I don't know a lot, so I'm not going to waste your time, but here are a few pointers I have learned along the way that may help you.
this links rocks;
Speed Calculator For Go Karts and Mini Bikes
you need to figure your rpms...to do this find the KV(kilovolt) like the rating of hobby motors in rc stuff.
to do this take the rated rpm of the motor(2650rpm for 24v 250watt) divide that by the motor voltage(24v) you get a kv of 110 or so. Next multiply the kv by the voltage you intend to run....(36v) you get a rpm of roughly 3900rpm.
now your gearing and wheel size are the remaining factors in calculating speed. you won't be swapping tires, so it's the gears you're concerned about.
so for example you want a 44/13 and that gives you 20mph, but a 44/25 gives you 35mph....that's all fine and good, but it's going to take a lot of strain on the motor and a looooong stretch of road to get to that speed.
The key here is to gear for speed, but factor in load on the motor...electric motors are designed to run load free at top speed. the reason they are rated at 2650rpms is the max...they won't go any faster. They will also do what it takes to get to that speed. So the more load on the motor, the more heat. This is why you don't want to run straight amps to battery unless you are already moving pretty fast.
The next key is your controller, it is more like a gateway...limiting current from the batteries. so I really only focus on its amp rating. yours is 14amps so that means(in my experience) that you're popping the breaker going up hills and when the batteries are low. I'm surprised it doesn't trip just from sitting on it and hitting the throttle. Can it handle take off from a dead stop?!
My razor controllers are 30amp, and that is just fine for me. You can pick up a generic version for $20-$24. mine runs just fine on five 7ah batteries.
my 1st mod was a razor vespa style pocket mod. I removed the 250watt replaced it with a 1k watt 36v motor, 36v 30amp controller, 44t rear on 12in tires. The speed calc said 35mph on 48v. I ran it on 24v for awhile and it went around 15-18mph, but it took forever to pick up speed.(gearing) I ran it on 48v and got 26mph out of it. I bought a 60v controller (100amp) and added a 5th battery. I burned my motor up! black smoke, burnt copper smell! So I messed with the controller. I ran 48v on my MX650, it accelerated so fast it popped wheelies, it climbed hills! but again, smoke! and HEAT! So I ran 36v on my MX650...no smoke, no hill climb, just fast accel and lots of HEAT.
So I asked and asked what was the problem?! I was told that the 44t on 12in tires was too small...the motor couldn't spool up as fast as the controller was dumping amps into it. So my MX has 16in tires, but even the large 80t sprocket is too small. but they don't make larger sprockets! So I put it on my MX500 with TEN batteries! 2 parallel packs. Because I was told that larger capacity batteries were the 2nd key. I would only accel slowly, and I still burned it up.
So the controller is rated up to 100amps, but that doesn't mean it is throwing 100amps all the time, or even at all. But even if it's throwing 50-80amps that is apparently enough to burn up the motor.
High load(take off) and wide open throttle are the 2 situations where there is high amp action, this will 1.drain the battery quickly, and 2.burn up the motor. The motor is like a sponge, it will soak up all the amps it can from the battery, but if it cannot spin freely, that extra battery juice turns into heat. That heat radiates through the copper coils and to the outside of the motor case. So when you feel the motor is "hot" that energy is already passed through the motor. Now the copper wires have a coating on them to protect from heat, but when you overvolt, that heat is enough to burn the coating and damage the motor. So a controller with a high amp output will "dump" amps to the motor faster than they can be used.
The lesson I learned? the 30amp controller will let me hit 24mph on a 650watt motor just as well as the 100amp controller.
I acidently figured out I could run 60v on a 36v controller...I have a pile of dead controllers to prove it.
It is like running 36v 50amps I've been told, but I'm skeptical. the 50amps give you way more torque for quicker take off, but you could also gear to do that and not suffer the heat damage. I figure 36v is still only so much rpm. The low amp with high volts ensures high rpm which is more top speed. So your low amp controller is actually preserving your battery. I can't see how it is faster than a 30amp razor.
As I was saying about the batteries...you already know a larger amphour is just a way of saying more available power. I have run 4 12ah batteries on the same system as 4 7ah and my top speed was about 2-3mph faster. That should mean that the motor is actually getting more amps, but less than 30amp or my fuse would blow right?! I don't know about calculations, but if you look at lipo batteries for instance they have a 'C' rating for constant and burst rates...what this means is that they are able to run 25c constant or put out 25% of thier capacity on demand and 50c burst would be short term...like 3sec of top power under a dead stop. (this is all rough terms here) So again with the turbo button...what you are doing is going direct battery to motor...meaning there is no controller; no gateway. You can actually "shock" lower capacity batteries if the load is too great. Meaning the burst rate will be exceeeded and you will actually overdrain the sla battery and render it unable to hold a charge. See you can only use 20% of an sla's charge MAX before you have to recharge it. That's why the controller has a lvc(low voltage cutoff) this will slow down your scoot and even shut it down if you continue to use it. My old 24v razor could run until it barely crawled because there wasn't too much demand on the battery with a 24v system...that how they claim you can run for 40mins....the last 10minutes you're going 2mph! when you overvolt to 36, 48, 60v, you get about the same 20min run time for all of them, but the higher the volt, the quicker the cutoff. on 36v I could get home when I hit 'low' before I'd have to push it home. on 60v it runs just fine until it hits 'low' then it instantly cawls. If I'm too far from home, I'm not making it back. and that is voltage sag or the throttle demand on the battery. the throttle's saying more juice! the battery says I have a shelf life!
larger capacity battery lets you run a little longer, but not much in the long run because of all the extra weight.
so why not go lipo?! too expensive and prissy! I'd LOVE to, but you really have to baby those bad boys! especially if you're piecing hobby grade lipos together. You could essentially get 6s batts ...22.2v 5ah for $50each....4 of them would get you 44.4v 10ah for around $200, plus harness, charger, etc....$300tops would get you a very nice lipo set, but you really have to watch them when riding AND especially charging! Especially charging them all on the same charger. You're almost better off getting 4 chargers, but at $40 each that's not cheap. That's just too much money for me.
If I wanted to tweak my vehicle to perfection I'd get a 50amp controller(lb 37) 5 12ah batteries and a 48v 750watt motor. that should get me around 28mph on my MX650....right now it's running 60v on 7ah batteries and hit about 23-24mph....slow until I hit gravel then it's reallll squirelly! It's enough for a 10min laugh and a 3hr recharge. it is what it is and I've decided I've gone far enough.
hope this helps.