Zongshen RX3: Sprocket Carrier Modification

[SpudRider]

Personally, I think the Zongshen RX3 is geared too tall from the factory with the stock, 14T/44T sprocket combination.

I am currently running a 13T/46T sprocket combination on my RX3, and I like it a lot. I really don't think there are many benefits to be gained by gearing the bike taller than the stock sprocket ratio, which is already very tall.

However, a 40T sprocket is not expensive, and it certainly doesn't hurt to experiment with different sprocket ratios. The only way to discover the optimal sprocket ratio for each of us, as individuals, is to experiment.

[peperino]

Picture
The thing with changing the rear sprocket, is that once I've cut the chain there's no goin back :(

[peperino]

This pic maybe helps a little more

[detours]

CSC is going to offer a 42T rear. That's only 2 teeth smaller than stock. I wonder if there's enough room in the axle adjustment to take up the slack.

[SpudRider]

Thanks for posting the photos, amigo. You have the rear cushion hub, which is the same rear hub we have in the United States. The JTR473.40 is a 40T sprocket which will fit your hub without any modifications required.

http://www.jtsprockets.com/catalogue/sprocket/JTR473



You can easily find this sprocket for sale by searching the internet; just type "jtr473.40." This sprocket is for sale on Amazon for $21.36, with free shipping.

http://www.amazon.com/JT-Sprockets-J.../dp/B005DL7JLO

You can purchase this sprocket, and it probably will fit your drive chain. However, the worst case scenario is you will need to remove two links. As Detours stated, CSC has promised they will be stocking a 42T C/S sprocket, which will undoubtedly fit the stock drive chain.

If you wish to modify your sprocket carrier, which is the topic of this thread, you can follow the instructions in the first few posts. The JTR1826 sprocket fits the modified sprocket carrier, and it is available in 41T, 42T, and 44T versions.

[peperino]

Alright, gracias for all the awesome info

Cheers

[Riceburner]

Spudrider,

Thanks for all the great info and ideas you've provided. I have gone through this thread several times looking for the link to the Taobao for the sprocket carrier you mention and can't see it, you usually post the links to the items you refer to. So I have gone through the Taobao main site page for the Zongshen NC250, have used it many times now,

https://world.taobao.com/search/sear...cb&abtest=null

and have gone through all 11 pages several times trying to find the carrier

[QUOTE=SpudRider;191666]I ordered my sprocket carrier from Taobao, and it came exactly as shown in the photographs. In addition to the bearing, dust seal, and bushing, it also included a stock, 44T rear sprocket.

Can you share the link to that Taobao carrier you purchased?

With the lack of available stock parts here in Iloilo I need to build my own little warehouse and I want to be able to run that 46 sprocket, going to order that today if I can't find one in the city this morning.

Thanks,

[Riceburner]

Can't find the sprocket carrier from Taobao:

I'm looking in the wrong area aren't I!!! I'm using the NC250 search, that's the engine, silly me, maybe need to try under RX3 search?

Well that hasn't worked yet either...

[SpudRider]

You need to use either of the following search terms.

Zongshen RX3
ZS250GY-3

I can't find the sprocket carrier currently listed at Taobao. Some of these items come and go. Perhaps it will show up again, later.

You can order the JTR811.46 rear sprocket, and wait for it to arrive. After it arrives, you can trim 2mm from each of the radial arms on your current sprocket carrier. However, you might have trouble getting the 46T sprocket to fit on the stock, 110-link drive chain. Therefore, it might be best for you to wait until the sprocket carrier appears again on Taobao. Of course, you could also order a spare sprocket carrier from CSC.

[rjmorel]

Spud, question for you. Would boring out the sprocket hole accomplish the same thing w/o having to buy and modify the carrier? Or is the sprocket to hard to bore out? Or am I missing something else? rj

[SpudRider]

Yes, boring the center hole of the sprocket to a larger diameter would also work. Since you are a machinist, this is not a problem for you. I find it much easier to trim 2mm from each of the six, radial, aluminum arms of the sprocket carrier. After doing this once, I don't need to do it ever again.

[SpudRider]

Originally Posted by Riceburner

Can't find the sprocket carrier from Taobao:

I'm looking in the wrong area aren't I!!! I'm using the NC250 search, that's the engine, silly me, maybe need to try under RX3 search?

Well that hasn't worked yet either...

I would be very surprised if the sprocket carrier for the Zongshen ZS200GY-2 is not identical to the sprocket carrier for the Zongshen RX3. However, I haven't verified this conjecture. The ZS200GY-2 sprocket carrier is readily available for sale at Taobao. However, it includes a size 428, rear sprocket, which can't be used with the RX3 motorcycle.

https://item.taobao.com/item.htm?spm...6-fd7cacd34b59

https://item.taobao.com/item.htm?spm...cket=12#detail

[Riceburner]

SpudRider, rjmorel, I was wondering the same thing about enlarging the sprocket center; I'm not a machinist but do have access to a very good one locally. I was thinking I would have him do the work either way, the removal on the hub or the sprocket. When I get my rear sprocket I'll take it to him and have him tell what he thinks is best. Or, rjmorel, since your a machinist, what do you think?

I was wondering, Spud, if I modify the hub as you did, can you still put an OEM 44 sprocket safely on the hub (not that I think I'd go back to the 44 but...). I remember that on my BMW F650's I had changed to a one tooth smaller C/S and one larger on the rear, made a big difference and I can see it doing the same here, even the two bigger on the rear.

I'm running a 130/80-17 rear tire now (only because it's the closest I can find with my limited availability and choice here) and it's about 3/4" taller than stock so the two additional teeth should really help me.

[Riceburner]

Thanks SpudRider for the info on the ZS200GY-2 carrier, I'll check it out.

[SpudRider]

Originally Posted by Riceburner

...I was wondering, Spud, if I modify the hub as you did, can you still put an OEM 44 sprocket safely on the hub (not that I think I'd go back to the 44 but...)...

No, you can't safely mount the original sprocket on a modified sprocket carrier. However, you can install the JTR1826.44 sprocket on the modified sprocket carrier.

http://www.amazon.com/JT-Sprockets-J.../dp/B001AVQOQW

http://www.jtsprockets.com/catalogue/sprocket/JTR1826



If you buy a spare sprocket carrier, you can mount Zongshen and CSC sprockets on the unmodified sprocket carrier, and mount the other sprockets mentioned in this thread on a modified sprocket carrier.