Bought this bike a week ago and the clutch was great then all of a sudden it started slipping

The guy had the adjuster nut on the lever as tight as possible there was zero free play. So I replaced the clutch cable and removed the adjuster nut at the lever to have free play clutch still slips

Adjusted the lower clutch also

It only has 12k on it

 

What kind of oil is in it?

You may need to replace the clutch....

 

I don't know

Is this a good clutch kit
http://www.amazon.com/gp/aw/d/B000GR...=AY6B10HJNSJYH

Also I think it may be cable related

 

Also I the owner the cable very tight

There was no room to loosen it

 

The cable only releases the clutch so you can shift. To loose and you won't be able to change gears, too tight and it is constantly half released and will feel like its slipping.

Slipping clutches are caused by the cable being tight, worn/damaged clutch parts, and prolonged use of incorrect motor oil.

The cable primary adjustment is on the lever at the motor. Get that close, then fine tune it at the bars.