How does powerband work?

[classic zed]

When i started to work at scooter world they sent me down the road to get some power bands........ FUCKERS

reminds me of the time I was sent to the stores (2nd day of first job) to get a box of sparks for the grinder, the storeman asked "do you want blue or yellow sparks" I didnt know so I went back to ask, everyone was pissing themselves laughing, Bastards.

[Motu]

You guys are full of shit,stop pulling his leg - it's an old joke mate,and they all sucked you in!

Any good mechanic KNOWS that when you install new powerbands it is CRITICAL to lube them with elbow grease or they will not slip properley into place. And if THAT happens things get pinched badly. That reduces the power due to the non-egagement of the power band and the bike ends up with a super high exhaust pitch that sounds like Alvin the Chipmunk on steriods and caffine all at once but with no power at all.....

I've planted some in my garden this year,they are coming on nicely and shoud be ready by early feburary I reckon.I'll try them on my bike first,then let you know....I might sell some here,they'll be much cheaper than the dealers or even Mitre 10.

[SlowHand]

Hi

Between 1976 & 1982 all of my bikes were single cylinder
4 strokes. In 1982 I bought a CB750, my first experience of a
4 cylinder bike. I bought this bike due to it being on sale at
only $1000 more than the cost of updating my XL500 to the
latest model. The 750 initially felt quite sluggish in comparison
to the XL500 due to the fact I was only revving it to accelerate
by the same amount as my old XL. It took me about 6 months
to discover that it had a different powerband to my old XL as
I was never told by the dealer the different charactaristics
of the DOHC 4cyl in comparison to my XL500.

Good song that - who's it by again?

[Ivan]

What Ixion said, but if you have an RG150, don't get all excited and expect to drag off an R1 at the lights - their powerband is fun, but NOT QUITE as powerful as this explanation!

Hey Id argue bout that I have an RGV slower and less powerbandy to the RG and dragged of a V8 Falcon at the lights on my RGV and he was going flat tacker I held rev at 6G an when those lights changed green just gunned it throttle wide open I aint lost a light race yet

[roger_doger]

I may be missing the mark here but I think there may be a bit of confusion here stemming from what is correctly known as a powervalve. A powervalve is a sort of sliding plate that is attatched in front of the exhaust port of two stroke bikes (motocross and some road). The reason is that because high performance two strokes have large expansion chambers to produce high power, they would otherwise suffer greatly in low to mid rpm power because of the lack of exhaust back pressure. Different setups are operated either by cable or electronically. The "valve" is down at low rpm to create more backpressure (and power), and then opens at higher rpm so the bike can produce maximum horsepower.

The effect of all this is that in real riding conditions, it creates a sudden surge in power when the valve opens, which is a trademark of any high performance two stroke.

The confusing bit is that a powervalve is often called a powerband. But that word is also used when describing the power delivery of any motor.

But to be clear, powervalves are only present in the form described on two strokes. There is additional confusion to this saga however as Yamaha, and more recently Suzuki, have used the same principle in their four stroke sports bikes in the form of valve located in the middle of the exhaust system. This setup is used for the same purpose as a powervalve in two strokes

Just my 2c worth

[TwoSeven]

yes, a 4-stroke powervalve as in the zorst changes attenuation length and for different rev ranges. Suzuki's is rather interesting as they also use it to allow for a short fat megaphone.

[Skyryder]

And here's me thinking a power band is a Rock band pumping iron.

Rode a mates 350 Kawasaki a few years back. Just down right dangerouse. Those mothers had a lethal power band. The powere to weight ratio was from another planet. If memory serves me right more riders came to greif on the 350 Kawa than any other bike.

Skyryder

[TwoSeven]

If any of you want an example of this, look at a dyno for an 05 Triumph Speed Triple. It has the flattest motherbeast of a torque curve ever. And they say it is the best wheelie bike evar made.

This is a characteristic these days of fuel injected bikes with all that electrikery. The higher the value of the number is what gives it the ability to wheelie (its rate of acceleration) - the change in the number simply gives the bike a characterstic.

Torque curves on dyno charts are odd to read. Its actually telling you the acceleration characteristic of the bike at a given rpm and power (so you read it as a point - not a range of values). If its the same number all throughout the power range, then the curve will be flat and the bikes acceleration will be roughly predictable.

Thing is, if its a constant power, and the power curve is linear then its going to progressivley accelerate and be boring. What you need is a 92, cbr900, the first R1s etc, or even kevin schwantz's old bike (suzi). These machines had linear power curves, but the torque curve was a random number based on the day of the week

You'll hear magazine writers say that the bike was 'flat' and lacked passion. Often you'll see that the torque/power curve is flat an linear as well.

Then there are carb based bikes that have different rates of torque, the journos will say things like - savage delivery, unpredictable (I think fun) - you'll see torque curves at really silly places.

[marty]

look here>>> http://reviews.ebay.com/How-a-2-stro...00000000014651

and power bands only work properly once they are tensioned with a long weight, as opposed to a short weight, which is something as an apprentice, you would be unlikely to be able to find a part number for.

[pritch]

Probably to start off another argument,

I get the impression that if you really wan to start an argument you should place the controversial statement near the beginning of your post where those with short attention spans might see it

[Beemer]

Oh for heaven's sake, if anyone on an RG150 thinks they can drag an R1 off in a race (not a car of any make or model, but a BIKE), I'd like a bet on the outcome! I had one for four years and while I admit it was a lot of fun, there was NO WAY IN HELL I could have got the jump on a more powerful bike. If you guys reckon you can, I reckon you're full of shit!

[GNR]

wow, lots of replys,
thanks for that guy/gals, i was hopein for somthing more exciteing, but i see how it work,

another important fact to add to the brain

[crash harry]

The confusing bit is that a powervalve is often called a powerband.
Just my 2c worth

Really??? Only by someone who's getting the words confused together I think...

EDIT: Just realised that that sounds really sarky... wasn't really meant that way...

[Mattyc]

on a 2 stroke, the powervalve (on my bike anyway) increases the exhaust timing by opening a flap at mid rpm that actually makes the exhaust port higher in the barrell, this gives the bike a good hit

the pipe on the other hand has a lot to do with it too, the pipe works sort of like a supercharger and the exhaust waves reflect back into the engine forcing unburnt fuel into it, with the pipe its all about length , I race model powerboats with 10cc methanol engines, that also run a percentage of nitromethane, boats are around 12lbs and do about 80kmh or more when tuned right, we run pipes with expansion chambers , the shorter the pipe generally the longer it will take to get on pipe (powerband, rubberband, whatever) but when it does it will hit harder, the longer the pipe it will generally get on pipe quicker and have a more gradual powerband with less hit... the rule of thumb is for mixture - long pipe leaner mixture, short pipe, richer mixture (fuel air, not fuel oil)

word