I need some help understanding sprockets. My front sprocket was stolen, so I'm trying to figure out what size I need to order when I get a new one. When I bought my bike, I was told that the rear sprocket was 8 teeth bigger than stock. So the front sprocket, how much do you think It would have gone up in teeth? I've heard that people play around with different sizes to get an optimal ratio between the sprockets (is this true?) to have the most torque, and highest top speed, etc. And I keep reading about this 520, 525, 530 pitch crap for the rear sprocket...can somebody explain to me what that is? Thanks.

 

The sprocket sizes form a ratio. For every one turn of the front sprocket the rear sprocket turns a fraction of a turn.

If you think about pulleys - if you set it up to make it easier to lift something, you have to pull the rope further.

On a bike, same thing. Going down on the front or up on the rear makes it easier to turn the rear wheel, but it takes more rotations or in otherwords, a higher RPM. You trade ease of acceleration by giving up some top speed.

The 520 chain is lighter... less rotating mass to accelerate. It is supposed to be faster - but we're not talking much in terms of street use.

8 teeth bigger on the rear is a large number. Was it used for stunting?

My bike is an F4 and I run -1,+2... for ~14% change in ratio (I also went with the 520 chain). I think the F4i stock sprockets are slightly different. The F4 is stock 16 front, 45 rear. I think the F4i is 16 front and 46 rear with 525 chain.

Also note - when you change the sprockets the speedometer will be wrong. To fix that you'll need something like a speedohealer.

 

He said he put it on there because he wanted to stunt it, but never ended up doing it. It pops wheelies like a mother too. And yea, my speedo is pretty off. I'm used to that because of my jeep though, so it never bothered me.

 

It isn't just the speedo - it's also the milage on the odometer... and it's the inability to figure out how much further you can get on a tank of gas (for us touring types).

I like having a good guess at how fast I'm going

Do you want to keep that size sprocket, or go back towards stock?

 

I'm trying to figure out why in the heck would someone "steal" a front sproket. That's an odd theft.

 

Stole the sprocket, tank, seats, good fairings, radiator, etc. I left my complete bike at a friend's friend's shop after it got wrecked, and when I got it back, all of that was missing. He took the front sprocket too for some reason, which is why I'm trying to figure out what size it was. I have a stock sprocket that came with the bike too, but I have the chain that was with the big sprocket. I'm trying to keep the amount of money I have to spend to get it running again low, so I figured i'd get another front sprocket to match the big rear one since I already have a chain that fits. I know it was stupid to leave it in the care of someone who I didn't know, but I thought he owned the shop (turned out he had JUST sold it as of Jan 1, but still had access to it). Learn from your mistakes I guess.

 

Standard stock sprockets. 16 in the front and 46 in the rear.

 

So if I had 54 teeth in the rear, what size sprocket would most people put on the front?

 

Not a mistake on your part. Theft affects us all.

 

My advice would be for you to just buy a chain and sprocket kit. It'll include both the front and rear sprocket and a new chain. Bike bandit will even let you pick the sizes of sprockets you want, and they'll tell you the stock size too