better picture

Bikeguyver, It could be a head gasket, but then agian, you say it after you let off the throttle you can gas it and it goes just as fast? You also might check your head bolts, & tighten them down. Make sure you check all bolts on the engine, I would also replace the muffler stud if it is brken off,, there might be some oil comming from there. If you are losing more power,,, chek going up hill,,, then check the head gasket & replace it also.. Hope this helps. Dirty

Head bolt /cap nut? Other threads reccomend changing the 4 cap nuts for regular shoulder nuts on the head ,,and re-torque to 12/14 ft pounds max in a cross pattern (search bar at the top of the page)The cap nuts may bottom out on the studs and not tighten allow ing the head gasket to blow out ,,,search for torque procedure star or cross pattern

Yeah- looks like the head gasket for the leak- if bolts are now tight- you'll have to pull off the head to see if it's broken-

the other problem sounds like typical carburetion problems and may not even be related-
I can't see the carb- likely the old stock carb designed for the 50 motor- the new 66 is available now for about 25- but I recommend the billet intake- which puts the carb closer to motor- I still haven't installed a 66 carb because the billet worked so well with the other carb-It's about $15 shipped from Pirates or Creative Engineering.

also a few more small holes drilled in the air cleaner seems to help air flow-

On second thought, after looking more closely- I'd say it is the muffler connection- I see the oil UNDER the muffler in the other picture

It's not really a bolt there- it's a stud- so if any of it is still extended- you may be able to unscrew it out- cut a notch for a screwdriver or a good pair of vice grips may work- if it's broken off inside, then you'll have to drill and use an easyout thing to unscrew it and replace.

I'm wondering about your motormount- it looks like a wider downtube- are the kits shipping with a wider mount these days, or have you modified it somehow?

Looks like a bad s-plug gasket to me. Keep an eye on the pluf see if it is bubbeling near the base.