Hi Paul, it certainly does increase the top speed in that you can actually reach it
I fully understand that it's a bit of a conundrum, in theory the smaller sprocket will decrease top speed. This is true. But, what is also true is that the bike's 6th gear is far too over-driven. This would be OK if if the bike had more power. If it did, then it could still reach top speed in 6th with stock gearing it would just be a bit slow getting there. The problem is, it doesn't. 6th gear on the stock bike is useless unless you are going down a long hill. Other then that, it's a power-sucking pit that you want to avoid at all costs
But in actual fact, the Performance Pack will
increase your top speed because you will actually be able to reach it and make use of 6th gear. It's ideal on the freeway. When I was only running the Performance Pack I was always pushing traffic out of the left lane between Parksville and Nanaimo. It's actually perfect because every once in a while, on a really good run, you get to bounce off the rev limiter in 6th. I recently got pegged at 120 on the Nanoose flats with the Performance Pack (90 zone) and there was a fair amount left....That cost me $175....and a warning that any faster and the bike would be impounded on a third tier charge...
Now if you live at the top of a 20,000 foot mountain and every day you go into town which is at sea level, then the gearing will actually reduce your top speed but that's not the world we live in (unless you're really a sherpa
).
Don't forget, there's a lot more to it then just the sprocket. The revamped ignition makes a big difference as does the clutch springs. The Performance Pack components are designed to work together as a unit. The revised gearing increases your RPM. This means the ignition has to work harder and so it gets a revision at the same time. The revised gearing also makes it a bit harder on the soggy stock clutch and so that gets a facelift in the process with re-designed springs. (that should be done regardless, this bike has the weakest OE clutch of any bike ever made - it slips and it slips right from the factory).
Then there's the fact that you're replacing marginal OE components with high-end stuff. You'll never need to a do a tune up and the chances are you'll never wear out the clutch springs so you can forget changing either of those again. For some folks, the idea of pulling the front wheel up a bit on power shifts into 2nd and 3rd is fun too. This is a side benefit of the clutch not slipping. So there's a lot more to it then just the gearing - it's improving all the weak links in the bike in one shot
Btw, don't write off acceleration rate too quickly either. When you decrease the zero to top speed by ~5 seconds it's a really, really big deal and it plays a HUGE role in passing cars. As far as I'm concerned, the stock bike is not suitable to safely pass cars at all. That increased acceleration rate will keep you from being left hanging out in the left lane next to the car your passing because you just don't have enough acceleration rate to get by him and have to wait until he lifts up on the gas to let you by (feels sorry for you). The Performance Pack pretty much fixes all of that
Acceleration rate is also really important when it comes to handling and cornering.
How about hill climbing? Nanoose hill on the stock bike was 80 KPH in the right lane tucked in. I used to have people passing me in the left lane slow down right next to me and you'd see the whole fam dambly staring out the window at me wondering what the little cute bike was all about that just couldn't make it up the hill. On the 'Pack, Nanoose hill at 110 in the fast lane is the low side of normal. 120 in 6th is a treat but this requires traffic to be just right.
So, there's a lot more to it then just a sprocket. The revamped gearing helps keep the bike in it's power band. On a stock bike, if you change into 6th, you will be below your power band in 99.99% of the cases and the bike just does not have enough power to pull it out of the hole it's fallen into. With the revamped gearing though, it tends to be kept 'on the cam' and this means it can (usually) pull itself up by it's bootstraps
Lastly, at ~10,000 k your getting close to wanting to look at the dampers in your rear wheel (the cush drive). They do wear out, they are included with the 'Pack and they will make the drivetrain a lot tighter (new bike feel). Typically, you want to look at them between 10k and 15k depending on how you ride etc.
People all over the world are running the 'Pack. I've got two Israeli's on them and one Palestinian living in Israel. There's a fellow up in Northern Norway with an '04 that's running the Performance Pack and retrofitted our Carbon Fiber Clutch kit to the bike (this can be done to the pre '06 models). There's somewhere around 30 people in England running the 'Pack and several of them on the Carbon Fiber Clutch Kit as well. Every weekend in Australia hundreds of CBR 125's get raced on 4 or 5 different tracks (Bucket Racing) and many of them are on the 'Pack. The weirdest place I've ever sent the 'Pack was to Humpty Doo (a town down under). There's at least as many in service in Canada as there are in the UK. A fellow in Scotland is running it on his carbureted bike. There's a few people in France running the 'Pack and also one brave sole in Lativa along with someone in Tartumaa, Estonia. Belgium? You bet. I haven't got a Russian on one yet but it's probably winter over there
Oh, and two Americans, one of which has the CBR 150 RR. How he got that over there is beyond me but good on 'em - that's a rare bike seeing that they didn't even get the 125
There's been a lot of great testimonies about the 'Pack but one of the best came from a racer in Australia. He bought just the springs and installed them between races. It didn't dawn on him (fully) that his clutch would now lock up and not slip as it had been. So he goes out to the starting grid and revs his bike way up there (as normal) and waits for the lights to change. As soon as they did he dumped the clutch and....pulled a giant catwalk in the starting grid
You can imagine the looks he was getting from the 20 or so riders in close proximity to him...he got the hole shot and finished the day on the podium in second place. As I recall he aced the next season taking top slot. Point being, his clutch, which used to slip and give him a cushion, now actually locked up and he hadn't taken that into consideration. He needed to alter his launching method