gs750 520 conversion - number of sprocket teeth

[LarsKroghStea]

Hi,
I have a thread here: http://www.thegsresources.com/_forum/showthread.php?236916-1981-gs750-(gs750e)-Retro-Racer-project for my gs750e cafe-racer project. I'm fitting a 150/70-18 tyre on a stock gs750 rear hub laced to a custom made SM Pro Platinum 4.25 inch rim. To get as much clearance as possible, I'm converting to 520 chain and sprockets. I've calculated that the new sprockets need to be 17t in front and 49t in the back to maintain the same diameter as the original 15/41 combo. Previous owner mounted a 14/43 combo, and I think that gives a bit too much revs at highway-speed, but I'm thinking of buying a 16/49 combo.

What do you gurus think?

 

[tkent02]

Hi,
I have a thread here: http://www.thegsresources.com/_forum/showthread.php?236916-1981-gs750-(gs750e)-Retro-Racer-project for my gs750e cafe-racer project. I'm fitting a 150/70-18 tyre on a stock gs750 rear hub laced to a custom made SM Pro Platinum 4.25 inch rim. To get as much clearance as possible, I'm converting to 520 chain and sprockets. I've calculated that the new sprockets need to be 17t in front and 49t in the back to maintain the same diameter as the original 15/41 combo. Previous owner mounted a 14/43 combo, and I think that gives a bit too much revs at highway-speed, but I'm thinking of buying a 16/49 combo.

What do you gurus think?

What are you going to use the bike for? Back roads where acceleration is what you want? Mountains and corners? Long highway blasts at 180km/h + all day long?

 

[LarsKroghStea]

What are you going to use the bike for? Back roads where acceleration is what you want? Mountains and corners? Long highway blasts at 180km/h + all day long?

I do want acceleration over top speed, but I also want to cruice at 100-110 km/h at comfortable revs.

 

[tkent02]

Comfortable revs, it's a GS, it's comfortable at any RPM. 100 - 110, **** that's less than 70mph.

I'd go for the quick acceleration and let it spin on the road. GS loves to spin. They are inefficient at lower RPMs anyway.

 

[LarsKroghStea]

Comfortable revs, it's a GS, it's comfortable at any RPM. 100 - 110, **** that's less than 70mph.

I'd go for the quick acceleration and let it spin on the road. GS loves to spin. They are inefficient at lower RPMs anyway.

And what would be the best combination of sprockets then? For a 520 conversion..

 

[LarsKroghStea]

And what would be the best combination of sprockets then? For a 520 conversion..

Think i figured this one out my self. Found a table for gear ratios and the 14/43 combo that is on now gives a gear ratio of 3.07. The 16/49 combo in 520 pitch will give a gear ratio of 3.06 wich is close to the acceleration biased gearing I have now. Thanks for your input

 

[LarsKroghStea]

These are the ebay-items I went for :

Front 16 tooth sprocket : Vortex Front Sprocket 16T 3270-16
Rear 48 tooth sprocket: JT SPROCKET JTR1825.48 48 Tooth
Chain 118 links (calculator says I could use 116 links, but I'd like to be on the safe side).
This is the narrowest 520 I could find at a reasonable price: DID 520x118 Links VX2 Pro-Street Series Sealed X-ring Natural
This chain is rated to 750cc and 110hp.
The 16/48 combo gives a gear rate of 3.0 wich should be spot on.

I chose JT rear sprocket for low price and strength. Other choices are Vortex Aluminum(not hardcoated) and Supersprox Stealth

For a complete (I guess) list of which bikes that use the same pattern (pcd 100, id76, hole10,5) as the gs750 read this thread:

http://www.thegsresources.com/_foru...t-to-fit-GS-sprocket-carrier&highlight=RF900R


I will be fitting this to my gs750 with 150/70-18 tyre on 4.25 rim. You can follow my build thread to see if/how much offset is needed for this setup.