i recently both a honda babyboy 2000.whenever i drive up to 100km/h,the steering wheel starts to vibrate.but upon passing the mark either faster or slower,the vibration stops.my friend also comfirmed it on his bullet.
i don't want to believe honda incorporated that into its car design,
can anyone please explain?

Go get a wheel balancing & alignment done. That should correct it.

Try wheel balancing and /or alignment

In addition to Wheel Balancing and / or alignment, check one or more of your tyres for replacement.

I have experienced that in the past, after alignment and balancing, the problem was not solved, so I checked my 4 tyres and took the best 2 out of the 4 to the back and put 2 brand new tyres at the front. Ever since, it's running very smoothly no matter the speed.

thanks a mil. will do that right away

Just a little more contribution on the topic, I also think u should do a wheel balancing and Alignment done, But u should be there while its being done, Some places utilize the new Computer based wheel balancing & Alignment systems. But sometimes those systems aren't a hundred % ok, Here is a better way of knowing if a good job has been done,
1. After the balancing has been done on a particular tyre (Especially Front)
2. Ask the vulcanizer to fit the tyre and tighten only two or three nuts.
3. While that tyre is still hanging in the air,
4. Get into the vehicle and engage the gear of your vehicle to (D3 or D2) (Automatic)
5. the tyre should begin to rotate and assume speed like if it was being driven.
6. Watch ur speedometer, it should start rising.
7. Once it gets to 100 & exceeds without vibrating, the u know they did a good job.
8. Do same on both front tyres since its a front wheeler.
9. U can also rotate and do same sequence for all tyres via the front wheel.
10. Sweet talk ur vulcanizer, cos they dont always like goiing thru dis process,
11. Goodluck

nothing much to say really.

I experienced the samething with my Camry 99 but during the wheel balancing and alighment, the guy discover one of my front tyre even though it looks new but was bad cos it couldnt pass the balancing test, so i had it replaced.    I am good to go at any rate without a hitch.

ADVICE NO 1.
Go do a wheel balancing and alighnment and take it up from there

all has been said here, wow guys get experience wooo))