Zongshen RX3 Rally Build Questions

[MotoMatsalleh]

Hey everyone!

I'm a hobby rider and vlogger based in Malaysia. I've recently done a full review series for the RX3 (carb version sold in Malaysia)

Review series -https://www.youtube.com/watch?v=Fh4z9pcRmjw&list=PLKKWqk_DAh7AAUf13H1pGXYa VkvYkqFPQ

I have a close relationship with the Zongshen distributor here in Malaysia and I've worked out a deal that should make for a fun bike build. I'm going to do an RX3 Rally Build. Basically, the dealer here is supplying me a stock carbed RX3, any OEM parts, and a mechanic.

I supply aftermarked parts and do a build series on my Youtube and Facebook pages to promote the bike and modifications to the existing owners group.

Youtube -http://shorturl.at/ilowL
Facebook -https://www.facebook.com/motomatsalleh/

So, I like this bike especially for Malaysia. I always do tons of miles on the highway and always find trails. Not much rock hopping, think sticky jungle mud and slippery steep decents.

I am not having to buy the bike or pay a mechanic, so I am willing to put cash into the bike to make it fun. I wanted to get this boards opinion on mods so I can prioritize and build on what you guys already know. Please give any and all suggestions EXCEPT please don't tell me to start with a different bike..I already know thats the "best choice" ha ha.

Front Suspention - What are the options here?
Rear suspension - anything other than the progressive shock sold by CSC available?

I've already got a 21" fron wheel from an RX3 racing bike and a spoke 17" rear

Airbox mods?

Any options for pumper carbs?

Is the big bore worth it? If so, got any carb and jet suggestions for sea level and 90 degrees F?

Best ways to cut weight?

New seat options?

Who's found an aftermarket exhaust that's less restrictive and more Brappy?

Lighting and electrical?

Fire away guys.

[Working_ZS]

I'm not aware of any heavily modified RX3's in the US, apart from those people who have installed big bore kits. Many of them experience issues with the bike running too lean at higher RPM's, and there is no way to correct it short of a new fuel injection map being flashed into the ECU. That, unfortunately, has not been figured out by anybody; or if they have, they have not posted about it. You would probably have better luck with your RX3, as it is carbureted and can be re-jetted for the increased displacement.

To date, CSC's Progressive shock is the only option for suspension mods, and that is only for the rear. There has been nothing developed for the front, to my knowledge.

In regards to weight reduction, you could look at stripping of the cases and mounting racks, as well as the crash bars. It is also possible to replace the steel hoops of the wheels with aluminum ones, you can read about that here:

http://www.chinariders.net/showthread.php?t=17732

and here:

http://www.chinariders.net/showthread.php?t=14974

Another thing to try is fabricating a new side stand, making it out of hollow tubing instead of solid steel, like the OEM one.

There are no aftermarket exhausts available in the US, but I think AKT Motos in Columbia makes one. I remember CSC brought one in to the US for evaluation, if I remember correctly. I don't believe that there was any meaningful difference, so they opted not to import them. A few people have put on Akropovic slip on mufflers; check YouTube for videos.

For the headlight, you need to replace the 35W H1 with a 40 watt LED bulb, preferably one with a low beam cut off. This is assuming that you have a 2015 1/2 US style headlight housing. If your RX3 has the older style, with the blue running light beneath the main headlight bulb, the swap will not be as effective. It will still produce way more lumens than the stock bulb, but the dispersal pattern is not as even as the later US style. If you decide to retain the crash bars, definitely fit auxiliary lights. I use a cheap set of Auxbeam 18W flood lights on mine, they work well for me riding at night.

Your project sounds interesting, definitely keep us posted on what you do with it.

[MotoMatsalleh]

Thanks for the feedback and links. I also have a handful of nc450 motors from the rx4. Basically the company brought in test models but decided not to sell the rx4. Now they are collecting dust and can never be registered.

Is the bolt pattern the same for the engine mounts? How much taller is the nc450 motor?

[franque]

Hey, so I've got a couple of questions for you, and potentially a couple of answers. Firstly, are you planning on actually rallying the bike, or is this more of a styling exercise? Secondly, are you restricted/limited to only Zongshen OEM parts, or are you relatively free with regards to what you'd like to use?

As for the NC450 motors, no one that I know of has attempted a swap, it might be up to you to make the measurements and determine that for yourself (thought please share what you find, if that's what you end up doing!), I'm not even sure as to the differences in height, etc.

For the NC250 motors, I've heard a lot of good things about the big bore kit, but would suggest you do the smaller (286?) kit, as I believe that I recall hearing reliability issues with the true 300. I don't think you'll need to change anything with the cooling system, it should be good to go.

If you're looking for some more performance, there's an American company, Thumper Racing, who will be making cams for these. Contact Navin on advrider if you want more details, here's a link to what he was saying, last post on the page: https://advrider.com/f/threads/gpx-f...317003/page-29

If you're actually wanting to rally it, I would look at getting some front suspension off of a 250/450 MX bike and paying someone to tune the suspension to the bike. Fork swaps are not that challenging, though they seem intimidating, you'll basically need to make sure that you can find bearings that fit the steering stem and the steering neck on the bike; it might involve some work on a lathe, and possibly making a steering stem to suit your triple clamps and steering neck length. You might also need custom triple clamps if stuff is in the way, but trust me, any properly tuned MX suspension from the last 20 or so years will be a massive upgrade in suspension for the RX3.

The biggest thing, if actually racing it, will be to make sure that it is as light as possible, has sufficient fuel capacity, and is strong enough to do what you need to do; I imagine that the RX3's frame is mild steel, for weight and strength purposes, it might be a good idea to get a chromoly (4130) frame made for it, or consider something like a Kayo T6 for a starting basis and build up, as I think you'll need to strip a lot of things to make an RX3 functional for a rally bike.

[MotoMatsalleh]

Originally Posted by franque

Hey, so I've got a couple of questions for you, and potentially a couple of answers. Firstly, are you planning on actually rallying the bike, or is this more of a styling exercise? Secondly, are you restricted/limited to only Zongshen OEM parts, or are you relatively free with regards to what you'd like to use?

As for the NC450 motors, no one that I know of has attempted a swap, it might be up to you to make the measurements and determine that for yourself (thought please share what you find, if that's what you end up doing!), I'm not even sure as to the differences in height, etc.

For the NC250 motors, I've heard a lot of good things about the big bore kit, but would suggest you do the smaller (286?) kit, as I believe that I recall hearing reliability issues with the true 300. I don't think you'll need to change anything with the cooling system, it should be good to go.

If you're looking for some more performance, there's an American company, Thumper Racing, who will be making cams for these. Contact Navin on advrider if you want more details, here's a link to what he was saying, last post on the page: https://advrider.com/f/threads/gpx-f...317003/page-29

If you're actually wanting to rally it, I would look at getting some front suspension off of a 250/450 MX bike and paying someone to tune the suspension to the bike. Fork swaps are not that challenging, though they seem intimidating, you'll basically need to make sure that you can find bearings that fit the steering stem and the steering neck on the bike; it might involve some work on a lathe, and possibly making a steering stem to suit your triple clamps and steering neck length. You might also need custom triple clamps if stuff is in the way, but trust me, any properly tuned MX suspension from the last 20 or so years will be a massive upgrade in suspension for the RX3.

The biggest thing, if actually racing it, will be to make sure that it is as light as possible, has sufficient fuel capacity, and is strong enough to do what you need to do; I imagine that the RX3's frame is mild steel, for weight and strength purposes, it might be a good idea to get a chromoly (4130) frame made for it, or consider something like a Kayo T6 for a starting basis and build up, as I think you'll need to strip a lot of things to make an RX3 functional for a rally bike.

Thanks for the reply, let me answer your questions

1. I am planning on rallying the bike, but more amateur type stuff. I'm wanting to make strides in both form and function.

2. I can use any parts to modify the bike. The company here will pay for any OEM parts from any year the RX3 if I need them. Aftermarket comes out of my budjet.

3. I'll measure the RX3 and the nc450..worth a look because the motor would be free for me. I read it's slightly taller and the front sproket would be about a 1/3 inch higher than the nc250, but mounting bolt pattern is the same. Would sproket hight be a big issue?

4. I've thought about a straight up suspension swap, though it really does intimidate me. Mechanics here are not always creative and outside the box (like a pro machine shop). Any ideas for forks that might be the least amount of work? If i go this route, I could just have racetech build them up since they would be a common size...Thoughts?

5. Thanks for the tip on the cam!

6. As for the frame.....sounds fantastic...I have no earthly idea how to go about ordering a custom frame. Can you point me in the right direction? It would make it a totally different bike which would be really cool, though if I could have one made in Asia I'm sure it would cost a lot less.

Thanks so much for the feedback, I'm willing to consider anything, and my budjet might be more than most can afford because 1. the bike is free 2. labor is free 3. I make a little money back when I do videos

I'd love to consider every angle before I make a plan.

[franque]

How much offroad experience do you have, and where are you planning on rallying it? I'm not sure what sort of rallys are available in Malaysia? For better form/function for this bike, you'll need to make it lighter if you want to race it.

Sprocket height shouldn't be a big issue, it depends on the size of the sprockets/how much space you have to work with.

For the fork swap, just compare the size of the bearings vs the steering stem size on the front end you want to swap on. If it's easier, just get another front end off of something, remove the front end on the RX3, and compare, so you can understand what I'm talking about (even something that you wouldn't consider swapping, just to see how things vary in that context).

Any forks that would be worth getting probably won't be 'easy' to change out, especially since they're USD forks, with conventional forks, usually it was just a matter of the stanchion diameter, but with USD fork tube, they're usually two different diameters, and there's usually a taper involved, so again, you just need to get a set of forks.

This video explains pretty well how a front end would be swapped:


You'll need to measure your bearings/races to determine what can go in (you'll need to know steering head length, too, when you're trying to make it fit all together). https://simplybearings.co.uk/shop/In...972/index.html

Once you find out your bearing dimensions (because Zongshen won't be on this site), find a bike with the same bearing dimensions, and compare that to the bike whose forks you have. https://www.allballsracing.com/forkconversion

Just a recommendation, I've heard good things about KYB SSS forks, which were used on a lot of post 2000 Yamaha YZ/WR bikes. Racetech could build them for you, but I'd suggest learning some of how to do that yourself, as rallying is expensive if you don't do it yourself, and depending on the skills/experience of your mechanic, dealing with something like a relatively modern MX fork will be an entirely different universe compared to what the average Malaysian would be riding around on.

I would look on some Australian forums, as they're closer to you, and they like to rally stuff. I'm not sure who you could get to make a frame in Malaysia, Australia might be a better bet, but you might also have to look into how difficult it would be to import something like that into your country. That can be very difficult/impossible depending on the country. I know of a guy who does custom frames for rally bikes in Aus, but since you'd probably have to figure out yourself (or pay him to do this) to design the frame, it might make more sense to start with a bike that is suited to rally.

Potentially, if you know of anyone who fabricates cages for racecars, you could get them to duplicate the frame out of better steel in country. That's where I'd look.

[MotoMatsalleh]

Hey everyone, here's an update video for the Rx3 build!

https://m.facebook.com/story.php?sto...66931390613929