New member, new bike

You could certainly have a leaky valve cover gasket, but also check that tach cable. I rebuilt my tach pickup, which mostly a mounts to cleaning and reassembling with new o-rings.
Not saying you don't also have an exhaust leak, but easier for you to tell that than I.

 

That looks more like a leaky tachometer drive oil seal to me.

YOu can test for a leaky head gasket by cleaning off all the gunk, letting it dry, and dusting the area with talc. Start the bike and watch the area around the head gasket. If there is a leak you should see the talc puff out, or oil starting to stain the talc.

 

Would leaks in the tach drive oil seal or exhaust cause the bike to sputter in low gears and have reduced power?
I have the Haynes manual and I'm trying to diagnose the problem. I'm starting to think I need the professionals to take a look.

 

No, those kinds of leaks shouldn't do that. More likely fueling and/or ignition. Now that you've run it, check the plug colors. I don't recall if you did, but setting mixture and syncing the carbs is important to it running well. Once I did those things last summer, I spent 100s of hours riding without issues.

 

Vagabond, One of the first things I would do before starting to work on an older bike is a compression check. It can tell you a lot of things like if your head gasket is blown, your rings are good and if your valves are way out of adjustment. A compression gauge is not that expensive and they may even have one you can use at your local auto parts store. There are a lot of youtube videos showing how to do this. I would recommend watching Max Storey's videos. I have learned a lot from him. This link will take you to his video on doing a compression check.

 

Hey y'all. Thanks for all the help throughout my motorcycle journey. I hate to say it, but I'm going to sell my XJ. Hopefully one day I'll have a garage and be able to put in the work that a cool bike like this deserves.
Just wanted to tell you guys that I appreciate you and this forum was super helpful!

 

Yeah, sorry to hear it. These projects test your resolve. My project is also suffering a hiatus, but it is a logistical one since my workshop got shut down. Hope to pick it up again in the summer as my new workshop gets running.