Are these swingarms legal in vintage racing? sounds like from what I've read online, the stock RD swingers are a bit weak and flex too much. by the sounds of this VRRA rule, it needs to be of "original style". but the last sentence "Replicas of period swingarms are permitted" and that swingarm on Oilypipes website is a DG replica from the times.
http://www.oilypipes.com/yamaha-products.html
http://www.oilypipes.com/yamaha-products.html