Exchanging of OE exhausts will bring no positive result unless & until it's been physically damaged mate. So, would suggest you to change the bore kit completely & have a good night's sleep.

l ill update u soon about the exhaust and bore thing by this monday as i have exams going on

there is misconception in boring of small engines. It all depends on the lathe guy and careful running in. Remember in case of re bored engines the run-in can extend to even 5k kilometers.
My bike has run 2.8 lacs km. my engine overhauling was done at 1.25 lacs km.
at that time i changed into new bore piston and it served well for another 1.1 lacs km. even when i opened my engine there was hardly any smoke or oil consumption.
the next time when i completely overhauled my engine i went for new bore piston but this was my biggest mistake. The new kit was of manufactured defect and started consuming oil from the day it was put. the after 2000km the bore was opened and my mechanic and i was alarmed to see the ring gap.
Then a new oversize ring was inserted by grinding it to required gap.After about 13k k ms when i was going to my home, a distance of 120 km, it ceased on the way. But i continued without exceeding 50 k mph for next 500 km without any work.

then the bore was opened and my mechanic and i was surprised to see that the liner was completely damaged. Then he took my old bore to his trusted lathe guy. He bore in a different way and without the use of a boring machine but in a turning lathe by use of honing. he hones the cylinder and measures it by inserting the ring until satisfactory ring gap is obtained. There are many well known borers in our city who use many machines but all have defect in there borings.But this lathe guy bores in a simple way and charges only 70 rupees for it. I used mahle first oversize piston and this was specially ordered by a spares parts retailer friend of mine as there are duplicate pistons of mahle in the market.

Trust me after boring the compression became so high that most of the time i couldn't kick in one try. some the time the clutch would slip as if the clutch plate has worn and even 1 ml engine oil is not consumed.But the downside is that i had to wait for 5000 km for engine to free up otherwise it would lose power if ripped hard. but after 5000 km the engine is so perfect that it is much better than our new splendor and CD deluxe and returns a mileage of 80-85 km pl in city and once in highway it showed 98 km pl.

So i would like to say that re boring is always better than new replacement bore but the lathe guy should do the perfect job and original pistons of reputed company must be used(Mahle,Goetze, Escorts are some). Moreover in case of re boring if the piston is tight then you have to wait for nearly 5000 km for running-in to complete.

i changed the silencer but still smoke was coming had no time so came back home
ill go back tomorrow
n get the engine inspected!

and ya
the mileage is worst
giving less than 25 kmpl
and engine level is upto mark but became black
but the pick up and top speed didnt change at all

finally got the engine inspected
the piston n the bore got damaged
so got new bore kit
waiting for the run-in-period to finish

any advice on the run-in-period ?

- Go through owner's manual once again
- Don't accelerate hard for the 1st 1000 Kms
- Avoid running the engine continuously for more than 25-30 Kms for the first 200 Kms
- If possible, change the engine oil after 500 Kms & once after 1000 Kms.

^^ and keep varying your speed (upto 40-45) till 500kms. Then go for little higher speeds say 50-60 and vary your speed at that range (till 1000kms)

i will go at constant speed below 40
and no sudden speed bursts right ?
.

i changed the oil before 500kms i did the bore
so now shall i change the oil or not
read somehwere to change the oil after 1st 20-30 kms
is it true ?

no, no go for varying speed not constant. And shudden, short period (few seconds) brusts are ok.
And also oil changing has got different opinion from different people. Changing it very early is useless according to me so change the oil now & stick to it till 500kms

IMO never take risk,drain the old oil completely and fill it with new oil and keep it below 40 till 500kms and below 60 till 1000kms. keep it varying between 40 and 60.

@Honda_CBF
@Aneesh@4GHz

thanks a lot guys ill change the engine oil as soon as possible
and run below 60

.
ill post the riding experience after 1000 kms

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whats wrong ?

1. Stick to owner's manual, owner's manual & owner's manual. All other things such as changing at 20 Km, 200 Kms are half baked info!!
2. Sudden short burst, before 1000 Kms is excellent to damage the engine; human psycology also attributes a little here; once experienced a short burst, one always craves for more. If done unintentionally fine, but, not a regular practice.
3. Per manufacturer, the engine oil is to be changed once at 1000 Kms & every 3000 Km there after. However, it has been noted that there will be metal shavings from a new engine (but that's crankcase included, which is not in your case) & hence engine becomes rough; so its advised to change once during 500 Km mark. But this is necessary only if you feel the engine is rough

Needless to say, I've a 7 yr old Activa!!!

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im confused right now
with multiple suggestions

ill stick to
varying speed below 60
as all said
n change oil at 1000k or early
when i feel the engine is rough