scooter dying possibly due to flooding

[superdan54]

I've got a 2005 Kymco ZX-50. As the subject says, the problem i'm having is that my scooter will just cut out at various times. Usually this happens just after filling up for whatever reason. I will start fine, but after driving a mile or so, the scooter will just cut out, and giving it any throttle causes it to die. However, if I let it idle a while, then I can proceed as before, however it may happen again in another mile.

It also has a hard time starting occasionally, but it's hard to really the pattern ironed out. The starting problem seems to happen most if I drive several miles, and then let it sit for a while. When this happens I usually have to kick start it to get it to run. Also, after driving this distance, I'll hear a pop of compressed air come out the exhaust when I turn the key off the ignition, something I don't hear in my other scooter under the same conditions.

With all that said, I think the problem is that it's getting too much fuel, but I'm not sure why. I have replaced the carburetor and auto-bystarter, the petcock and the battery. I've also checked the fuel filter.

Previously it was suggested to check the idle adjustment on the carb, but it doesn't seem to run high like it would if it was getting too much gas (I had this problem on my other scooter).

So I guess I'm just not sure what else to check!

thanks in advance for your help!

[superdan54]

I did have a thought, could the problem be that it's getting too much air instead of too much fuel?

[als01seville]

Well if its popping its running Lean, check for air leaks around the intake and vacuum hoses. Also after you fill up and it starts to die open or just crank the gas cap it sounds like your tank is not venting and will stop the fuel from flowing fast enough to fill your carb bowl.

If your at wot open throttle and it starts to loss power and you back off the throttle a little and it picks up YOU ARE LEAN.

Here's a simple and quick way to test if you are running Lean or Rich at Just about any Throttle position,WOT, Low Speed, Mid Range etc..

When you notice a Stumble, Back off the throttle a little 1/8-1/4:
1. If it surges ahead your Lean
2. If it stumbles and recovers your Rich

Now depending on where in the Throttle position this happens Different settings have to be done:
1. If it stumbles as your starting off - Adjust your Air/Fuel Mixture
2. If it stumbles in the mid range - Adjust your Needle
3. If it stumbles at WOT - It could be your Air/Fuel Mixture or you may have to Re-Jet.
Alleyoop

[superdan54]

That is VERY helpful info! Thanks!

One quick question before I start my testing, I think what you are saying about the tank not venting is spot on. One thing I have done in the past is to loosen the gas cap. It has a pretty tight seal otherwise, and I've found that this alleviates some of the problem, especially the problem of it dying soon after starting.

Since this seems to be part of the problem, what can I do to fix that? My father in law suggested drilling a small hole in the cap or top of the tank. Does that sound right or is there something else I could/should do?

[superdan54]

ok I think I fixed the main problem. Apparently when I replaced the petcock, I tightened it to where a kink in the fuel hose developed over time. Now I'm able to ride w/ pride!

However I'm still having some starting issues. I'd say a good 40% of the time it starts up fine, but sometimes it just doesn't for whatever reason. One thing that does seem to happen consistently is that after attempting to start 3 or 4 times, I'll hear a shot of compressed air coming out the exhaust. After this the scooter starts.

You mentioned before that popping was due to a lean mixture. I pulled the spark and it's brown, and I have a slightly rich setting on my air/fuel screw. I'm wondering now if the starting problem is electrical in nature. The reason I'm asking is that all of my problems seem to arise from a vacuum that is created when I turn the key on to engage the electrical components (starter, CDI). The same vacuum is also released when I disengage the electricity, (i.e. killing the engine doesn't cause the pop of compressed air, but turning the key off does).

Could the CDI be bad or something like that?

[arigold]

Did you change all your vacuum hoses? Just for good measure?? It's cheap and easy.

[tomcas]

May 4, 2010 15:58:58 GMT -5 superdan54 said:

ok I think I fixed the main problem. Apparently when I replaced the petcock, I tightened it to where a kink in the fuel hose developed over time. Now I'm able to ride w/ pride!

However I'm still having some starting issues. I'd say a good 40% of the time it starts up fine, but sometimes it just doesn't for whatever reason. One thing that does seem to happen consistently is that after attempting to start 3 or 4 times, I'll hear a shot of compressed air coming out the exhaust. After this the scooter starts.

You mentioned before that popping was due to a lean mixture. I pulled the spark and it's brown, and I have a slightly rich setting on my air/fuel screw. I'm wondering now if the starting problem is electrical in nature. The reason I'm asking is that all of my problems seem to arise from a vacuum that is created when I turn the key on to engage the electrical components (starter, CDI). The same vacuum is also released when I disengage the electricity, (i.e. killing the engine doesn't cause the pop of compressed air, but turning the key off does).

Could the CDI be bad or something like that?

I'm not sure what you mean when you talk about a vacuum thats created when you turn the key on. The only vacuum created is when the engine is rotating. It's also hard to imagine the CDI working sometimes but not others unless a marginal component was effected by something like moisture or temperature. Could that shot of compressed air be an ignition of accumulated gases within the exhaust?

[als01seville]

When you turn the Key On nothing is rotating so there shouldn't be any noise whatso ever Unless you have an Electric Pump. That would be the only thing that could make any kind of noise when you turn the Key on. There is nothing that will move just by turning the Key on.

Pulling the Spark Plug will not always tell the Truth. Don't forget to check the Plug Probably you have to run it at WOT and CUT THE ENGINE and pull off the Road and take the Spark Plug out. If you run it WOT and then go down sidestreets to your house and slow down and stuff that changes the Color of your Spark Plug.

I STILL say your running LEAN due to the Popping IF its still Popping. If it POPS only when you slow down to say 10 miles an hour and let the Throttle go to stop THEN its more likley that you have a Leak by the Header Pipe and Head.

Also when was the last time you adjusted your Valves, how many miles on the Scoot?
Alleyoop