Gt5A-ES Don Butler Custom Modified

Grubee Inc


Here's a standard Gt5a-ES SkyHawk engine that has been given the Golden Midas touch of the world-famous Don Butler Speed Shop in Chickasha OK. 

This engine is Electric Drill Start compatible.  We expect to have the next shipment of OCDT by the end of January 2023. 

The improvements Don makes are not obvious from the outside.  When we get your order, we send Mr. Butler one of our SkyHawk Gt5A-ES engines and that only takes about 2 days. 


1.  When received, Don disassembles our engine and balances and aligns the crank assembly.  ( 5 balance holes instead of the stock 2.)  

2.  He Protractor indexes the piston travel to TDC and BDC and then Dremel grinds the cylinder transfer ports and exhaust ports to gain maximum engine efficiency.   

3.  Reinstalls and shim realigns the crankshaft.    Replaces any bearings not to spec. 

4.  Checks piston to cylinder slide fit. 

5.  Secures a piston squish of less than 1mm.   

6.  Checks clutch operation and adjust accordingly. 

7.  Installs his God-awful decal on the magneto cover.  

8.  Removes the OCDT flap over the OCDT hole.   Guess he wants to give lonely Mud Dobbers a home place.      We can ask him to reinstall the flap if you want.  

9.  We will send him a 7 pcs Shim kit and CDI Module to be include with his masterpiece engine.   At the rear he includes 2 long nuts to better hold engine to the bike's down tube. 

10. He ships the engine via USPS Priority Mail that he spent the whole day making into a sweet running China Doll just 4U.