These are found in go carts and scooters with 10 and 12 and 16 inch wheels
If you have a belt size of 743 20 30 this is a short case engine. If you have a belt lenght of 842 20 30 tis is a long case, the scooters with 16 inch wheels and some have 14 inch this is the GY6B engine. this is your engine