Hey guys i just put a 15 tooth sprocket on and i was looking to get a 48 tooth for the rear. My chain is almost new will i need a new one or will this one fit.

 

Assuming your current chain is a 108 link chain, it should still fit.

 

I thought whenever you change sprockets you HAVE to change or the chain too?

 

You don't HAVE to change anything when swapping driveline componenets, its recommended. Some people take recommendations as gods spoken word.

 

Agreed Bored. I didn't have to replace my chain when I did my new sprockets but the chain needed replacing anyways so I went ahead and did it.

 

Was thinking of doing the same thing, my chain looks perfectly fine and was gonna just do the sprockets, my buddy keeps telling me it's night and day. The bike is plenty fast, curious what else this does. Next up is leathers, track day and girlfriends approval! Ha

 

your speedometer will be off and you will lose top speed, and revs will be higher if you are traveling interstate speeds.

 

Revs will be higher at any speed.
So in conclusion a -1/+2 will make a bike that doesn't really need to be any faster exactly that, faster, while reducing gas mileage, top speed, and engine longevity. For a track bike it can make sence, for a street bike I just don't understand.....

 

So on that note would you suggest +1/-2 then to make the bike better

 

I did this swap when I needed my chain replaced. Cause I guess it's against motorcycle commandments to just replace the chain and not the sprockets. Anyways, this gives me a bit more bottom end power, so I can be cruising around town in sixth gear going about 40 mph. I don't see why this would decrease the longevity of the bike. So if someone who is more knowledgeable in this area should explain as to why this would decrease the longevity of the bike. Cause the RPM difference at cruising speeds (about 65 mph) is only about 700. As to worse gas mileage, I seem to be getting better gas mileage with the new sprockets (about 53 mpg). This is from my experience so far. Hope this helps.
Oh and btw I only did a -1/+1 to keep the chain the same size as stock in case I want to swap back to the original sprockets.