I don't have a YFZ450 but I do own a Raptor 660... When I bought my bike it had an Edelbrock on it and let me tell you, for the Raptor it sucked a$$!!! It surged top-end and just didn't have the fuel capabilities that the raptor needed. So I swiched back to the stock carbs, and boy what a difference. Both times it was tuned perfectly as I have the JET-4-POWER module. Everyone I have talked to says the edelbrocks suck, and it is true, Raptor wise. Go to
www.yfzcentral.com and post a topic there or just do a search im pretty sure you'll find your answer. For your application it might be worth it but for the raptor going from twin 33mm (66mm) carbs to a 48mm I think the edelbrock was it just didn't supply the fuel needed for my motor... I switched it back to stock with a Dynojet stage 2 jet kit installed and I couldn't be happier. When the bike had the edelbrock on it it ran far less smooth and took longer to warm-up... Ate more gas too???. I sold mine on ebay for $431.00 and never looked back....
