NCY1100-1288 171cc Aluminum Big Bore Cylinder Kit for the Genuine 125 and 150 GY6 Scooters

This product was fine. Installed without a problem and had significant change in performance which was right away. No case mods or machining was needed. That being said, on to the bad part. The original cylinder wall/sleeve is about a 1/16 of an inch. About the thickness of a penny lets say. Well, when you get this product, and the case doesnt get any bigger, the space has to come from something. So, it comes out of the cylinder wall. This makes it about 1/3 the thickness of a penny. After about 6 months of weekday commute of 2.1 miles each way at pretty much top speed of 62MPH as much as possible (about 15 seconds or so each way). You will see in the picture what will happen. Mind you, I was not babying it at all. As fast as it could take me.. And I am over 200lbs. It reeally was not bad at all!! So, my advice to you is, if you wont be going full tilt all the time or just want it for occasional use and whatever.. THIS IS THE KIT FOR YOU!! It was super easy to do and I think that it was fine. However, if you want something solid and dependable, you WILL have to bore out your case. You can get a GY6 case boring tool on amazon right now for $159 and try to sell it to a local scooter shop when you are done, buy a case already bored out (Available online, google search), or take it to a local machine shop or maybe a place that works on motorcycles. They MIGHT do it. The tool is best option but will be needed! You cant really go over a 180CC kit or 63mm piston as the metal between the piston wall and the oil port would be microns thin as well as the metal that separates the area that houses the cam timing chain. NCY makes modified cases that have extra metal for that purpose but the case alone is like over $6-700.. Im sure its worth it but... not for me! Check out these pictures... They speak for themselves! Good luck! And stay safe!! (By the way, I originally saw I was burning oil so I thought maybe it was a ring problem. So I bought rings and yanked it all apart only to find what is in the pictures. Glad I did, it would have exploded inside the engine case probably!)

Had to cut the case

My scooter is so much faster now, i have to regear my final drive to take full advantage of the extra hp. In saying that when you buy this 2 things first buy a 61mm head and second you have to have an oil cooler the larger the better. Five minutes at full throttle and my scooter will start knocking do to overheating, a ncy works ok if you dont go full throttle for a long time what seems the best is to buy a larger radiator like one for a transmission as well a fan. Last they were right on increasing your main jet size what seems to work the best is a #125 giving im running a 32mm carb also you will need a larger slow jet still working on finding the best one.

So far so good installed it eazy again so far so good

A lot of power

Looks good quality but the cylinder is very thin wall so be careful installing and give it about 1500 miles before you go hot dogging it !

This product was purchased over the other big bore kits due to the high quality of the parts. Most big bore kits have cheapcast pistons that will require polishing to insure that the piston does not have any hot spots. This is a drop in kit without anycrankcase modifications. Best buy for the money period.

If you’re considering this upgrade: DONT! I installed this following all proper installation procedures and torque guidelines. After about 12 miles of use the cylinder wall broke, jammed the piston, and led to a broken rod. Now instead of a top-end rebuild, I have to split the case and do a total engine rebuild.