my grand kids were given this 49cc atv because it wont start I have had the carb off cleaned it and again wont start with out either turns over like maybe the valves need adjusted is this a possibility

 

Yes, if the engine has low compression, either due to bore scoring, wear, burnt valve, or clearances closed up it would be bad to start. Re-set the clearances at TDC on the compression stroke, and see if that does the trick.

 

could you tell me what the gap is for the valve adjustment is

 

No idea, but if you try 0.003" for both, compression should come back if valve clearance was the problem.

 

If you need to adjust your valves on a GY6 moped I recommend 0.004 for the top one (intake valve) and 0.005 for the bottom one (exhaust valve). But make sure to make the adjustments when your piston is in its top death center. This can be done by inspecting your flywheel and aligning the T letter to the lining mark and if so also check the camshaft lining. It should have two small holes that should be perpendicular to the cylinder head and also a bit hole on the camshaft that is facing outwards from the cylinder head. This way your cylinder should be in its top death center. Then you can adjust your valves. That is what I know. Hope it helps.