Added to the horsepower of a 17% increase in displacement is the 7% increase in horspower with only adding an exhaust on a bone stock bike, for essentially a 24% increase in power.

This is not insignificant.



And add to that a 4% reduction in curb weight to just 292 pounds combined with a 135 pound rider, and performance starts to get lively.

 

The last thing a 250 needs is higher gearing, if 1st is too low, shift to second.
Post your maximum speed and rpm's, you are way over geared! It's probably faster in 5th!

 

These percentages sound great, but what's the actual output? Because that's what matters. You can add 7% horsepower, and that's great, that's better than stock obviously, but that doesn't mean you're making substantial output still, because we're starting with such low HP and TQ to begin with. If we increase the HP of a Toyota minivan by 7% then it still isn't a strong performer.

As far as "lively" performance, I suppose that's down to perspective. A motorcycle making what, 24 HP or so, is not typically considered lively. Compared to a 50cc scooter, sure, but when you look at the whole spectrum of motorcycles, or even just enduro bikes, it is objectively slow.

Note that I am not saying this just to argue to anything like that - I'm just saying let's be honest with ourselves here. It's ok to say that some of us are alright with having slow bikes, that's fine, but lively to most motorcycle riders means something different than it does to apparently most members of this forum. Same goes for a very tall geared KLX being a good cruiser.

Honest question for anybody that cares to answer: KLX aside, what's the fastest bike you've ever ridden?

 

OR, you running a new 300? If you tried it up a 3% grade, I would think 5th would be faster, maybe 4th. So if one get's to a hill, you'll need to downshift. I run a 13 counter with a 350, I really like it cause you can just inch it around on the single track.
....so from you info, you could just use the first 4 gears, the other 2 are just for cruising. I agree that this bike has a pretty flat power curve. If you put a hot cam in it you may have different results? ...maybe.

 

JMO, and I really don't care about your own preferences, so if you're happy with it then great. But for everybody else that's reading: if you can't pull to the rev limiter even in 4th gear, then the bike is geared way too tall.

Also JMO: being in 4th gear with those sprockets where you can't even pull across the whole tach at wide open throttle, yet in saying you can roll from 25 "right back up" to 40, means you have a very mellow expectation of what "right back up" means compared to most other motorcycle riders. That's not a problem (if you're cool with it then that's all that matters with your own particular bike). I'm just saying it because it ties to my next point, that:

These bikes do not have any low end power and under no circumstance do they "pull hard". I mean this sincerely when I say that anybody who thinks that these bikes pull hard owe it to themselves to go test ride something actually quick to gain broader perspective as a motorcycle rider. Go ride something with 100 horsepower for a little while and then get back on the KLX. It will feel like literally nothing is happening at all under wide open throttle. That's fine for what this bike is designed to do, like light trails and such, but saying that these bikes "pull hard" is very misleading to those who may be reading this for research purposes.

 

This is also why it goes against common sense to gear these bikes tall for cruising purposes. Having to downshift everytime the road becomes slightly inclined does not make for a more relaxed cruiser. For cruising you want to be able to set it and forget it in one gear. Gearing so tall that you're easily falling out of the powerband and having to work the gearbox more often than stock is the opposite of that.

When I went to a 13T front sprocket I loved how much more usable 6th gear actually became since the engine was turning at just a higher enough RPM to allow me to ride those inclines without downshifting into 5th anymore. And yeah, the cruising RPM is higher, but our bikes are buzzy either way. One option provides you a buzzy ride with a versatile top gear, while the other option provides you a buzzy ride with a significantly less versatile top gear. Personally, for my bike, it's no-brainer.

 

While I have lots of fun modifying my 300SM...
for me it is not just a toy because I use it daily for utility transportation in my business to carry my tools and take me to jobs. So I use my 300 to make money. By the time it comes to the end of its service life it will easily more than pay for itself.



I'm 74 years old, and been riding small underpowered transportation motorcycles for 57 years. They have all served me well for most of my life, as well as made me lots of money as useful tools.

I can tell you this. Riding today is just as much fun as when I first rode my new Yamaha 250 home from the dealer in July 1965.

 

When you can pick up 5-10% power for a hundred and a half or get more low to mid range for trail riding it's a pretty good deal. The 299cc AHL cylinder kit for under $200 is a pretty good buy. To get crisper quicker acceleration finding a Mikuni 36-68 can do a good job too. Least gain for the money spent is an exhaust.

Have you actually ridden a bike with a gain of around 5-10% before and after the modifications? I have and I can tell you that 27cc gain in my 650 would pull a stock 650 quite easily by bike lengths through the gears. It was a 27cc gain using a Kawasaki Vulcan 1500 piston. I've also ridden 100cc bikes then 125cc bikes and that is quite a gain in power too. Smaller the bike the more noticeable it can be.

Now you ask about bikes, CBR900RR, Z1 (1975), ZX6R, V-Max, CB900, CBX, and a few others. Didn't really run any of them to high speed, but did use some of the RPM. The ZX6 convinced me I didn't need that kind of speed. Oh and by the way Kawasaki used about a 36cc increase in displacement to put their ZX6R at the top of the 600cc class street bikes. They still build a ZX6RR that was actually 600cc for racing, but the street ain't racing and that 36cc made the bike that much stronger.

 

I have, and gains in a slow bike are certainly noticeable over stock, I agree. But in my experience that honeymoon phase wears off quickly and then you're still left with a slow bike. Just because it feels quicker than stock, when you're so slow to begin with, noticeable improvements don't mean it's enough.

I'm EFI for what it's worth. AHL kit price alone is deceiving because then you also need a fuel controller to support it and obviously its a smart idea to get a pipe too. The price balloons to $600+ very quickly which really ruins the value proposition.

The 37cc bump for the ZX6 was first implemented twenty model years ago now so believe me I'm aware of it. The current 636 also has I believe 134 horsepower. Little different then going from around 19 to 22 or some such in our case. That engine has such a better flowing head than we have, it can take advantage of the added displacement much better than our lethargic head and cam profile can. Engines are all about the symbiotic relationship between every component, not just throwing a small amount of displacement at everything and expecting mega results universally.

 

Seems people do care considering multiple people are conversing with me about it. No such thing as "your" thread here. Also note that I'm not the only one that disagrees with gearing these bikes taller in "your" thread, but you conveniently ignore them and single me out.