[RedCrowRides]

The Z190 swap will get you plenty of speed to run 70mph , main reason being the 190 has a 5 speed gearbox and the final drive gear is higher than the 4 speed final cog in the stock motor -


That said, get your 12" rims balanced at a good motorcycle shop, that should give you enough stability ,they do NOT come balanced from the factory and the 70mph zone will induce a "death wobble" on some bikes that just isnt an issue at the usual sub 50-55 mph speeds these bikes run at stock., due to the unbalanced rim situation.


Lots of scooters will run 70 and they have 12" tires so it can be done ,the thing is balancing the rim / tires which is done on those from the factory , you can indeed get a steering stabilizer set up cheap off Ebay , i run one on my Vader 125 , mostly just for looks, but it does actually function.