DIRECT GUARANTEED FIT FOR THE TWISTER HAMMERHEAD 150cc Buggy with WITH INTERNAL REVERSE ENGINE.  Comes with a one year warranty--see details.  This is a guaranteed direct fit for your vehicle and everything bolts up identical to your original stock engine including the shifting controls. You Can Also Get a Higher Horsepower Engine for Your Buggy--Guaranteed Direct Fit--See Options BelowADD A UNI-FILTER TO YOUR ORDER AND GET A ONE YEAR WARRANTY. YOU HAVE ADDITIONAL ENGINE OPTIONS Engine 1: 150cc stock engine.  Engine 2: - 170cc GY6 Performance Engine with Internal Reverse --GUARANTEED DIRECT FIT.  Click here for details.  Engine 3: 175cc GY6 Performance Engine with Internal Reverse--GUARANTEED DIRECT FIT.  Click here for details.Engine 3: 184cc GY6 Performance Engine with Internal Reverse. This is a different GY6 engine and you will need to purchase a adapter kit. If you are spending this much money we strongly recommend the 232cc GY6 engine.  It is a far more robust and heavy duty engine.Engine 4: 232cc GY6 PowerBlaster Engine:  Direct bolt-on engine with the purchase of adapter kit.  Click here for details YOU HAVE FIVE POWER PERFORMANCE OPTIONSOption 1: American made high performance Uni-Filter air filter ensures clean air to your engine and long life.  See why a NEW Uni-Filter is MANDATORY for ALL new engines and purchase at this link.   Your one year new engine warranty applies only if a new uni-filter is purchased with this engine.  If you don't get a Uni-Filter you are guaranteed to be putting dirt into your clean NEW engine.  See DetailsOption 2:  BDX High Performance Racing Transmission and Gates Powerlink Belt:  Click here to see detail or add to your order..  If you add this option the parts will installed into your new engine. A Performance Transmission is the difference between a sluggish, slow and inefficient go-kart and a peppy, speedy and powerful go-kart that utilizes the full power of the engine.  See details.  Regular price $249 - Now $99 with the purchase of this engine.  Option 3: The BDX A12 Cam Shaft changes the power profile of your GY6 engine  to provide the optimal balance for both low end grunt and top end speed.  If you purchase the A12 Cam Shaft it will be installed and tested in your new engine.Option 4: 11 Pole Stator, rectifier and harness adapter.  With this option you get more power to run your lights and other accessories.  If you get this option it will be installed and tested in your engine--Click Here.  The engine comes stock with an 8 pole stator.  Option 5: Performance Exhaust:  You can get the BDX performance exhaust for any of the engines above for an estimated 10% to 15% increase in raw power--see video!.  Your stock exhaust is restricting your power because the exhaust gases are being squeezed out through a tiny hole.  The BDX Performance Exhaust fixes that.  If you get a performance engine without the performance exhaust you will be restricting some of that NEW power. To see details or add the exhaust to your order click here.  Or see our video to see what this increased horsepower looks like in a race click here..Read article on how displacement relates to more power.How big bore kits & strokers workTAKE A LOOK AT THIS COMPARISONStock GY6 Engine BDX Performance Racing Engine We build and test our 175cc racing engine in our facility in Virginia.  We disassemble your 150cc engine, bore the case to make it larger so that we can install a 62mm big bore piston and cylinder.  Then we re-assemble and test your engine.Boring the Case for the 62mm Cylinder and Piston62mm 175cc Big Bore KitBe sure to read the article on how displacement affects your power.Click here to see additional important information regarding this engine.Visit our Facebook Group and share your experience and show some pictures and videos of your vehicle.Visit our Facebook Page and see the latest things that we are doing.