Sprocket Size for 630 to 530 convesion

[dcb]

I have a 1980 GS750E that I would like to do a chain conversion on. I am going from a 630 to a 530. My current sprockets sizes are 15/41. What sizes would give me the same power ratio using the 530 chain? Also if I wanted to increase the top end just a little, what sprocket sizes would I use then?


Thanks,

David

[Steve]

My current sprockets sizes are 15/41. What sizes would give me the same power ratio using the 530 chain?

Uh, let's see...that would be...uhhh, oh yeah, 15/41. 8-[

The chain will be narrower and lighter, but the number of teeth will remain the same.

If you wanted to increase the top end, you would have to experiment. Some bikes will not have the power to pull top end and need taller ratios. Other bikes have plenty of power and can go the other way with the ratio.

If you just absolutely have to get that last mph to show, you will have to see whether you are able to hit redline in top gear. If you can't, either drop a tooth on the front sprocket or add 2 or 3 to the rear. Note that this will increase your rpm at any given road speed. This will only prove practical in racing situations. Most people are looking to reduce engine speed at a given road speed and don't really care about ultimate top end.

By the way, which side streets are you going to use for testing? :shock:


.

[80GS1000]

Uh, let's see...that would be...uhhh, oh yeah, 15/41. 8-[

The chain will be narrower and lighter, but the number of teeth will remain the same.

.

530 and 520 sprockets are smaller in diameter for a given tooth count, so a 15 tooth 630 sprocket becomes an 18 tooth 530 sprocket and a 41 tooth rear sprocket becomes a 49 tooth 530 sprocket. This is to keep the chain from dragging across the swingarm, and to keep the gearing ratio about the same as stock. http://www.z1enterprises.com/referen...n630to530.aspx

You could add a tooth to the front or drop 1-3 teeth on the rear to get a bit more top end, at the expense of lower end torque. My GSXR 750 is geared -1 in the front to get more acceleration off the line at the expense of top end speed.

http://www.z1enterprises.com/reference/chainsprockets.aspx

[Steve]

Thanks for the education. I have limited experience with chains, as my last chain-driven bike was traded in on a shaft back in April, 1979. \\/

I knew the chains were different sizes, but I had them wrong. The 630 and 530 will be the same width, but have a different pitch (distance from pin to pin). The 520 would be narrower, as well, it would be 1/4 inch wide instead of 3/8 inch. Because the pitch is shorter, 5/8 inch vs. 3/4 inch, yes, the sprockets will be smaller, for the same number of teeth.

Doing the math, the stock ration of 15/41 gives a 2.7333 ratio. The suggested ratio of 18/49 gives a 2.7222 ratio. You just can't get much closer without getting exact. 8-[


.

[txironhead]

Okay, let me throw a curve ball into all of these equations with a question of my own:-D:

1981 GS750EX, K&N pods, Stage 3 jet kit, V&H 4-1, stock ignition for now. I'd like the bike to accelerate decently, while still squeezing as much fuel economy out of it as possible. I'm not going to be doing 120mph runs on this bike, mainly around town commuting with the occasional 70-75mph run on the highway. I know the mileage is going to be much worse than stock with the setup it has, but it pretty much came that way.

I know it will have much more power than stock, but I really don't need a drag bike or street racer, just a decently quick reliable bike.

Again, decent acceleration (no wheelies or 1/4mi drags), comfortable 70mph cruising, best mpg I can reasonably expect. The stock 630 chain is not long for this world, and I'm planning on doing the 530 conversion and would like to know what size sprockets to get.

[dcb]

Thank you for your replies. The shop only has up to a 17 available for the front sprocket. So instead of a 18/49, what would I need to use on the rear if I put a 17 on the front to keep it close to stock?

Thanks,
David

[80GS1000]

Thank you for your replies. The shop only has up to a 17 available for the front sprocket. So instead of a 18/49, what would I need to use on the rear if I put a 17 on the front to keep it close to stock?

Thanks,
David

If I were you, I'd get the 18/49 to ensure good chain/swingarm clearance. Call Jeff at Z1 for all the details and parts you need.

[80GS1000]

Okay, let me throw a curve ball into all of these equations with a question of my own:-D:

1981 GS750EX, K&N pods, Stage 3 jet kit, V&H 4-1, stock ignition for now. I'd like the bike to accelerate decently, while still squeezing as much fuel economy out of it as possible. I'm not going to be doing 120mph runs on this bike, mainly around town commuting with the occasional 70-75mph run on the highway. I know the mileage is going to be much worse than stock with the setup it has, but it pretty much came that way.

I know it will have much more power than stock, but I really don't need a drag bike or street racer, just a decently quick reliable bike.

Again, decent acceleration (no wheelies or 1/4mi drags), comfortable 70mph cruising, best mpg I can reasonably expect. The stock 630 chain is not long for this world, and I'm planning on doing the 530 conversion and would like to know what size sprockets to get.

IIWY, I'd keep the ratio close to stock - you want the middle ground between acceleration and top end power. What size sprockets are stock on your bike?

[txironhead]

15/41 630 stock

[80GS1000]

15/41 630 stock

18/49 then.

[dcb]

I currently have 15/41 on the bike.

Thanks,
David

[dcb]

If 17 is the biggest front sprocket I can get what would the right rear sprocket size be?

Thanks,
David

[80GS1000]

If 17 is the biggest front sprocket I can get what would the right rear sprocket size be?

Thanks,
David

47 for the rear and 17 for the front would work too. Gear ratios are calculated by dividing the number of teeth on the rear by the number of teeth on the front. So your stock ratio is 41/15 = 2.722, 47/17 would be 2.76, which is pretty much identical to stock.

When I did the 520 conversion on the GS, I went with 48/17 for a ratio of 2.84, for a little extra grunt off the line and a little extra chain clearance.

[dcb]

Thanks for the help. I just ordered a 17/47 with a spacer an an o-ring chain. Total came to $138.

David

[BlackandBlue]

I went up one tooth on the front sprocket not long after I bought my 83 GS1100E in 92. Helped a lot when on the highway. This torque monster has no problem handling the higher gearing.