I'll try this one more time, the max rpm rule is set and checked while the kart is on the stand, just because they are set at 5400 rpm on stand does not mean that's automatic what they race at, what they race at is dictated by the gearing on the kart and track size. If your tach is only reading 3300 rpm after the race, like Brian points out it's because your setting in your tach is off, you need to go in and reset that setting in your tach, which has nothing to do with adjusting max setting of the motor on the stand.
Back to your original question of what close gearing for 1/5 mile dirt oval with an out of the box predator, I can assure you it's not a 13/63 that's no where close, you only want to race that motor at 5000 max with a 13/63 your trying to turn it like 8000 rpm which of course it will not do, The only reason you won the race is everyone is way off on gearing as well.
The gearing I gave you in post #8 ( provided all your details are correct ) would be close, might be a little low on rear if track makes very little grip and tires and set up is off. easy way to test is leave your 63 on the rear and put a 16 driver on you should get a lot faster even though that gearing is still way off.
Do they race Sr Clones there ? If so do you know what the front runners are using for gearing ?
Which Tires are you on ? what air pressures ?
Thanks and God bless,