylinder and thus no more oil. It would be a good idea to examine the cylinder bolts too to make sure that the oil is not leaking from the cylinder head.

When a bike, or any motorized vehicle or tool, sits for an extended period of time, parts that are supposed to be lubricated by the motor running will dry out or shrink. This can cause a decrease in engine life and costly repairs. Always try to start your bike, even if you don't ride it, and let it run through the warm up procedure everyday.

Even if the oil leak stops on your bike, you should still have the exhaust leak fixed. Grab the exhaust pipe, when cool :o), and see if you can feel any slack by pulling on it. I would spray a penetrating oil on the bolts, let it sit overnight, and then try to tighten, or replace, them yourself.

Regards,

Oz

It very likely coming from the banjo bolt that retains the lube line that feeds the top of the engine. Remove the spark plug cover and check the tightness of the large bolt you will see. I have seen this problem a few times.

where does the tach cable fit? is it on or near the top of the engine so it runs of the camshaft , the is a very small rubber seal that could leak and look like a head gasket problem.

the battery terminal being loose would cause that, since the rectifier would freak out. the leak you speak of is probably not eh head gasket ro you would have compression problem with amount of oil that can run down the bike. It sounds like a corner on the valve cover gasket or something I think there is a cover for the valve adjust ment there so check it out the gasket may be worn. no biggie get a new one.
help this helps

Small oil leak at the top of motor