Carb hesitates/coughs at the 4500 - 5000

[Riceburner]

Ok folks please help. I posted this in the carbureted version mods & repairs but haven't heard from any of you smart people.

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]

Hello Rice.

Is there any other rider that would trade carbs with you for a test? If carbs are traded and your bike still has the hesitation, then something else is at fault.

Good luck.

[Riceburner]

Hello Jay, good idea but there are only two bikes on Island, the other fellow had his carb changed out to a slid style rather than the OEM diaphragm, I haven't had a chance to chat with him and swap bikes for a test ride. I hate the idea of having to purchase a new carb.

[Jay In Milpitas]

Hi Riceburner.

I just read your post again and overlooked something before.
If the problem is always 4500-5000 rpm at any speed and in all gears, then it may not be the carb at all.

For example, if in gear 3 at low rpm and you open to full throttle, then it is only using the Main jet, so as it goes to 45-5000 range, the only thing changing is electronics telling the coil to fire the spark plug. Having the carb work done did not change it and made your fuel mileage worse.

Hopes this helps your dealer to find the problem.

[Riceburner]

Jay, thanks for the idea. Have any idea as to what area of the electronics I should be looking at? How to fault find and repair?

I'll take note of this to the dealer next week when I go see them (again).

Riceburrner

[humanbeing]

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Mechanic & primitive tool series
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[Riceburner]

humanbeing, thanks for the links: Mechanic & primitive tool series, those home made tools are cool...

I have two of what are supposed to be the best mechanics coming over to the house this morning, hopefully we can get this thing resolved and I can begin to enjoy what should be a great bike.

Riceburner

[Riceburner]

I have been very frustrated since I took delivery of this bike, it hasn't run properly from the start. Since it's under warranty I felt if there is a "problem" the dealer should correct what ever it is and if need replace what ever needs under the warranty program; well forget that idea from now on, I'll just follow SpudRider's instructions and order stuff from China via Taobao and do it myself.

I have been wanting to “like” this bike, I feel it has potential and has many good features.

So, I have taken the bike to the dealer I think it's four times now and even took special instructions given by the companies “head mechanic” in Manila and they brought what is supposed to be their head mechanic here in Panay to the shop and we went over the instructions, all was supposed to be good.

As I mentioned the bike kept getting worse and lately would not run at all, not over 17 KPH.

I got two really good mechanics to come to the house, I have no way to take the bike to them and it's about 35 kilometers between us. They work on my friends bikes and have done work on my Yamaha YBR125G.

So what we find... the dealer “head mechanic” did not follow instructions and poor workmanship.

The manifold bolts were loose, not even snug. They applied Three Bond gasket sealer to the O-ring and surface but didn't tighten the bolts, figure air sucking around the manifold.

Open the carb and the float is set way too high, almost to max position. They did adjust the clip in the needle per instructions. But they also used Three bond on the float bowl gasket and that's a no-no. There was extra Three Bond floating in the bowl and some water (???).

They set the PMS to five full turns out not the 2.5 to 3 I had instructed.

So my friends corrected the issues and set everything to the proper specs, the bike ran great. Superb get-up-and-go; responsive and no hesitation at the 4,500 /5000 range. No hesitation at all. It was raining when we finished the work so first ride was only a few hundred feet. This morning I took it for a 10 Km ride through all the gears, speeds and RPM range. It is responsive all over. I am able to lug the engine way down in third and second gear, it will pull out from there without the hesitation I had before, actually it wouldn't let me lug the engine, it would just die. The ride this morning wasn't long and a bit of congestion on the road ahead so I only topped out at 114 KPH but all felt very good, I like it.

We were discussing why it ran good after the last dealer adjustments for the first 50 or so kilometers and then started running bad, seems that maybe the loose manifold bolts did just that, got a bit looser during the time and then with the five turns on the PMS just not good.

I know the carb is no “black magic” device, it's just a basic vacuum carb and this model has been around a long time on many different brands of bikes. But as mentioned by some other folks the problem could be electrical related and so in part why I wanted the dealer to take care of the problem. They just don't have the skill and don't listen to directions and defiantly don't possess the tools required to do many tasks; I wouldn't let them adjust the valves even if they thought they need to be adjusted. When I asked them about valve adjustment they were adamant that it's self adjusting; SO...

This carb issue isn't just my bike, it's been documented many times and from what I've read, brought to Zingshen's attention; it's not overly common but it's not “un-common”. I think this is an issue of Zongshen's quality control. I don't know how they run the carb acceptance from the supplier issue, maybe expecting they are all set up and adjusted properly from the supplier or if they are supposed to set up after install; I've got no idea but there is certainly a problem some where in the process and it would do them and even their other dealers, like CSC a big favor to check and correct this issue of carb supplied bikes. It reflects bad on all Zongshen models, carb or FI; USA, Philippines, Australia or Russian.

I'd like to think that if the US model RX3 were carb powered, that CSC would be addressing the issue, they seem very involved in issues like this related to the RX3. I've mentioned someplace that you US buyers are lucky to have such an involved and customer service related dealer, something we don't have here in the Philippines .

So by now your probably sitting on the edge of your seat and asking about the water???

We took off the tank, almost full, more than 12 liters, and drain the gas; OMG... a lot of water in the first coke bottle, right off and a lot of water in all the bottles (I forgot to take pictures), I mean “a lot of water”. This isn't from the gas station, way too much.

So you say the vent hose was plugged right; well no, it's clear. The gas cap was secured and locked in place.

I mentioned that in the last week the bike wouldn't run at all. Along with the carb issues stuffing water through the carb gives very bad performance (clean gas but...).

It has been raining very hard the last four weeks and especially two weeks ago (another Typhoon). I live in an area that gets something like 30 plus Typhoons a year and I read somewhere more than 77 inches of rain a year. I don't have a formal garage (do miss my big old Las Vegas garage), the bike stays under the eves of the house normally with a water proof bike cover but... Working on the bike I had it under the vine covered lattice work and had the other bike cover (not “rain proof”, resistant but) on it that rainy week. Now I've had that bike cover, not water proof and used it for three years; it's been covering the Yamaha and many times in the heavy rain in that same location as the Z250R(carb version) / (RX3, FI) was sitting.

The only answer I can come up with is the rain seeps in around the fuel cap, supposed to flow out the drain tube but instead seeped in around the actual fuller cap seal. I don't think the filler cap seal seats properly. I don't think any water should seep in through the seal . Now if any of you have a different opinion or other ideas please share.

I'm a bit concerned that if the seal isn't seated fully that during a long ride in those torrential down pours the water could seep into the tank, sometimes the bike will have to sit out in the rain for sometime before I move on; what do you think?

Why would I ride in a Typhoon down pour you might ask??? I work with a nonprofit group, Medical Mission Matters (www.medicalmissionmatters.org ), we provide free life changing surgeries to the poorest children with Cleft Lip and/or Cleft Palate. I ride way out into the Province's (back country, boonies, outback) and find these kids, deliver free vitamins and when prescribed, free medications; and if their scheduled surgery is close and they need the vitamins or medication and even free travel money, it doesn't matter if it's raining, sunny or torrential down pour, I'm on the road delivering. I have done that more times than I can count, put on the full rain gear before I leave the house, ride 200 / 300 Km round trip and not take off the gear until I'm home under the patio (I love helping the kids and meeting these people way out in the homes) and so that's why I'd ride in a Typhoon .

If the rain will stop I can install my bar risers and the headlight modulator and relays. I have been working on the seat, lowered the base about a half inch, added all new foam (the best I can get here, not perfect but the best I can get) and have reshaped it to be more of a saddle/dish at the back and more level across the seating area. I think I might like a bit more foam under my butt and will add a half inch prior to taking it to the upholstery shop on Monday. With the reshaped seat and bar risers I'm thinking I should be more “sit up and beg” and more comfortable on the lower back and of course, better comfort and control standing when off road (about 30% of my total riding). I actually expect to redo the seat again after a few thousand kilometers or so. I'd like to find a good metal worker and maybe even have an all new seat pan made, that would give me a happy butt.

Thanks for all the help and ideas shared with me so far, much appreciated.


Riceburner

[detours]

Good for you, working with such a cool group! And congrats on fixing your own carb issues! Sucks that their 'master mechanic' can't work on a carb or recognize water in the tank and doesn't know to tighten the bolts when he's done.

About the water in your tank, I've noticed my gas cap needs a very firm push to fully seat. And I mean VERY firm. I have to push until I hear a second click. Then I know it's in. I wonder if yours is the same?

[SpudRider]

Congratulations; I'm glad your bike is now running well.

X2 on the fuel cap. It requires a very firm push to secure the fuel cap in a level locked position.

[Jay In Milpitas]

That is great news, RiceBurner!

I suggested the electrics giving problems only because I made the mistake of assuming the mechanic that worked on you bike was a,,,,,,,, mechanic. From the sound of it, I don't think I would trust him to roll a lumpia.

Happy & safe riding, Jay.

[Riceburner]

Well as I have mentioned in the past I have had trouble with my carb from day one and in-spite of many attempts from the dealer Motorstar, they were not able to correct it and at the last attempt they even damaged the carb body, the fuel bowl gasket area had a gouge in it so the O-ring would not seal.

I did get it fixed myself but was not happy that the dealers mechanic's had damaged the carb and on Sept. 9th I delivered a demand letter giving them 10 days to replace my carb under warranty and stated I would do the swap myself. Since I had not heard from the dealer in respect to this I figured they were just blowing me off and had no intention of taking care of me. I suffer from an inherent lack of trust in my dealer MSS Cycle Trading and Motorstar. I was looking at purchasing a replacement one.

Well I was surprised yesterday morning Sept. 22nd when I got a text saying the dealer was sending their head mechanic to my house (21 Km from the city) with a replacement carb, under warranty.

Randy, the mechanic showed me the inherent problem with many of the OEM RX3 carb's, this is a Keima brand, I think the model number is PD36J but I think it's a 32mm. The problem is with the Throttle Slide and the chamber; on my carb there is obvious uneven wear from resistance and contact of the slide on the chamber wall, (I tried to post pictures of this but I seem to be picture posting challenged).Wait, maybe I figured it out by mistake and with Weldangrid's directions...

Randy said he just finished two weeks in Manila at the headquarters going through intense training on the RX3 so now he is qualified on the bike. I asked if this carb issue is being addressed by Zongshen and he indicated it is. It's not an uncommon problem and not excessively common but just enough around the world to be apparent.

Randy also made the adjustment as per Motorstar's Head Mechanic in Manila, Eric Dela Cruz, as he posted on Facebook:

Eric Dela CruzSorry sirRobin Haywoodfor late reply, it was that im not apparently always online this past few days for some reasons,,, some of our customers here in manila also experiencing same trouble as you encountered with your bike like idle hesitations, or...See More
Like·Reply·1·7 hrs

Eric Dela Cruz1. 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
Like·Reply·7 hrs

Eric Dela Cruzhttps://www.facebook.com/groups/412630818887109/permalink/486978228119034/

I have only put about 60 Km on it but it seems to be running perfectly so far, no hesatation at any speed or RPM and she “get's up and goes”. Wont feel really comfortable until I get more seat time and then we'll see.

So now I have a slightly different attitude towards my dealer MSS Cycle Trading in Iloilo City and Motorstar. They did end up coming through and doing the “right” thing and provided good customer service, thanks you.








I hope this “fix it” can help others with the hesitation and cough of the carb models, it's fixable and maybe you need a replacement “under warranty” carb.

[Adjuster]

Glad to hear your getting squared away.


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[SpudRider]

I'm glad to hear Motostar honored the warranty, and replaced your carburetor. Thanks for posting the update.