Just rode a ZX-6RR

[Duo Maxwell]

A friend of mine has a ZX-6RR and I changed his spark plugs and oil for him. He let me ride it (this is my first supersport ride other than a brief parking lot tour on a 2008 CBR1000) and I must say I wasn't all that impressed until the thing hit about 7000RPM and on.

It really doesn't have any torque before 6-7000RPM....my 89 Kat 600 with a stage 3 jet kit has tons more pull. Granted after that bike hits 7k it rips your face off all the way to its redline at 15k....but iunno...expected a little more.

I also didn't like the handling all that much. It is obviously a lot lighter but it feels like I'm sitting on top of the bike rather than in the bike like the katana...which makes leaning and turning awkward.

I suppose I just need to get used to the handling....and the power issue might be something wrong with the bike itself, not entirely sure as I don't really meddle with FI...all I can think of is the ECU is bad, the injector is stuck/dirty, or the oxygen sensor isn't sensing properly.

Anyway, my 2 cents...I'm not knocking anyone with the bike...it's a damn great bike....just saying I wasn't as overwhelmed by the power as I thought I'd be.

-Duo

[None2Slow]

Thats how the 600ss bikes are. They are not known for low end power. Once you wind them up, hold on tight.

[yngveny]

I had pretty much the exact same experience when I tried the ZX-6.
Very little pull in the low RPMs, but really kicks when you pass 7-8K.

I'm sure it is a really fun and sporty bike, but I will stick with my Kat

[delkampg]

I also didn't like the handling all that much. It is obviously a lot lighter but it feels like I'm sitting on top of the bike rather than in the bike like the katana...which makes leaning and turning awkward.

thats one of the things i liked yet was uncomfortable with when i rode my friends 01 f4i it was so tiny and felt like a toy beneath me but at the same time you could flick it any which way.

[The CyberPoet]

It really doesn't have any torque before 6-7000RPM....my 89 Kat 600 with a stage 3 jet kit has tons more pull. Granted after that bike hits 7k it rips your face off all the way to its redline at 15k....but iunno...expected a little more.

When motorcycle engineers design an engine, there's a number of different criteria they can design for -- lots of torque, lots of HP, smooth torque, early torque, etc. The ZX-6RR engine (like pretty much all the SS bikes) is optimized for horse power at pretty much the expense of everything else.

Given that the formula for horse power is:
HP = (torque x RPM) / 5252

And given that torque in general is virtually linear with displacement (it changes only very minorly by compression ratios)...

That means, given the formula above, the only way to make more horsepower is to either change the torque -- which would require a change in the effective displacement (by using a larger engine displacement, or by making it act like a larger engine via a turbo and/or supercharger) -- or by spinning the engine faster. Thus, with a 600cc cap on the engine-class size, their solution is to make the engine spin faster.

Now, once you have an engine design criteria that requires the engine to be able to spin as fast as possible (without tearing itself up), you need to design the intake and exhausts to be able to breath at these high RPM levels. That means very big valves in order to let the engine breath enough, and very large intakes & exhaust pathways to let that air move in & out with minimum restriction. And both of those, by definition, reduce low-end torque (the Honda 02-09 VFR try to get around that restriction by using VTech to shut down one of each pair of valves for each cylinder until the engine gets to somewhere around 7k; other manufacturers try other tricks, such as putting a valve in the exhaust to build more back-pressure at low-RPM's).

The final result: you've got a bike you've got to ring the bells off of to get any decent forward thrust -- the price of compromise for using track-inspired values for real-world use on the street -- in a world where typical speed limits put the bike below the torque peak in virtually any gear. And as a result, you've got guys whose thrills in riding often require them to ride illegally, at least in this country (works in Germany on the Autobahns).

and the power issue might be something wrong with the bike itself, not entirely sure as I don't really meddle with FI...all I can think of is the ECU is bad, the injector is stuck/dirty, or the oxygen sensor isn't sensing properly.

There's probably nothing wrong with the engine based on your description (unless you're feeling lots of vibration, in which case it probably needs a vacuum-sync procedure, which is just like a carb-sync procedure). It just isn't the engine for your tastes -- you'll be happier with a bike that hits a broad torque level early instead (Kat, Bandits, BMW twins, etc.).

Cheers
=-= The CyberPoet

[scottynoface]

You rode the RR...599cc...race homologation special, of course it had no power down low. Handles like a dream though, yes you are on top of it, it's a race bike. It was made ONLY for track riding. You can register it and drive it around, but there was no thought put into making the RR streetable, which is why it doesn't have much oomph in the lower revs, who stays there on a racetrack?

If you want power before 7k rpm, look at my sig.

[Duo Maxwell]

Thanks CP...you're posts are always very educative and I've learned a lot just by reading your posts.

I was thinking that my next bike is going to be an f4i or an sv650. Obviously the sv has tons of torque down low....but would the f4i be similar to the zx? Or is it tuned to have some pull at low RPMs?

I'm assuming these problems are solved by liter-bikes...but I don't really have the money for one, nor the money for the insurance. It'd also be a little large for me at this point (been riding for 5-6 months or so). I just don't want to end up like one friend of mine (bought a ZX-6R for first bike, couldn't keep up with experienced riders who had liter bikes....so he bought a zx-10r 2 weeks later...goes without saying he still can't keep up, he's actually worse). That CBR1000 sure is purty tho.

I'll always be keeping the Kat...I love the damn thing. Tons of usable power, more comfortable then even my cruiser, amazing exhaust note (a little high, but with a low-end grunt), and pretty nice looks.

My cruiser I might keep I might sell, it's a GS450...a precursor to the gixxer engines, and it's a little similar...with a kick after 6k. It still has usable power below though.

God I feel like a bike collector. Have a katana, just bought the gs450 a week ago, and I'm already looking for another bike to add to the stable.

-Duo

[The CyberPoet]

Thanks CP...you're posts are always very educative and I've learned a lot just by reading your posts.

Your welcome. I pride myself on not just giving answers but making people understand the answers in a way that they can use the information in the future

I was thinking that my next bike is going to be...

First, let's look at what you want to accomplish....
You stated that you didn't like the super-high-RPM-to-get-any-umph of the ZX6RR. That indicates you want a bike with more emphasis on low- and mid-range torque.

Now, given that parameter, let's look at what will help fulfill that desire:

- The longer the stroke of the cylinder, the longer the torque event (i.e. - the longer the actual "bang" of detonation pushes the rear wheel forward). Generally, also the longer the stroke, the lower the total RPM ceiling is on the engine, because there is a limit to how fast a piston can travel & reverse direction without tearing itself up. This means long-stroke engines generally will produce power lower down than short-stroke engines, by definition.

- The larger the displacement, the more total torque produced.

- Single cylinder engines generally produce the most torque for a volume (single bang netting everything), but have the disadvantage of normally being very vibration-prone due to the fact that there's no inherent balance between cylinders (you've only got one). If you were going for a stunt bike or a short-distance city-carver, this is an excellent choice because it's torque-rich, narrow and simple.

- VTwins tend to produce more power in the low to mid-range than four-cylinder engines, because of their designs (dealing with piston speeds again), and have reduced the vibes heavily compared to a single. A long-stroke twin sounds like it might be just the ticket of what you're asking for.

- Parallel Twins give you the same basic advantages as V-twins (can be engineered with long strokes and easily have balancers engineered in), plus the front-to-rear engine length decreases quite a bit (smaller packaging). This makes them ideal for urban combat in longer stretches than a single would be comfortable for, and normally give you a lever-advantage at the bars over a v-twin because the bars can be closer. Choices include Ninja 250, Ninja 500, BMW F800-series, some of the BMW F650 series.

- Opposed Twins: Rotating the cylinders out of parallel and to the horizontal gives you the ever famous BMW opposed twins that have been popular for almost 80 years now... Since both pistons reach top-dead-center at the same time, balance is actually handled, but since the piston rods point in different directions (because the crank has to rotation, one is hooked at the top, the other at the bottom in this position), they do get a kind of harmonic unique to that engine design. One of the most torque-rich monsters on the planet for it's displacement.

- When it comes to four cylinders, there's a big advantage in vibration control (primary and secondary balance), and as long as the engine was build specifically for real-world street use (optimized for good low- to mid-range torque) instead of specifically for racing-class use (which are optimized to max HP), you'll be very happy. The best bang-for-the-buck in this class is currently the Bandit 1250's, which produce an amazingly useful amount of torque (over 75 ft-lbs of torque from 2500 to 7k RPM, then dropping off slowly). The three-times-as-expensive K1200 series from BMW is another one of these torque-emphasized designs, again coming in early with the torque and having an almost flat torque curve across virtually the whole RPM range.

-----

So, out of your choices listed, the SV would be the better choice for low- to mid-range torque, having both the advantages of a V-twin in terms of how torque builds, AND having more displacement.

But I think you would be well served to look into a larger-displacement Bandit (1100, 1200, 1250), the older ZX-12, an older BMW opposed twin (worth grabbing a ride on -- BMW dealers do free test rides by contract), among others, given your stated preferences in riding position (ergo's) and torque-building characteristics. Oh, and I'd be surprised if you told me that the insurance for a Bandit 1200 was significantly more than it would be for an F4i...

Cheers
=-= The CyberPoet