Hi, I'm new to two strokes and need some advice. I purchased an older Yamaha street bike and the previous owner disconnected the automatic oil metering so I'll have to premix the oil and gas. The bike originally called for a 20 to 1 mixture. The bike is over 40 years old and with modern oils does this still apply and is synthetic oil a good idea. I understand some of the new synthetic two stroke oils claim they can be used at 100/1 on any bike. Any help appreciated. It's an early 70s street bike. Thanks.