Help diagnosing possible head gasket leak...

HT 66.... Runs good at speeds to 20mph...

As I increase above that the vibrations increase significantly (I have 500 miles on it and all this just started) and push it to wot the exhaust sounds like your taking the exhaust off while your increasing rpm's...

I have seen a light film of oil on the front of the engine but hard to see if its head gasket leak or just film of oil from small exhaust leak....

Can I take the head off and reuse the head gasket?? Or do I need to have a new one on hand before I check it out...

I may be interpreting the loud "exhaust sound" wrong????

I have cleaned it off and really see no signs of leak....

sometimes starting I feel a whoosh of air on my left leg but always thought it was air forced out of the carb....

At high rpm it gets real loud and clanky.....

I guess i'll just ride it in its comfort range and when is dies, bolt on a new one and fix this one.....

I dont see any obvious leaks...... With the clutch pulled in and revving it up in "neutral" at about 4000 rpm (guessing) you can see the whole motor start shaking... revving up more and it gets more violent.... Sounds like something has gone out of balance...

Wobbly wrist pin??? something else starting to fall apart???

It runs smooth up to about 21mph then as you increase the shaking gets real bad....

Thanks for your help....