Big Boy Expansion chamber exhaust.

Grubee Inc


  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!