Chains, Gearing, and Sprocket Combos Derp-Mystified

Since I recently came into posession of about a billion sprockets, I thought I'd do a little blurb on sv650 gearing. 

tl;dr: 15/43 will give you lower rpm at cruising speed. 15/47 will make you accelerate really hard but keep the rpms high on the highway. More teeth in the rear=wheelies. Fewer teeth in the rear= Low highway RPMs. Mostly leave the front alone

A few things to look at with gearing. Front sprocket size, rear sprocket, and chain pitch. 

Pitch... 520 conversion, 525 stock, 530 conversion?

Pitch is the easiest with svs. Both 525 and 520 have the same link length (15.88mm which is 5/8 pitch... thus the 5!!!) but the inner width or sprocket width are 1/4" for 520 and 5/16 for 525.
What does that mean? That you can slam a 525 chain onto 520 sprockets? Well you *COULD* and it would even work for a while but that would result in fairly quick wear and a good chance of the chain peacing out... You definitely can't slam a 520 chain onto 525 sprockets cause it will be very tight. 

The general consensus on chains is that 520 is lighter (and wears faster) and 525 is heavier but lasts longer. You know what else will really decrease chain life? Having it super tight. Or really loose. Or dry. Or rusty. Almost every partout bike I get has a completely cooked chain cause nobody ever bothers to maintain them.

So, if you're looking to save grams... 520 is your speed. Or 525 is gonna be just fine for any street guy. 

One rare and insane to me conversion is 530. The sv650 really doesn't put down enough power to need it. You'll still rust-out faster than stretch it, and I'm not quite sure what sprockets/tires/spacers will do with a wider chain. Probably some chain bite... that's when the chain eats the tire... #supermotolife heh

Front vs Rear Sprocket Sizes

stock sv650 S models have 15 front, 44 rear gearing. N models have 15 front 45 gearing. Because wheelies? Or did suzuki assume that S guys spend more time on the highway and want lower rpms but N guys ride around the city and want more oomph? 

So what happens when you fiddle with the rear size, or front size, or both? Keep in mind, there is no magic gearing that works everywhere. For racers, it depends on your shift points and power... a popular choice is 15/43 or even 42. For street it depends on what you ride more. Do you need the acceleration, or cruising rpm? On the 650 you will USUALLY run out of power before running out of gearing so it really won't give you much more top end speed no matter what you go with, it will just get there in a different way. Personally, I like 15/45 because I like hammering on the throttle out of a corner and very rarely ride highway.

As you increase the rear tooth count, you get more acceleration at the cost of higher rpm per mph. If you go too high, you may even run out of redline before running out of power. You may at a certain point also need a longer chain (or bring the adjusters forward). 

As you decrease the front tooth count, you get the same thing. more acceleration at the cost of higher rpm per mph. A WARNING THOUGH... If you go 14T front. or especially 13T front, the chain drags harder on the chain guard and has to take a tighter path around the front sprocket. This means more wear, and eventually eating through the chain guard and cutting into the swingarm. 

The opposite is also true. A smaller rear means slower acceleration, but lower rpms at highway speeds. You'll run out of power before running out of gearing. Or a larger front gets you the same. 

Look at the chart below. A stock S 15/44 is 2.93 front revolutions per 1 rear revolution. If you make that a 15/48, it's 3.20 revolutions. So the engine spins more to make the rear spin less. Good for acceleration and wheelies. But that means about 10% higher rpm everywhere. So if 80mph was 7000rpm it's now almost 8700. (or something... i don't know what the actual speeds to rpms are).

You also now need a chain that's 2 links longer. The funny thing though, to achieve the same wheelie-central gearing, you can do a 14 front 45 rear. And now no need to extend the chain. Just keep an eye on the chain guard... 

just keep in mind... Wheelies are bad for SVs' motors.