Quote from: Toydoc on November 10, 2012, 05:12:00 am

I'm with you. But how do we know if either one is "right on" with jetting, and what was the target jetting for (drag, trail, dune)?

I'd have to say that it would only take one or two sizes to be "right on" with jetting if it's at all out of tune.
It surely doesn't account for the difference between a 500 and 620 main jet.
Try putting a 620 main jet in a carb that was tuned for a 500 main jet and it'll be ridiculously rich, regardless of what type of riding you're intending to do.

Not always true. Every needle jet has a flow limit. I've had some with no flow change in MJ after 480. So could you add more needle jet to the 38 and bring it down to the 500? They are all combos that work, but is it the only one that works, and is it the best or right on? I really don't know so I'm asking.