Big Boy Expansion chamber exhaust.
Gru-Bee designed this expansion chamber exhaust many years ago, now others in China have copied it. No intellectual property protection in China!
BIG BOY measures 12.5 inches overall from flange to exhaust tip
This is a YuanDong SkyHawk manufactured muffler. I was amazed at watching the ladies acetylene weld these on the shop barn floor.
On YD'S dyno a 66cc engine muffler did produced 10% MORE TOP END POWER.
Is it quiet? No, she's one loud puppy.
Will it fit all 2 stroke China bicycle engines? Yes it will.
Will it fit on all bikes, No it will not.
Get an idea what it will fit by looking at the pictures.
Big Boy Measures 12.5 inches over all; flange to exhaust tip.
Buy 2 at no additional shipping cost and sell one to a friend. Comes with exhaust gasket.
FYI: 2 stroke engines produce more power with an expansion chamber exhaust system. Very Loud! Not a quiet street muffler. Best for performance requirements like flat track or street racing! This is what you need to have the Bad Boy on the block image!