Upgraded sprocket/chain

[gspower]

Hi all,

postman_pat just gave me the last bit of info I needed to rebuild my front brake caliper. Now I'm moving onto replacing the rear brake shoes. I will have to have the tire off and my chain has never been replaced (this is a 1979 .....) so I was thinking about changing the chain and both sprockets. I had read good things about Vortex and DID but was wondering if any members here have tried this on a similar sized bike. My low end acceleration is more than enough but my top speed is a bit low so I thought perhaps I would bump the rear sprocket down by a few teeth. Does anyone have feedback on this? Comments, stories, suggestions, or criticism? How do I size the chain if I change the sprocket?

Lots of questions ... I've never dabbled in this sort of mechanics. Excited, though.

Thanks a lot,
GSP

(Reposted into the correct forum)

[gspower]

Decided on 42 teeth in the rear, down from 45, and 16 in the front. Ratio changes from 2.8 to 2.6. Is this not drastic enough? Will I notice a top speed improvement?

[Steve]

Quick question, maybe you will see it before placing your order.

Is you top speed limited because you hit redline?

Somehow, I don't think so, meaning you are limited by POWER (or the lack thereof), not gearing.

In that case, you will need to ADD teeth to the rear sprocket to get your engine spinning where it can make another pony or two.

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[ShadowFocus603]

I'm hoping he went with a 530 conversion which will help with rotating mass and acceleration as well.......

[Steve]

I'm hoping he went with a 530 conversion ...

Did the 425s come with something larger?

I am ignorant on the matter of chains, it would just surprise me that they used the same chain on the 425 that they did on the 1000.

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[gspower]

Thanks Steve. No, I am not redlining. However the engine whines like a toddler when I am past 70mph. My lower gears are more or less useless except maybe for racing. I frequently switch from 1st to 3rd to 5th when accelerating. I was hoping that bumping down the rear teeth might help this, or at the very least lower my RPM's at the higher speeds. I don't even know what the top speed is because I've never pushed the bike that far.

I haven't placed any orders yet. Was JUST about to and thought I'd check on this thread. Shadow, the GS425 came stock with a 530 setup. I was actually thinking of converting to 525 but could not find the right setup on JC Whitney. Guess I'll stick with the 530?

Steve, anything else to add? Somehow I feel that adding teeth to the rear wheel will make me zip through the lower gears even more. Am I incorrect in this assumption? I've never toyed with sprockets so don't have much experience with this sort of thing. With my goals in mind, what setup would you recommend? Currently running 16 teeth in the front and 45 in the rear. Bike whines at higher speeds and I'm zipping through the lower gears.

[gspower]

Last update, ended up sticking with the 45 rear but bumping the 16 front up to a 17. Dropped the drive ratio from 1:2.81 down to 1:2.64. It's not a huge change in any case and I should be able to squeeze the stock 104 link chain on as I've only added one tooth.



Thanks for all the input. I will let you know how it works out with pictures.

[Steve]

If you are doing that in an effort to raise your top speed, you will be disappointed.

Adding one tooth to the front is about the same as dropping three from the rear, so you will be doing the same thing you were originally thinking of doing by dropping the rear to a 42.

Your engine is "whining like a toddler" because it NEEDS to. You have a small bike that doesn't make much power. What power it does make happens well above 5000 RPM. You will definitely lower your engine speed relative to road speed, but I think you will find that your gas mileage will decrease in the process, too. Why? Because you are operating in the range where you have less power, and will have to hold the throttle open farther, just to get enough power to do what you need.

You asked for my recommendation? OK, here it is: Get used to your engine whining like a toddler.

You want something that piddles along at low RPM? Get a Buick. This is a GS, let it sing.

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