Valve Clearance???

[Queensmate]

I Just fell off the turnip truck and am still bouncing my head off the ground trying to figure what the correct clearances are for my pit bike. I found this bike on Craigslist so I have no manuals etc. It is a 149cc vertical Loncin motor. The stamp on it starts with LC162FMJ. I have been trying to dial in the carb and the valves. Right now they are set at .003in and .004ex but I still hear dull tapping on rev or starting about 2-3rd gear. Also I got most the backfiring to stop and it idles but I have noticeably lost some power and speed. Can anyone help?

 

[zwebx]

i run on my lifan 150 .006in exhaust and inlet at .003in
i assume they are steel valves so i could imagine when they get hot they would need similar clearances... the problem you are having is the clearances are running are too tight and when the engine heats up the valve stretches and stays open, therefor reducing compression and making it ride like crap and backfire alot
tapping could be the valves touching the piston... they will probably be okay so try the larger clearances
never mind about tapping in most of these engines you cant stop that

 

[DHZ_XR8cing]

.004 on an exhaust valve is plenty. They will still have a slight rattle. Its when there is no rattle at all you will create problems.