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Subject: "Kymco ZX-50 idle problem, need assistance!" Archived thread - Read only
 
 
Conferences > International New Scooter BBS > Topic #3736
Reading Topic #3736

MDVZ06
Member since Sep-28-05
2 posts
Sep-28-05, 08:30 PM (EDT)
 
"Kymco ZX-50 idle problem, need assistance!"
 
   Hi, I'm a new member here & I need some assistance. My girlfriend has a '04 Kymco ZX-50. It hasn't been used for at least 6 months since she got a new car & had no more need to use the scooter; hence it sat up and wasn't used. She wants to sell it so I got it, replaced the battery & tried to crank it up (it ran great before she stopped using it). It wouldn't crank. Figuring the carb probably was gunked up from varnish due to bad gas, I replaced the carb with a new one, made sure all the lines were good & unclogged & replaced the NGK plug (yes, I also removed the gas tank, drained it & put in new gas). Now it'll crank & try to run or it'll crank & then bog & shut off. Either way, it's very hard to crank. I can get it to crank & run, but after several minutes of running, it'll just bog down. I'm at my wits end tryin to get this thing to run. I would appreciate any suggestions or a point in the right direction! Could the carb need adjustment? If so, how do I go about finding which screws on the carb control what. I tried to find a service manual for this year ZX-50, but that seems to be impossible to find!

BTW, another problem is that the dealership that she bought this scooter from (Savannah Scooters) is now out of business. The next closest Kymco dealer is in Atlanta, 250 miles away, so it would be tough to take it to a dealer......


 

 
adminadmin
Member since May-28-02
1518 posts
Sep-29-05, 09:06 AM (EDT)
 
1. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #0
 
   Will is start and rev with quickstart sprayed in the aircleaner?


 
MDVZ06
unregistered user
Sep-29-05, 11:03 AM (EDT)
 
3. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #1
 
   >Will is start and rev with quickstart sprayed in the
>aircleaner?

I haven't tried that yet, but if you remove the air cleaner assembly & partially restrict the carb intake with a couple of fingers, it'll try to fire. I'll get some quickstart today & try that.


 
AGENT TOP END
Member since May-2-03
952 posts
Sep-29-05, 09:42 AM (EDT)
 
2. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #0
 
   drop the bowl and take out the jets. You need to run wire, very small thru all the holes in both jets. I believe that the idle mixture screw, the one that is inset, needs to be turned out 3/4 to 1 1/4 from the bottom.

Your problem is most likely in the jets, the small on is the idle



 
MDVZ06
unregistered user
Sep-29-05, 11:06 AM (EDT)
 
4. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #2
 
   >drop the bowl and take out the jets. You need to run wire,
>very small thru all the holes in both jets. I believe that
>the idle mixture screw, the one that is inset, needs to be
>turned out 3/4 to 1 1/4 from the bottom.
>
>Your problem is most likely in the jets, the small on is the
>idle

Is it possible that a brand new carb has restricted jets? I'll check this out as well. Thanks for the replies!!


 
MDVZ06
unregistered user
Sep-29-05, 11:19 AM (EDT)
 
5. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #4
 
   I just spoke with the Kymco dealer in Atlanta & they told me that it sounded like a petcock problem to them. If you remove the main gas line from the carb & turn the motor over, there is no gas flow.


 
MDVZ06
unregistered user
Sep-29-05, 04:03 PM (EDT)
 
6. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #2
 
   I removed the gas tank & removed the petcock. The screen was clean with no obstruction. Put it back together & back on the bike. The problem is that for some reason when you are cranking the motor, there isn't vaccum being pulled to open the petcock valve so the gas will flow. When I remove the smaller rubber vacuum line & suck on it to pull enough vacuum, the gas flows freely thru the line; however, when I do this with the gas line attached to the carb, the motor will not fire. Now it won't fire at all. Also, with both lines on the carb, if I restrict the carb inlet with both fingers while cranking the motor, I get gas flow thru the carb, but only if it's restricted. I tried putting the breather back on & testing it & gas still won't flow. Something's definitely not right. & yes, I checked the vacuum line to see if there was a leak & there isn't. I think that I have 2 problems here: no gas flow & and a non-firing ignition. What controls the vacuum in relation to the carb, because it's not getting any or enough to open the petcock valve.


 
MDVZ06
unregistered user
Sep-29-05, 05:22 PM (EDT)
 
7. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #6
 
   I removed the spark plug to see if I was getting any spark & there is none. I tried a different plug & there was a very weak spark. Sounds like the ignition module is bad. Where's the best place other than a dealer to locate one of these? Suggestions?


 
Brooke
Member since Jun-3-02
2807 posts
Sep-29-05, 05:45 PM (EDT)
 
8. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #6
 
   I'd imagine that you are low on compression, which equal suction when the piston is traveling the other way. This could be due to a hole in the piston or faulty reed block. But it's hard to say for sure. Are you using the electric start or kick start? If you are using the electric start, one of the brakes must be held in to get spark. I'm not sure if it has to be the rear or if it could be either. Sometimes it's required for kick start as well but not usually. The question I don't see answered would be to ask if you had the vaccuum hose hooked up to the engine and the fuel tap and then tried to kick it over, or use electric start, does gas come out. Do this with and without your fingers over the mouth of the carb. If none comes out when you just kick it over, then you have either a hole in your piston or a faulty fuel tap that requires too much suction to open the valve. It should take very little suction, way less than you'd produce by mouth usually. If you have a hole in your piston there's not enough compression (suction on the other side of the piston) to pull the fuel valve open. If you have a compression test gauge you should check that. You could also check your reeds. If they aren't opening then none of that suction is making it up past them and not to the valve.

As for the spark, if it worked with one plug but not another, I'd suspect the plug or possibly the cap and/or wire. Make sure the cap is in good shape and connected well to the wire and the same for the wire at the coil. (and don't forget about the brake lever thing) But the cdi on the ZX I seem to remember hearing something about them. You can likely mail order them from any kymco dealer. I'd suggest Scooterville in MN (scootervilleMN.com) if you don't have anyone local. Just cuz I know bob's a good guy but most dealers are good enough to order a part for you and mail it without overcharging. You could try Moped Hospital as well. maybe they have a good used spare. I wouldn't expect giant blue sparks though. scooter sparks are notoriously small (yet effective enough).

Having 2 problems sucks for diagnosis. Take one at a time. Start with fuel. When you kick it over (no hand in front of the carb), with the vac line hooked up on both ends, gas should come pouring out of the fuel line in gushes and stops. Keep a bucket handy for waste gas. If it doesn't do this it could be 1) compression (suction), 2)reeds not opening, 3) fuel valve not opening correctly. Check in that order as that is the least expensive order to test (but not neccessarily remedy). After you've resolved this issue, THEN move on to spark. First, use a new plug. Second, check the cap to plug connection. Some plug caps require you to remove the little silver tip of the plug. some clip on it. Then make sure the plug is into the wire, and then the wire into the CDI. If all those are in place and you don't get spark, It's probably your CDI (assuming the key is turned on, the switch set to run and a brake lever pulled in). If that doesn't fix it. Look to the stator for a bad coil. The Kymco service manual should have a test for that with a multimeter but I'm not 100% on that.


 
MDVZ06
unregistered user
Sep-29-05, 06:24 PM (EDT)
 
9. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #8
 
   Yes, the brake is engaged. If not, the electric starter won't work & yes, the kill switch is in the run position! I've tried to crank with the kick start & still nothing. Yesterday this thing was trying very hard to start & was firing; in fact it would crank. It just wouldn't run for very long. Today, nothing. I've tried 3 new NGK plugs and an autolite. I removed the plug from the head & grounded it to see if it would fire. None of the NGKs would fire. The autolite would spark, but very weak and intermittent. I doubt that there's a hole in the piston being as how it was running yesterday. It would fire & crank, but due to the fuel delivery issue, it would bog out.

Yes, I unplugged the gas line from the carb & tried to start with the electric start & no gas would flow. Only if I removed the vacuum line from the carb and manually applied vacuum. Then gas would flow freely.
If you leave both lines hooked up to the carb, spin the starter and cover the carb intake with several fingers, gas then flows freely. So when the carb is restricted, there's enough vacuum to open the petcock valve and for the gas to flow into the carb like it should.

As for the spark, the cap is attached very well to the top of the plug. There is no play at all.

I'm going to order a new petcock valve & a new (or used if I can locate one) CDI box. You're right, this sucks balls. I believe it when I hear that Kymco CDI boxes are crap. Yesterday it was fine & today it goes south! Thanks for the reply & the suggestions. Anymore are welcome!


 
Brooke
unregistered user
Sep-29-05, 06:48 PM (EDT)
 
10. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #9
 
   I wouldn't go as far as to say that kymco cdis are crap. It was just on that one model that has the honda based engine and just for a few model years (in the US) I believe. CDIs are usually an all or none type thing so that's why I was doubting the plug result. But I don't doubt your experience. Is there a problem with a resistor plug cap and a resistor plug versus having one or the other? I'm not sure. I think that can make a problem. Usually an R in the plug name will denote if it's a resistor plug. NGKs have always been good to me on average.

You could also easily check your reed valve. A cracked/broken reed could cause those symptoms as well as if it went into the crank case and chewed up the top end to reduce compression. running one day and not the next doesn't rule anything out. Sometimes things happen during trouble shooting but I'd agree that it's unlikely.

Kymco replacement parts are generally relatively cheap so even if you have to buy new it should be too bad.


 
MDVZ06
unregistered user
Sep-29-05, 07:03 PM (EDT)
 
11. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #10
 
   Experience? This's my 1st time working on one of these animals! Anyway, yes the plug(s) is an NGK/R #5539 or BR8HSA. They don't even come with the little screw on tip. It's not needed for this ZX-50 application. I also find it hard to believe that 2 brand new NGKs are both bad with really no use! How do I go about checking the reed valve? I haven't checked & I really need to. I bought a new carb and it was $89.99 which wasn't too bad, but I checked today on a price for a new petcock valve & they want $28.99 plus shipping! That's a bit steep, but if I need it I'll have to pay for it, not to mention shipping. Once again, THANKS!!


 
Brooke
unregistered user
Sep-29-05, 08:02 PM (EDT)
 
12. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #11
 
   Ha! I was just referring to your current experience. The school of repeated failure and frustration. Tuition is sometimes steep but the instructors are brutal.

I think that's very fair for a fuel valve. The usually run anywhere between 20 to 40 bucks. And cheap for a crucial part.

you take off the manifold, the part that attaches to the carb with 4 bolts at the base. The reed vavle will be right between the manifold and the engine case. It will have a plastic body and thin metal reeds (flaps). Try to keep the gasket intact when removing it, or order a new one with the fuel valve. You can get away with a little RTV blue liquid gasket goo to seal it up if your get in a pinch.

So this new carb, is it OEM or aftermarket Areche. If it's arreche, that could be the problem. I hate those carbs.


 
MDVZ06
unregistered user
Sep-29-05, 08:12 PM (EDT)
 
13. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #12
 
   Yes, the carb is a brand new OEM, not an aftermarket piece. OK, thanks on letting me know where the reed valve is at. I'll check this as well.


 
MDVZ06
unregistered user
Sep-29-05, 08:50 PM (EDT)
 
14. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #13
 
   You know, this scooter is still under the factory warranty & my girlfriend is the original owner. I have all of the paperwork. It was bought 6/30/04 & has less than 750 miles on it! I'm going to see if the Kymco dealer in Atlanta will send me the parts & cover them under warranty. Yep, fat chance of that happening; I'm sure they'll find a reason not to......


 
Brooke
Member since Jun-3-02
2807 posts
Sep-29-05, 09:19 PM (EDT)
 
15. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #14
 
   You never know. STR was pretty good at warranty stuff that I can remember. But doing the work yourself may have voided the warranty, but I'm not sure. As the dealer you got it from is no longer around, you may have to deal with STR motorsports directly. Explain the situation clearly and they may be helpful. http://strmotorsports.com/


 
Bryce Ludwig
Member since Dec-21-03
4441 posts
Sep-29-05, 09:50 PM (EDT)
 
16. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #15
 
   Doing the work yourself (or having it done by an independent mechanic) doesn't automatically void the warranty. Although, if they can show the work was not done properly, that can void the warranty in part or whole.

- Bryce Ludwig


 
MDVZ06
unregistered user
Sep-29-05, 10:07 PM (EDT)
 
17. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #16
 
   I'll try to get this taken care of thru this GA dealer (Moto Bravo). If not, I'll go from there. I just can't see spending the time & (GAS) money to transport this scooter 250+ miles to Atlanta just for them to find a reason to void the warranty. They already told me today that the warranty is for parts only, although the paperwork clearly states that the 2 year warranty is for parts AND labor. It just seems to me that since the local dealer (in business here since 1963 & now just went out of business; just my luck) is no longer in business, that providing me (actually, my girlfriend) the parts to repair the scooter would be fair & reasonable. But repairing this scooter by the process of elmination could quite possibly get expensive. Having dealt with car dealerships for many years, I know the lengths they can/will go to, to avoid repairing something under warranty. The bottom line is that if I replace the fuel valve (petcock) and the CDI box & it doesn't remedy the problem(s), further repairs will probably be beyond my scope of expertise, as I'm used to small block Chevys, not import motorscooters!! At that point, we may as well sell it on ebay for parts & be done with it.


 
MDVZ06
unregistered user
Sep-29-05, 10:08 PM (EDT)
 
18. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #17
 
   BTW, THANKS FOR THE TIME TAKEN TO RESPOND!!


 
MDVZ06
unregistered user
Oct-02-05, 07:46 PM (EDT)
 
19. "RE: Kymco ZX-50 idle problem, need assistance!"
In response to message #0
 
   The dealer in Atlanta told me that since I'd worked on the bike, the warranty was void. Then they told me that they were doing me a 'favor' by selling me the needed parts thru the mail, that 'they normally didn't do this sort of thing'. I wonder how these guys stay in business.


 

 

 


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