unless they have a noise tester which i very much doubt (not even sure of a legal limit to be fair)
they would more than likely give you a vehicle defect notification that means you have to take the bike to an mot station at your own expense and get them to stamp it to say it legal and then you have to produce the stamped peprwork at your local stn in 14 days to prove it all good....
worst case but i am not trained to say 100% they could pg9 it as unfit for the road and seize it and apply a fine to get it back with conditions to get it road again...
but that is usually for unsafe vehicles.
You definately would not get a PG9. Additionally PG9's do not come with a fine per se. They are also issued 95% of the time by VOSA vehicle inspectors since there are very few police trained to the level required to be able to issue one. PG9's are for vehicles which are of such an unroadworthy condition that they present a danger to all members of the public by being allowed to continue on the public highway in their present condition and are usually only issued to commercial vehicles i.e trucks and coaches.
Noise limits vary dependent on the year of manufacture of your bike, but the generally accepted guideline for road use is 96db. Deano is quite right that the likelihood of the police having a db meter with them is remote to say the least and even more remote that they know the exact manner in which a db test has to be carried out as per Construction and Use law. Angle, distance, revs in accordance with the number of cylinders etc etc
When it comes to baffles, how do the police tell if you have removed them or not? If they are held in via a bolt hole, then it would be obvious to one who knew, if by a circlip then less so.
As long as it isn't stamped "NOT FOR ROAD USE" as clearly that is an immediate cry of it's illegal.
There are no points for an illegal exhaust under construction and use rules. It is dealt with via the vehicle defect rectification scheme (if your police force have adopted it) and will involve the 14 days as Deano has rightly said. It can also include a fixed penalty fine.
The only Construction and Use misdemeanours that carry an endorsement of points onto your licence are:
•CU10 Using a vehicle with defective brakes 3 points
•CU20 Causing or likely to cause danger by reason of use of unsuitable vehicle or using a vehicle with parts or accessories (excluding brakes, steering or tyres) in a dangerous condition 3 points
•CU30 Using a vehicle with defective tyre(s) 3 points
•CU40 Using a vehicle with defective steering 3 points
•CU50 Causing or likely to cause danger by reason of load or passengers 3 points
•CU80 Using a mobile phone while driving a motor vehicle 3 points
Me, I like noise :thumbup