Check the listing for details. SSP-G (61mm BORE) 172cc DROP IN CYLINDER KIT FOR GY6 *NO BORING NEEDED*. Condition: New. Listed at 141.25 USD. 61MM ALUMINUM DROP IN CYLINDER KIT FOR 125CC AND 150CC GY6 ENGINES, COMMONLY REFERRED TO AS A 171CC KIT. IN MOST CASES, NO SPECIAL TOOLS ARE NEEDED FOR THE JOB AND NO ENGINE CASE MACHINING IS REQUIRED! OLD STYLE GY6 ENGINES MAY STILL REQUIRE CASE MACHINING, PLEASE SEE SPECIFICATIONS TAB. INCLUDES A LIGHT WEIGHT 3.6 OUNCE MACHINED PISTON. WHEN USED WITH A 57.8MM STOCK STROKE CRANKSHAFT YOU GET AN HONEST 168.9CC DISPLACEMENT. IT IS RECOMMENDED TO PAIR THIS KIT WITH A 61MM HEAD AND UPJET YOUR STOCK CARB OR UPGRADE TO A LARGER CARB. THIS CYLINDER IS .5MM SHORTER THAN STANDARD GY6 CYLINDERS. A SECOND BASE GASKET OR SPACER MAY BE NECESSARY IF THERE IS TOO MUCH SLACK IN THE CAM CHAIN. CYLINDER BORE: 61mmCYLINDER SKIRT OUTER DIAMETER: 62.8mmCYLINDER HEIGHT: 68.5mmPISTON HEIGHT: 31mmPISTON WEIGHT: 3.6 OUNCESMADE IN TAIWANPLEASE NOTE: NOT FOR USE WITH A STROKER CRANK! THIS IS FOR A BLOCK GY6 *54mm SPACING*DROP IN FOR SCOOTER MOTORS, IF YOU OWN A GO KART OR ATV YOU MAY NEED TO BORE THE CASE