66/80 cc Motorized bicycle engine geometries explained

Well, I'll do my best to explain the three engine types currently available in the US. 40mm stroke PK-80 type, 38mm stroke GT-5 type and 38mm stroke "Half-breed" type. Although there is no consensus on the nomenclature for these engines, these terms are the best ones that I could come up with. If you shop in my store, these are the terms that I use for describing the three different engine geometry types. GT-5 type engines can be purchased from Rose 326a (ebay), Gasbike/Kingsmotorbikes or Piston Bikes. PK-80 engines can be purchased from DAX, Neil Senior (facebook) or Best Engine Kits. PK-80 motors with Z-L rods can be purchased from Bikeberry. Half Breed engines can be purchased from Piston Bikes (silver/black jet), Boy Goes Fast (ebay) or bestmotorkit (wide mount, 8mm stud). There are quite a few other vendors out there, but I'm not familiar with them. Optimal engines can be purchased from crmachine (piston port design) or Arrow Motorized Cycles (reed valve type).

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