An alternative to GY6 swapping a Honda Ruckus is doing a big bore kit on the stock Ruckus motor. Though very hard to obtain parts unless you know the right people, there have been 1 or 2 kits that have popped up over the years. Be warned, a Honda Ruckus Big Bore is a very DIY mod and will require modification to your cylinder head and associated parts.
What are the benefits to big boring a Stock Ruckus GET motor as opposed to just swapping it out for a 150cc? For one, you retain all of the bulletproof mechanics of the Ruckus motor (water-cooled, magnetic starter, magnetic water pump, simple valve train, etc) that makes the GET motor so reliable and efficient. From a legal standpoint, it would still technically be marked as a 50cc motor. This may prove beneficial to some places where there are more strictly laws on engine displacement sizes and emissions testing that would classify a 150cc swapped Ruckus as a motorcycle and cause increased insurance, licensing, etc.
So how do you do it and what do you need. Well first, you need to get your hands on a Honda Ruckus Big Bore Kit....No it is not one of those $50 kits you see on eBay, it is an oversized piston and associated parts made specifically to fit the Honda Ruckus. The 58.1cc Piston Kit has since been discounted, so there is very very limited supply and availability, so good luck getting your hands on one! The piston kit only includes the oversized piston, wrist pin, clips, head gasket, and piston rings. The part that requires the work is sending your disassembled cylinder head away to get bored to fit the oversized piston. This is the part that requires specialized equipment and measuring tools to properly bore out the Honda Ruckus cylinder head. Because of this, it is not simply a bolt on kit. If time and work is put in to correctly install and build a Honda Ruckus Big Bore, it will pay itself back in terms of acceleration, top speed, and longevity.
Here is a photo of the Honda Ruckuc 58.1cc Piston Kit:
Once you get your hands on a Honda Ruckus Big Bore kit. You will need to completely disassemble your Honda Ruckus GET motor. It will be handy to get yourself a shop repair manual for the Honda Ruckus if you are unfamiliar with the layout and inter-workings of the motor. This will also be a good time to replace all seals and gaskets. It is always good to rebuild with fresh parts, oil leaks are your biggest nightmare and can cause damage to the motor and what better way to prevent this than will new sealing components. We also opted to get a brand new stock crankshaft to aid in longevity of the motor. We didn't want to be breaking down this motor every month for repair so, now is the time to spend the time and money in rebuilding the motor properly. When you have your bare cylinder head apart, it is time to find someone who can do the bore work. A machine shop should have all the necessary equipment but we recommend U.S. Chrome for engine bore work. The stock Ruckus bore size is 37.8mm, we bored our cylinder to 41mm for the 58.1cc kit. You will need to send the new piston with your cylinder head so the machinist can accurately measure in there conditions and have the work done to spec. Once you get your bored cylinder and piston back, It is time to assemble!
Some other things to consider before installing your big bore kit:
Deck the cylinder head: This is when a tiny bit of material is machined off of the cylinder head surface to ensure a flat and level cylinder sealing surface.
Use ARP head bolts: High strength race grade head bolts that prevent lifting of the cylinder head and prevents the likelihood of blowing a head gasket.
Porting Cylinder head: Porting and polishing of the cylinder head should be done before reinstalling. The benefit of this is increased flow and performance for the bigger piston.
Here is a short tutorial on installing a Honda Ruckus Big Bore kit.
Honda Ruckus Big Bore Tips:
Use a torque wrench...you should always use a torque wrench when installing engine components. This ensures all head bolts are evenly torqued to ensure a proper and balanced cylinder head seal. Proper torquing of the head bolts can prevent blown head gaskets and poor performance.
Proper Break In: Properly break in your new rebuilt motor before you start testing the limits of the big bore kit. That mays going easy on the motor for at least the first 250-500 miles and changing the oil in between. This will allow time for the piston rings to properly seat and all components to wear in evenly.
Oil Consumption: Oil consumption can be expected on the big bore kit. But with proper installation and break in, it can be limited. Check your oil levels more frequently to ensure you don't run dry.
Retune your Ruck: With a bigger piston creating more power, you will also have to retune your Ruck to match. This means proper carburator, variator, and gear tuning to maximize the power potential of the new engine.