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I just recently purchased a 02 with 9k mi and am looking at changing the chain and sprockets. I am a little confused with the kits which say 520 / 530...etc. what would be a good street combo?
 

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For the street, I'd stay with the 530.
The 530 is the same pitch as the 520 or 525, but is wider and spreads the force across a wider sprocket area.
Now for racing, sure, go with a 520 or 525 as the chain is lighter in weight.
I measured the 530 chain for my bike and it weighed around 4 Lbs.

The stock final ratio is way high for in-town use.
For the street, a very good all around final ratio is 15F/41R.
I have it on mine and it works great, both in-town and highway.
It makes the speedometer about 7 MPH optimistic, but that can be fixed with a Speedo-Healer unit.
 

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DID 520 EVR3 chain....go look at the 520 vs 525 vs 530 specs on the D.I.D. site and you'll see the 520 ERV3 chain is all you need.

My 520ERV has been on my bike for about 10,000mi and I've had zero problems with it.
 

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I have 15/41 final gearing and a 190/55-17 Pirelli Corsa III rear tire.
According to my gearing calculator and measured circumference of my tires, my speed at 4000 RPM is 67 MPH. At 5000 RPM it's 84 MPH.

Now for a 15/42 combo with a 190/55 tire, I calculate 66 MPH at 4000 and 82 MPH at 5000.
A 190/50 tire will be slightly shorter and the MPH will be slightly less.

So either way, the RC51 will be lazily loping along at those speeds in 6th.
At 70 MPH in 6th, the RC51 is barely in the torque range and not even in the HP band.That's not until 100 MPH and 6000 RPM.

Need to make pass on the freeway? Drop it down to 5th and run it up to 120 MPH (8000 RPM), hit 6th and keep on rockin' up to 155+.
All the while hearing those pipes booming. I love it.
 

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How high are the rpm's on the highway?, say at 70mph with that 42T sprocket!
Well at 70mph(85 on speedo) its right around 5000rpm + or - some change

So either way, the RC51 will be lazily loping along at those speeds in 6th.
At 70 MPH in 6th, the RC51 is barely in the torque range and not even in the HP band.That's not until 100 MPH and 6000 RPM.

Need to make pass on the freeway? Drop it down to 5th and run it up to 120 MPH (8000 RPM), hit 6th and keep on rockin' up to 155+.
All the while hearing those pipes booming. I love it.
You've been saying some weird things lately. First off the 51 is not "lazily loping along" at 70mph in 6th with a 15/42 setup. I don't know if you've ever done the 15/42 cause I've only read that you have 15/41 but you'd be surprised what that one extra tooth will do. Before with stock gearing I would have to downshift into 5th sometimes 4th to make a pass. Now I don't I can leave it in 6th with no problems. And 4K rpm and above are this bikes sweet spots. What your failing to mention is that with the gear change your going to reach the higher rpm's quicker. And why in the world would you just run it up to 8K in 5th then make the switch? This bike makes power all the way to redline. Run it up to 10K rpm and then make the switch.
 

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I don't run the 15/42 combo, only the 15/41.
I only calculate 2 MPH difference between the two, so they're relatively close.
So if you're traveling down the freeway at 70 MPH and the tach is registering half or slightly over half rated RPM, I'd say "lazily loping" at 4500-5000 RPM could be a apt description for an RC51.
Instead, how about "happily humming"? :)

The soft rev limiter cuts in at 9250 and the hard limiter at 10,200.
I've never had a reason to rev it to 10K.
It's the mechanic part of me that doesn't push the hardware to the limits.
 

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Im just orderd 15T/41T,..Im wondering if I should of gone with a 42T????
mostly street riding!
It all boils down to what kind of terrain you ride on.

Here in Florida, it's flat with rural roads and highways.
For me, the 15/41 combo works. More than enough top end on the highway to land me in prison, yet I have no problems through the twists and turns on the rural roads. I use 2nd through 6th in the course of that ride.
My RPMs generally range in the 4000-8000 range since I'm just out to have nice ride while trying to maintain fuel consumption.
Now if I was at the track, it's different. I may change the ratio to 15/42 or even 43 if it needed it to allow the bike to just hit the rev limiter at the end of the longest straight.

Now if you live in the mountains, or your roads are predominately tight and twisty, then maybe a 15/42 may allow the bike to stay in it's power range better through the gears.

Try it and if it doesn't work, change it.
 

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It all boils down to what kind of terrain you ride on.

Here in Florida, it's flat with rural roads and highways.
For me, the 15/41 combo works. More than enough top end on the highway to land me in prison, yet I have no problems through the twists and turns on the rural roads. I use 2nd through 6th in the course of that ride.
My RPMs generally range in the 4000-8000 range since I'm just out to have nice ride while trying to maintain fuel consumption.
Now if I was at the track, it's different. I may change the ratio to 15/42 or even 43 if it needed it to allow the bike to just hit the rev limiter at the end of the longest straight.

Now if you live in the mountains, or your roads are predominately tight and twisty, then maybe a 15/42 may allow the bike to stay in it's power range better through the gears.

Try it and if it doesn't work, change it.
Thanks for the info. subsailor!, I live in central ohio and its pretty flat with alot of highways also. I'll just try this for awhile and if i dont like it i'll just swap a 42 on there!
 

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any veteran rc owners on here that used to frequent motorush aka rc51.net?
this was a huge issue for what seemed like forever. i cant remember who it was that posted all the research, but the way it broke down was like this...the rc51, god love it, doesnt have the power to pull to redline in 6th gear with the stock gearing. the best ive heard of is 171mph, but if you drop to 15/42 it will pull all the way to redline getting you around 182mph. SO, why worry about how much its spinning if you change the gearing, you got more top end, and you are quicker off the line, and when youre droning in town or in a residential or school zone, you are not lugging it in first gear because its so fling-flangin tall. story told, if you are buying a new chain, you have to get sprockets anyway, so get a quality 520 chain and 15/42 gears.(period)

jt
 

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All my questions were answered here, just one question why do we have to change the front sprocket can't we just change the rear? If I definitely need to change the front sprocket how hard is it to replace? do I need to take it to a shop? does it need special tools?

Thanks,
 

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You don't have to replace the front. You can just replace the rear.
Here's a comparison:
15/41 = 2.733 16/44 = 2.75
15/42 = 2.80 16/45 = 2.81
15/43 = 2.866 16/46 = 2.87

If you notice, on average, 1 tooth change in front equals 3 teeth in back.
 

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I just ordered a 15/42 set. Iw as just trying to stay away from replacing the front which might be more complicated. Never worked on a bike before always has been on cars.

Thanks,
 

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Well the front sprocket is easy to remove. Just remove the cover and the bolt in the center of the sprocket. Dont know the tourqe specs. If you look online you can find a PDF on the service man....
 

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Be aware that the slave cylinder for the clutch release is located in the front sprocket cover. Do NOT squeeze the clutch lever with the cover off!!

Front sprocket bolt torque is 40 Ft/Lbs. or 54 Nm.

Some slide a end of a board between the wheel spoke and swingarm bottom to hold while torquing the sprocket nut. Others might use the rear brake.
 

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I've read somewhere you can go to a 42 T rear without changing the chain. If you drop the front to a 15T, can you still keep the chain and do a 43T?
 

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I've read somewhere you can go to a 42 T rear without changing the chain. If you drop the front to a 15T, can you still keep the chain and do a 43T?
You might be able to get by with a 15/42 without chain length issues.
I'm not sure about the 15/43 combo as I run a 15/41 and never tried it.

With 15/41 on an SP2, the axle is a little past mid-point in adjustment (around mark 3 from full rear) with good chain and sprockets.
You may have enough adjustment free space to run a larger rear sprocket.

I'm sure you may get a response from those who do run a 15/42 or 43 if they had to use a longer chain.
 
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