Topic approved.

see with a bigger rear sprocket you get a little more acceleration but top speed decreases . see what you want top speed or accel .

You running the chain without the chain guard is a major reason it has worn out faster than it should. Your chain is not an O Ring Chain and it does not maintain lubrication when exposed.

If you go for a P200 sprocket then your gearing ratio will drop alot I think.

Some questions:
What are the sizes of your stock front/rear sprockets?
What is the major reason for you wanting to change sprockets?

EDIT: I suggest you don't go for a P200 sprocket. If you do want to go for it, make sure you know how to calculate gear ratios.

See P200 sprocket is 38T.

Assuming P180 sprocket is 43T.
Assuming the same size front sprocket is used for P180.

If you put P200 sprocket at the rear, you will have taller geared your bike. Which means your top speed in each gear will increase. Engine will be spinning less than before for a designated speed in each gear.
Benefits from this are : top speed increase. Increase in mileage.
Disadvantages: acceleration will drop. Roll on figures will drop.

If you put a bigger sprocket (like a 46T), you will have shorter geared your bike. Which means your top speed will decrease in each gear. Engine will be spinning more than before for a designated in each gear.
Benefits from this are : acceleration will increase. roll on figures will increase.
Disadvantages: Top speed will decrease. Mileage will drop.

Can't make it simpler than this.

Thanks for that Pranay...
I actually was planing on the entire P200 sprocket kit. front & rear sprocket and chain. Not the rear sprocket alone. Now I dont know how feasible that would be. I dont want a drop in mileage because I already am running on a k&n and planning to upjet to the ZMA's jets.
SO I think I would settle down with the P180's entire sprocket kit.
I just asked this because I read somewhere that the new P180UG4's sprocket kit is adapted from the P200.
Pls do comment on this Pranay

The new p180ug4 has sprocket setup of 14 front and 39 rear while the P200 has 14 front and 38 rear.
The 180 ug4 setup will be slightly taller on the 180 ug3 provided u use the stock tyre (100/90), The ug4 comes with
120/80 tyre setup which had made the gearing go short from ug3 so bajaj has revised the ratio by sprocketing.
Considering you are running a modified engine setup, you better go for the 180 ug4 sprocket set, check if its a direct fit it comes with O ring chain and also a slightly taller gearing which will be useful for you.

my p180's UG2 sprocket change is long overdue as i always wanted to get a p200's chain sprocket kit to be installed.. although the 200's chain need a lot more maintenance then a covered non O'ring chain.. but i am ready to bear that... now i have one more option to go for 180UG4 chain kit .. does it have a 6 hole hub in the rear wheel or 4 ??

Even i am looking to do something similar. just want a confirmation if p180ug4 or p200 sprocket kit is a direct fit? if not! what else i need to alter to get it fitted right?
where can i do this stuff in pune?

my bike is p180 UG2 2006 model. done 33K. still havnt changed the chain or sprocket a single time.