GOOFIT 50mm Big Bore Kit Prestazione aggiornamento Sostituzione per GY6 50cc 100cc 139QMB Corsa Scooter

Das Kit passt super, der Roller läuft wirklich gut. Danke GOOFIT

I bought this bore kit for my wife's 50cc as her scooter piston had gone and thought it would be a cheap up grade and was surprised with how much performance it gained on a stock engine it went from 30mph stock to 45mph gps speed with out any other mods and left my 50cc behind I was so impressed I bought a second one and fitted it to mine I'm running 6.5 roller weights and a performance variator and getting 55mph the only down side to this kit are the 9 gram rollers that are included are too heavy and a shame it does not come with 6 or 6.5 gram rollers but very satisfied

Wrong zize poston and cylinder

Cylindre et culasse en centimètres cubes très bien mais dommage pour moi il est trop gros pour mon scooter 139 QMB 50 cm

Very good product. Tip of the trade here. Kit comes with oilpump, same as original, if your oilpump works just set the oilpump aside and install only if needed. Did install an A9 cam with this kit. Recommend the cam. The head is small valve, did porting and valve shroud ( the valves sunk in a bore and the bore shrouding the breathing dremel out the shroud and dremel out the port. however AVOID ENLARGING THE CHANNELS, very little wall material on some spots.just try to takendown the big wart that is cast to hold the pressed in valve bushing.On a 50cc base engine this head will do the same as a big valve head, so keep the head and dont be dissapointed that its a small valve head.Engine displacement. You will get a bit over 80cc with the 50 mm bore.(Formula: Radius X Radius X Stroke X Pi (3.14)) or as with this kit 25 X 25 X 41.4 X 3.14 = 81.44....or 81.5cc. Its called 100 cc kit but everyone and his brother markets it that way.Carburetor, Do NOT buy a 24 mm carb, its overcarbed and you will have issues. An 18 or 19 is perfect you might get away with a 20. If you have a cheap sealed carb, toss it and get a carb you can adjust, and open up to change Jets. With this kit, you might want to start with a main jet around 80-83 somewhere. Watch Youtube, plenty of videos on how to install and tune. My scooter is now doing a bit over 60 mph and have a very good response and pick up. I do recommend you put in a 2000 rpm torque spring (the red one) with this kit. Run as high octane as you can get hold of because you will bump up the compression pretty significant with this kit. A word of warning, many buys a race CDI and have a hard time starting, and don't know why. Many of the race CDI don't retard the timing on very low RPM (as when youre starting), if you want to put a race CDI on your scooter, find one with advancing and retarding curve, otherwise you blame this kit, or get into a long carburetor fix, that doesnt fix anything. Stick to the stock CDI (stock CDI will retard at start) until you have found an advancing/retarding CDI. This kit comes with more gasket you will need. And the parts are well done. I would take my time to mirror polish the top of the piston, and the combustion chamber, careful not to damage the valve seat. The valve seat has a 3 angle valve cut already when it comes so nothing is needed with the valve seat. You can , and I recommend that, grind the valve and get a vitnessmark where the vakve will seat, and do a back cut on the valve up to and close to that mark. You can also make the circumference of the valve head , the edge..make ut round, and you will get a better flowing valve. If you have a steady hand, you can put a piece of protective leather around the valve stem and put the valve in a hand drill, and work the valves with a file.All in all, this kit rocks, and if you do all those little extras, you will beat all big valve heads.Im very happy with this kit and I strongly recommend it.You can just bolt it on and get a much faster scooter or do all the small tweaks and get a rocket.Word of warning...you will have a bigger engine, and thus you will have more heat. When putting on your cooling shroud, be very anal, it will pay out, go over small cracks and openings with black silicone.Good luck to you all