'79 GS750 - 530 conversion

[mattfeet]

I am planning on doing a 530 chain conversion on my GS750 and I would like to re-gear for a little more pull around town. I don't really ride my GS on the highway much so I figured changing the ratio a bit would help me out at non-highway speeds. My question is, and I did search, what would be the best front/rear sprocket setup given my aforementioned requirements? I don't want to go crazy aggressive but would like a bit more low-end.

Matt

 

[tkent02]

Drop one on the front and see how you like it. Wait, do you have the stock sprockets now or has someone put taller ones on?

 

[mattfeet]

Stock AFAIK

 

[tkent02]

One on the front is about like three on the back. It's a fairly large change in how it feels.

 

[CivilRock]

Stock is 15/41 which is a 2.733:1 ratio.

Most people just talk in 2.733 and leave off the ":1"
So going up to 3.500 is too much, and you have to shift too much.
going to 2.9-3.1 would be good.

You also want to keep the physical dimensions of the sprockets close to stock if you want to keep the same handling characteristics. Believe it or not, smaller sprockets with the same final ratio will change the way the bike squats on acceleration.

17/47 is is 2.765 and pretty close to the stock ratio and size.

So, you either go up in the back or down in the front for more city time pull.
Like 17/50 (2.941)

Another thing to consider is front sprockets are about $16 and rears are about $50. So buy a 16 and a 17 front and then a 48-50 rear and you can swap them around as long as your chain is in the middle of the adjustment range.

2.5 = super slab cruiser
3.5 = 1/8th mile drag racer and almost stunt bike range.

-kevin

 

[mattfeet]

17/50 sounds good to me.

 

[mattfeet]

Also, I believe Im looking for a 114 link chain, right?

 

[celtic.ink]

I am also looking to do this conversion. I suppose 13/43 would be a little too aggressive, then? I want a good amount of pull, but will be on the freeways a fair amount as well.

 

[Guest]

I am also looking to do this conversion. I suppose 13/43 would be a little too aggressive, then? I want a good amount of pull, but will be on the freeways a fair amount as well.

A 13 tooth front sprocket is terrible for chain wear and a 13 tooth 530 sprocket would almost certainly cause the chain to rub on the swingarm and damage it. Keep in mind that a 530 sprocket has a pitch diameter that is 16.7% smaller for any given tooth count than a 630 sprocket. That is why people like to go to a 17 tooth front sprocket when they convert to 530, it keeps the sprocket diameter close to the stock 15 tooth 630 and avoids clearance problems.

Go to at least a 15 tooth front sprocket to keep the chain/swingarm clearance (better yet a 16 or 17 tooth) and adjust your ratio at the rear. Personally, if I was spending "a fair amount of time" on freeways I wouldn't change the gearing more than one or two teeth at the rear from the stock ratio. I also don't like a bike buzzing away for no good reason. If you don't mind your bike screaming its guts out then go ahead and add several more teeth at the back.


Mark

 

[blowerbike]

just seen the OP is local to me...
i have a decent selection of GS 530 sprockets from brand new to used.
let me know...or not..


1-530x50T sprocket specialist aluminum brand new(fits GS models) $50.00

1-530x46T vortex aluminum sprocket(i call it new)1 mile on(fits GS models)..$50.00

1-530x48T sprocket specialist aluminum sprocket(well used)(fits GS models)..$25.00

i may have more...and maybe some fronts...

 

[celtic.ink]

This is why I ask lol. So taller on both sides is the way to go. Is a 530 chain conversion a good one to do? The reason I was considering 530 was because I found 530 sprockets that matched the faulty gearing info I had.

 

[blowerbike]

IMO
people go to 530 to save rotating mass.
if you go 17 front/50 rear per say...you will have a longer chain compared to the 630 that came on the bike.
i bet my azz that with the above numbers the weight saving isn't as much as people believe.
suzuki used 15t 530 fronts on a lot of newer bikes...GSXR/katana/bandit and so on.
IMO...16/45 ish don't sound bad and you don't have a mile of chain turning.
just food for thought...............................

 

[Guest]

if you go 17 front/50 rear per say...you will have a longer chain compared to the 630 that came on the bike.

I would like you to explain how the chain length changes if the wheelbase is kept constant and the pitch diameter of the sprockets is nearly identical. There will be more links in the 530 chain (20% more if everything else stays the same) but the overall length will be the same between 530 and 630.


Mark

 

[blowerbike]

15/42 630 chain is around 98 links i think.
how many links is a 530 17/50 geared bike?
i am comparing stock 630 to the modified 530 larger gear front and rear=longer chain on the 530.
do you see my point?

 

[Guest]

15/42 630 chain is around 98 links i think.
how many links is a 530 17/50 geared bike?
i am comparing stock 630 to the modified 530 larger gear front and rear=longer chain on the 530.
do you see my point?

As I said, the 530 will have 20% more links in it because the pitch is 5/6 of the 630 pitch. Having more links is not the same as being longer. I do agree with you that the weight savings won't be very significant.

Edit - After re-reading your post it seems that you think the 17 and 50 teeth 530 sprockets are physically larger than the 15 and 42 teeth 630 sprockets. Is that correct?


Mark

 

[celtic.ink]

I imagine that there will be a loss in tensile strength with a lighter chain. I guess what I'm looking for are opinions on what my options are for faster than stock acceleration. Doesn't have to be crazy fast, but I do want a little something extra.

 

[allojohn]

I imagine that there will be a loss in tensile strength with a lighter chain. I guess what I'm looking for are opinions on what my options are for faster than stock acceleration. Doesn't have to be crazy fast, but I do want a little something extra.

No loss in strength but gains in maintenance and longevity.

 

[celtic.ink]

Awesome. I think I will be looking into doing this swap over the winter. As you can tell, I am very new to all of this. That being said, if I went with a 17t 530 front, what would be a good choice/range for the rear if I want a bit higher than stock acceleration?

 

[Guest]

i am comparing stock 630 to the modified 530 larger gear front and rear=longer chain on the 530.
do you see my point?

Just in case you are thinking the 530 sprockets are physically larger than the 630 ones because they have higher tooth counts, have a look at this site: https://www.rbracing-rsr.com/calcsprocketdiam.html

630 pitch is 0.750" and 530 pitch is 0.625". From the calculator, we get:

15 tooth 630 sprocket pitch diameter = 3.607"
18 tooth 530 sprocket PD = 3.599"

42 tooth 630 PD = 10.036"
50 tooth 530 PD = 9.954"

As you can see, the 18 tooth 530 front sprocket pitch diameter is 0.008" smaller than the 630 and the 50 tooth rear is 0.082" smaller than the 42 tooth 630 rear. The reason the rear is smaller is that 50 teeth is not the correct equal size replacement, but is the closest full number of teeth. The correct number of teeth is actually 50.4 (6/5 x 42) but we have to make sprockets with complete teeth.

I imagine that there will be a loss in tensile strength with a lighter chain.

There will be no loss in strength, current 530 chain has been developed to the point that it is stronger than the old 630 that was around 30 years ago. MotoGP bikes run 200+HP through a 520 chain under severe conditions, so your GS will be more than OK with a quality 530 chain. The newer O- and X-ring designs also last much better, going 30,000+km for me on two bikes with very minimal maintenance. Keep it clean and rust free and your chain will go for years.

That being said, if I went with a 17t 530 front, what would be a good choice/range for the rear if I want a bit higher than stock acceleration?

If you want to use the 17 tooth then I would suggest a 50 or 51 tooth rear. It is often suggested to avoid sprocket combinations that provide even ratios though, and 17/51 = 3.00:1, so I would say the 50 tooth is the better choice.


Mark

 

[blowerbike]

As I said, the 530 will have 20% more links in it because the pitch is 5/6 of the 630 pitch. Having more links is not the same as being longer. I do agree with you that the weight savings won't be very significant.

Edit - After re-reading your post it seems that you think the 17 and 50 teeth 530 sprockets are physically larger than the 15 and 42 teeth 630 sprockets. Is that correct?


Mark

i will reply once i compare the sprockets we are speaking of as i do have all of these on hand and i can make a direct comparison on diameter.