Clutch problem

So I just fixed one of my boys with a kit... install went great... started riding it... it went great... then all of a sudden (after about a mile) the throttle isn't making the bike go faster... just makes it rev up.... come to a stop, and don't have the clutch in.... still running.... everything is mounted correctly... lever is functioning... you can see it moving the rod through the clutch sprocket (I don't know the lingo) and it still springs out. I don't know anything about the clutches... but everything seems just fine (i.e. lever, cable, clutch arm, etc.) but it is PERFORMING like the clutch handle is squeezed in (don't know if that is considered engaged or disengaged). Any input on this would be helpful... really don't want to buy another one just to fix this issue....

Thanks in advance guys

Don't want to waste another thread on myself.... Having another issue (different bike).... oil is coming from the end of the muffler.... the end is black.... i haven't seen this before.. is this somewhat normal?

As for the fuel... it was 16:1... I just told him to swap to 24:1.... it's a friend that lives across town, so i can't check it myself.... ill ask about the plug


As for the clutch.... that's just the thing... nothing seems amiss.... and it won't engage.... it's like it's stuck in neutral (we took our time before hitting the kill switch when it happened....Won't start now because it won't engage)