Think it means "if you've got one (or more !) pillion passengers, the bike won't perform as well"

No I mean to say that a bike is being used by two different persons with or without a pillon rider at a time.

Sounds unlikely to have much effect, although I could imagine two riders producing different wear patters on the tyres...but you'd have to be a pretty exceptional rider to notice the difference.
Just a cat's guess...

Del

Oh ! you're right but I think different driving habits lead to change in the performance.

I don't see how unless something like excessive reving causes premature engine wear, or doing wheelies knackers the clutch. The variation of 'normal' driving shouldn't make much difference, unless of course the engine management system 'learns' the rider's style... but I doubt that.
Dropping it on a corner is the thing most likely to effect performance...running into a wall will effect the handing too.
Mind I can't imagine too many people sharing bikes...
Del

I don't ever recall using the clutch to do a wheelie though I've had more than a few successful clutch shifts while doing an extended wheelie The faster you go the easier to keep it up to a point after which it's hard coming down

I don't ever recall using the clutch to do a wheelie ..
Yeah...you were probably driving something bigger than a gutless 250cc single cylinder 2-stroke.

Many two wheeler designs are specific to keeping the front wheel down on the ground but I never had any of them

And a 250cc was my favorite wheelie machine...

Bikes are usually not that sensitive to changes in riders. I would say riders are more sensitive to changes in bikes. I know after riding a dirt bike and then getting on a full dresser definitly changes the feel of the bike and your reaction to the changes. Two totally different worlds!

a full dresser ???
Ever tried riding a wardrobe? (That's what a Lambretta with a load of suitcases on the back rack feels like)
Del

Thats a scary vision. Hope it wasn't as I imagine it.

Yeah, I got the scooter equivalent of a tank slapper going round the a reallllllllly looooong bend at the Devil's Punch bowl Hindhead. You can see the bend on the map...it's that BIG kink on the A3
Del

Yes the arguement is right

All the five fingers in our hand are not the same ;It applies to the driving style of different people

The mechanic might have adjusted your vehicle to suit your style of driving and when the other person drives it ;HE forces the mechanism in the bike to change it to his style and it goes on when different people drive it and finally at one point of time due to frequent change the engine performance reduces Then we have to retune the engine to get a better performance

HE forces the mechanism in the bike to change it to his style

Quit your day job comedy suits you...

Only two riders? Here in India whole family rides on one bike.Man is driver, wife is pillion rider, one kid on the tank in front of man, another kid on back seat with Mom. This made Mr.Ratan Tata to conceptualize "Tata Nano Car".

Are they already on sale in west? I'd like to get one if they're fuel economic and cheap.

Nano for west is still under development. It will enter U.S markets within 1/2 years.You may visit web:www.tatanano.com for more details.