Engine Trouble Revs high for a bit

[agrmodz]

Hi, i am having trouble with my bike. Its one of them santa fe 66cc motor kits it has done well over 1000 miles. But it doesnt stay running when i pull the clutch in i got to keep giving it gas, and if i turn the idle up at all it seems like its going to be fine but when im going a decent speed and i pull the clutch in it revs real high and it slowly does down, also another way to make the revs die down faster is to le tthe clutch out again and pull it back in and let it go and pull it back in and it dies down.. how do i fix this? Thanks

 

[Street Ryderz]

Check for air leak at carb to intake seal or manifold to cylinder,also head and base gaskets.