Zongshen RX3 carbureted version mods & repairs

[Weldangrind]

It's not that hard; whomever removed your jets for cleaning can certainly adjust the pilot mixture screw, and so can you.

Look at your first pic, that shows the carb bowl. Notice how the bowl has a curved section at the front? That is for clearance to the pilot mixture screw. Feel around under there, and you'll find it. The next step is to find some sort of screwdriver bit that will fit in there, and turn it counter-clockwise (while standing on your head) about 1/8 turn. Start the bike and go for a ride.

I'm not actually convinced that the carb is totally clean. The pictures you attached show the bowl and jets removed for cleaning, but not the entire carb. In your third pic, you can see the main jet next to the screws. The main jet screws into the large tube with the o-ring, and the smaller tube to the left is the slow jet. I suspect that the hole the slow jet screws into still has debris in it. The only solution is to remove the carb and carefully clean that passage.

[jezzrite]

Originally Posted by Weldangrind

It's not that hard; whomever removed your jets for cleaning can certainly adjust the pilot mixture screw, and so can you.

Look at your first pic, that shows the carb bowl. Notice how the bowl has a curved section at the front? That is for clearance to the pilot mixture screw. Feel around under there, and you'll find it. The next step is to find some sort of screwdriver bit that will fit in there, and turn it counter-clockwise (while standing on your head) about 1/8 turn. Start the bike and go for a ride.

I'm not actually convinced that the carb is totally clean. The pictures you attached show the bowl and jets removed for cleaning, but not the entire carb. In your third pic, you can see the main jet next to the screws. The main jet screws into the large tube with the o-ring, and the smaller tube to the left is the slow jet. I suspect that the hole the slow jet screws into still has debris in it. The only solution is to remove the carb and carefully clean that passage.

I believed when they cleaned out the aforementioned jet, they also blow the heck out of other jets. But, I might be mistaken, because all I heard was the blowing process, and didn't pay much attention cause I was talking to my dealer by phone.

When I got back from work this evening (went to work with another Chinese bike with no problems so far), I tried to start my bike.

It roared to life with little effort and with just one push of the starter button.

Okay, now I'm confused. Should I just ignore it, since it started flawlessly (at least for now), or should I just proceed with the tune/repair/cleaning of the carb as per your guidance?

The dealer called me and they said that they can fly a mechanic from their other branch to deal with my carb. But still, I have to ride 200km to the dealer's shop.

[Weldangrind]

I'd ride it and monitor for awhile.

[FTEY]

Originally Posted by Weldangrind

I'd ride it and monitor for awhile.

Agree. Continue riding it and see. You'd be surprise that it will improve overtime.

[Adventore]

Just like to give couple updates on my last service. Please note that there are 3 oil filters that you need to clean. The location is as shown in below pictures.







The mechanic just wash the filters with soap and blow dry them. Be careful, these filters has assembly orientation. Do not forget the right way when put them back!

And for the problem of hard to get to neutral, the mechanic changed my clutch spring. I manage to snap a picture of both existing spring and the spring the he put on my bike later for your reference.

The spring on the right of the picture is the original spring. Left is the replacement.


From the picture you will see that the spring that the mechanic replace for me is having lesser number of coils and smaller wire diameter. Changing to softer spring will cause slip clutch problem. Mine happen on first gear when I crank my throttle too much when I slowly release the clutch.

I am going to use it to observe the performance at this moment. My idea is to change to the spring with same compression force with the existing ones but lesser number coil number. This might solve the problem.

[Riceburner]

Ok folks please help. I have the Zongchen / MotorstarZ250R, Philippine version, it's carb powered and mine has had issues from day one. I had the hesitation issues at first from 3500 to 5000 RPM, several trips to the dealer and it went from bad to worse to un-ride-able, with Km per liter down to 13 KPL, (really), since new I have only been getting max 19.6 KPL. Then they got to where it only hesitated/coughed at 4500 to 5000 and 21 KPL.

This happens in all gears and any speed, it's the RPM range, 4500 to 5000.

Thanks to Mororstar's head mechanic in Manila he posted a fix on Facebook and on Saturday 25th the local shop mechanic performed the adjustments, I took a print out for him to read and see. This is his instructions:

Eric Dela Cruz
July 19 at 4:03am

1. Remove the white plastic washer of the carburator jet needle (as shown on attached pics above) to set the fuel in lean condition 2. Set or place the circlip at the topmost notch 3. Adjust the air screw at the 3 full turn clockwise


The bike was much better, felt perfect and I was happy on my 35 Km ride home. The next morning going to meet friends for a long ride at about 20 km into it I noticed the same hesitated/coughed at the 4500 - 5000; what???

We went on a 350 KM ride and these guys ride fast, fast for here in Iloilo and Panay road conditions, I'd say we were averaging 80-90 KPH and sections of 120 many times; I hit a top sustained speed (indicated) 145 KPH (90 MPH), that's what I made it too anyway. My average KM per Liter was 25.6 (all indicated as per the stock speedo and Odometer and we know they aren't accurate but close enough for now). I was surprised when I calculated this, thought it would be worse.

The entire trip I had that constant RPM problem and that makes riding very annoying and even possibly dangerous given you can't just turn the throttler and accelerate without hitting that RPM range, just not right.

I did tell the local mechanic that I understand the engine and carb must be hot when adjusting PMS and of course he didn't listen to me, did it all on a cold engine.

I want to like this bike but as of right now I can't say I'd purchase another one or recommend it to my friends. I need to get the carb under control and redo the seat again, terrible seat for me. I know the details can be corrected and I'm sure I will end up enjoying at some time.

So, anybody got other ideas here?

[Jay In Milpitas]

For those who have the bikes with carb, I would like to point out the sediment (dirt) trap you have on your fuel valve. The bottom of the valve unit has a cup or bowl that takes a 10mm wrench. The gas goes from the tank down in to the trap, then back up through a filter screen before going out the hose.

That bowl and screen may need to be cleaned often if gas stations have dirt and water in the storage. Just unscrew the cup while holding a small container under it to catch what comes out. You may see some water in the bottom and also dirt or rust. Just dump it all out. Use a mirror or turn your head to look inside the valve for the screen. It is usually just held up with a rubber o ring. Clean it if you need to. While the cup is off, no fuel should run out of the valve. If it does there is a problem.

When you put the cup back, do not make it very tight. It only needs to seal against the o ring. Adding a filter in the hose will also help to keep the dirt demons out of the little holes in the carb jets, but the valve is the first defense against carb problems.

Happy riding, Jay.

[Keribang]

Bro Adventore & FTEY,

I'm planning to get this KTNS RS3 here in Malaysia but a bit apprehensive after reading these posts on the problems you guys have with the carburetor. How're your bikes running now? Are they better? Can the carb be replaced/upgraded to a better carb?

Thanks.

[SpudRider]

Welcome to these forums; we are glad you joined us.

[Jay In Milpitas]

Hello Keribang.

So far it seems that most of the carburetor problems have been because of some mechanics that are not good at working on them. There is no magic, but things must be done right.

Riceburner had a problem that was getting worse each time a *head mechanic* worked on his bike. Some of his friends came over and made everything right in a short time just by doing the right cleaning and adjustments.

How is your skill with mechanical things?

[Keribang]

Originally Posted by Jay In Milpitas

Hello Keribang.

So far it seems that most of the carburetor problems have been because of some mechanics that are not good at working on them. There is no magic, but things must be done right.

Riceburner had a problem that was getting worse each time a *head mechanic* worked on his bike. Some of his friends came over and made everything right in a short time just by doing the right cleaning and adjustments.

How is your skill with mechanical things?

Hi Jay,

I would say my mech skills are err... intermediate. I've a mech eng background & at one time owned an auto workshop. My concern is not really taking apart a carb or tuning it - I've done that before though not an expert at it. It is more about if the carb on this bike has a possibility of not being design properly from the start. I read earlier posts that the main jet had to be changed 1 size up to resolve a problem and that points to design problems to me.

But you're right, it is not rocket science to clean & tune a carb, and may be able to just do it myself. I shall keep this bike in consideration for my search. I'm going back to riding after many, many years off the bike & doesn't want to start on big cc bikes until I get my confidence and basic riding skills back in order.

Thank you very for the feedback.

[SpudRider]

I'm sure the carburetor is excellent. I own two Zongshen motorcycles. My 2006 Zongshen ZS200GY-2 has a carburetor. It is a Teikei MV28, which is virtually identical to the Teikei MV28 installed on the currently manufactured, Yamaha TW200 motorcycles. The fundamental difference is the Zongshen carburetor employs one throttle cable, and the Yamaha carburetor employs two throttle cables.

Zongshen does not put bad parts on motorcycles, and Zongshen is especially diligent to put good parts on its engines. It is very common for carburetors on new motorcycles to need jet changes.

I agree with Jay. The problems seem to be caused by poor customer support, especially poor mechanics. If you need good customer support, you probably want to consider buying another motorcycle. However, if you plan on doing most of your own maintenance, and are able to properly jet the carburetor, et cetera, I think the Zongshen RX3 will be a good choice.

[Jay In Milpitas]

Originally Posted by Keribang

Hi Jay,

It is more about if the carb on this bike has a possibility of not being design properly from the start. I read earlier posts that the main jet had to be changed 1 size up to resolve a problem and that points to design problems to me.


Thank you very for the feedback.

From my experience of many years and many makes of motorcycle, a carb may need to have jetting changed depending on what altitude it is at. I have changed jets on bikes near sea level which were jetted for the original destination of more than 1kM above sea level.

Yes, there have been a few postings on internet about RX3 carb problems. I wonder how many hundred or thousand are running with no problems?

I like that you put much consideration in to a product before buying. I wish you luck with your decision.

[Riceburner]

I have to say that I think the bike is basically a great bike, seems to be built well and though I have had this nagging carb problem my biggest issue isn't "the bike" but really the dealer and their lack of customer service and ability.

After my friends and I re-repaired the carb we found a lot of Three Bond gasket sealer and after installation I noticed fuel leaking from the bowl, upon removal again I noticed a gauge in the carb body on the mating surface for the O-ring. I asked the dealer to replace the carb under warranty and due to their head mechanics's lack of care. So far a bunch of run around and picture taking that has nothing to do with the carb.

I have my bike taken apart right now, had some parts painted and repainting the crash bars. I'm sure the stock/OEM paint is good for dryer locations but I'm a quarter mile or less from the beach and then it rains here a lot; I noticed a few spots of rust a the weld points on the crash bars, head light/dash cluster and rear luggage carriers so I had them repainted with a Zinc base and epoxy primer. Might slow the rust but never stop it. Everything here either rusts or molds... even me.

In having the bike torn down so much, I can see they have done a generally good job of build. I'm still openly positive towards the bike and look forward to putting miles on it.

One thing to look for at least on the carb models, (I'm sure the EFI wiring loom is a bit different but check anyway). The wire loom runs along the left inside frame rail, there is a cross bar that the fuel tank is supported by and it rests on two rubber half round bumpers; the wire loom was being pinched between the rubber bumper and the tank, could cause potential trouble up the road. I noticed this at the first carb adjustment and have tried to pull it into a better location.

Riceburner

[Jay In Milpitas]

Originally Posted by Riceburner

One thing to look for at least on the carb models, (I'm sure the EFI wiring loom is a bit different but check anyway). The wire loom runs along the left inside frame rail, there is a cross bar that the fuel tank is supported by and it rests on two rubber half round bumpers; the wire loom was being pinched between the rubber bumper and the tank, could cause potential trouble up the road. I noticed this at the first carb adjustment and have tried to pull it into a better location.

Riceburner

Right there is a great example of little things that can become big problems. Thanks for sharing it, I know I'll be looking a little closer at mine.