Don Butler Custom Built 66cc SkyHawk ES engine

Grubee Inc


DB Custom Gt5A-ES engine.

Introducing you to the notoriously world-famous Roy Don Butler who owns and operates Don's Speed Shop dba: Pedals to Power in Chickasha OK.    Don is a full-time engine builder that takes our 66cc Gt5A-ES engine to the next plateau of performance.   

Here's what he does.

  • Completely disassembles a stock SkyHawk Gt5A-ES engine.

  • Drills more holes in the crank fly wheels to match the counterbalance weight of the piston, pin and connecting rod resulting in less engine vibration. 

  • Does a custom porting job on the cylinder 

  • Installs a windowed 47mm piston.

  • Installs a Super Clutch by removing the stock SkyHawk clutch shaft spring and then installs a 3 spring heavy duty clutch plate which prevents a slipping clutch due to higher achieved torque and horsepower.  

  • Installs a G2 Reed Valve assembly for piston port induction.  

  • Installs a high quality Oko 21mm dia. slide valve carburetor which is much bigger and more expensive than the NT 14.95mm dia. slide valve found with stock China doll 66cc engines.  

  • Installs a high compression CNC head with a thin copper head gasket. 

  • Bench runs a brief live test with a dedicated carb to confirm all is ready to go "Hot" for lock and load!

  • The engine is shipped with a untuned CARB DUE TO NOT BEING ABLE TO SHIP A CARB THAT HAS HAD GAS IN IT.   

  • Don includes an assortment of jets so the end user can tune as required for the conditions in their locality.   

  • This engine is not a fuel saving get around town on a dime engine.   It's made to turn enthusiasm into fear! 

  • Don says 40 to 50 mph has been documented with this engine properly tuned with expansion chamber exhaust and ran with the right ratio rear sprocket on flat land when ridden by a well-trained Chimpanzee.  Ha-ha! Just kidding about the Chimp rider!

  • The SkyHawk OCDT cordless drill start feature is appreciated when starting this hopped-up engine without having to pedal start.   

  • OCDT ( Over-Running Clutch Drive Tool ) is not included, must order separately. 

  • When you order this engine, it is dropped shipped direct from Don's Speed shop to you.   

  • We provide you with the contact email and phone # so you can deal directly with Don on any issues of importance or warranty.