When engine gets hot cuts out HELP

[oldschoolsanta]

Hi ,
I have a big problem two days ago when i was riding my engine got hot and it stopped then it started again a couple miles later it stopped again i changed my spark plug and it started and i went home.The next day i checked the fuel,oil,carburetor and i bought a new spark plug.Now it starts when its cold works fine but when it gets hot it stops.Help me what can be the problem.

[MaryK]

It looks like your scooter is air cooled.  So, make sure that the venting is not plugged or restricted.
Is the current problem  new to the scooter?  How long have you had the scooter ?  How hot is the weather ?
When it overheats, is it due to being stopped or a lot of low speed riding ? 

These answers should help another Zx50 owner help you.

[oldschoolsanta]

Yes it is air cooled the problem started 3 day ago i have the scooter for a year i got 3500 miles on it.The weather is hot very hot it does not really over heat i ride it 300-400 yard and it cuts out i let it cool for half a minute and it starts right away and works perfect my cylinder is clean it doesn't have mud on it.

[MaryK]

Is the scooter under warranty ?

With older motorcycles, a faulty ignition coil can fail when it gets hot and work again when cooled off.
Also, the pulse generator coil might do the same. 
The reason is that broken wires pull apart when hot (expanded) and make contact when cold (contracted).

Vapor lock of the gasoline usually takes longer to cool off that a few minutes.
But, you could try opening the gas tank cap to see if there is a vacuum when the bike quits (doubtful).

Good luck and keep cool,

[zombie]

The stator/coil/cdi will all act the same. The other issue may be oil supply, or vacuum to the tank. Disconnect the fuel line, and suck on the vacuum line. The fuel should flow easily. If the oil level is fine, and the pump is working... I would just get the three Ign. parts, and be done with it.

[MaryK]

Since the stator is used to generate voltage for the rectifier & voltage regulators, I cannot see how it would be part of this problem.
Stator voltages can be measured and the battery should supply for any short term low output.

I agree that the CDI would be difficult to evaluate if it had a temperature related problem, so replacement is a good idea for it.
We had to replace the one on the Nighthawk due to failure after the voltage regulator failed and high voltage ate on the CDI.

Checking the DC voltage as a function of the engine RPM is always a good idea.... No more than 14.5 volts at higher RPM.

Of course all of these ideas are good to check out if you have the time and interest.
Replacement without evaluation is a good technique if you have the funds or lack the time and expertise.

scoot safely.

[oldschoolsanta]

Today i discovered that when i'am riding slowly not full throttle it doesn't stop.When i ride full throttle for half a minute it cuts out.I think that my oil isn't good or it overheats.Tomorrow i'am going to try a cooling mood.

[zombie]

"Since the stator is used to generate voltage for the rectifier & voltage regulators, I cannot see how it would be part of this problem.
Stator voltages can be measured and the battery should supply for any short term low output."

The stator has two outputs. One is for charging, and the second is for the cdi alone. They act/work independently.
You can remove the oil line from the intake, and crank the engine without starting it to verify oil flow from the pump.

[MaryK]

Thanks, Zombie. 
So is the stator winding used to power the CDI or does it function as the pulse generator for timing the spark ?

Thanks,

scoot safely,

[zombie]

That is the third portion of the stator... There is a small "Pulse coil" mounted for the cdi timing trigger. The main stator coils charge the cdi capacitor, and the Pulser coil triggers the firing point. The separate charging coils run the charging system alone. I have never seen a bad pulser coil but have replaced hundreds of stators that fail when hot. The main failure is due to insulation on the windings failing from vibration. As the coil heats it forces the windings together shorting the energy. When the wire cools it separates again.

[MaryK]

Again, thank you for the detailed information.
Our old Honda motorcycles do not use a multi-function stator, I & my DH learned a lot.

Next question is:  Is the tri-function stator used in most of the scooter engines from Asia
or is it just the smaller displacement engines ?

I see the pulser coil and the Stator coils on the electrical schematic for my GV 250, but the CDI is powered by the battery, not another coil,
so I am guessing that the smaller engines that can run without a battery use the tri-function stator.

Anyway, that you for your patience and excuse us for high-jacking this thread.

ride safely,

[zombie]

Ac, and DC CDI's run off different voltages but they both use either a magneto/rotor or an alternator. The only difference is the lack of a dedicated charge coil for the CDI. 

[zombie]

Forgot... They can both be triggered by either pulse coils, or hall effect sensors. Or even points if you prefer.

[thebatman]

When i 1st read this the 1st thing that popped in my head was i wonder about getting lean when WOT.........since i did NOT do it at low rpm

I read again and oldschool says 3-400YARDS and it'll cut out....... wouldnt that be the cdi?
I had an OEM CDI that was heated by the exhaust by mistake.(it fell down in front) IT would cut out the same way he described...

[oldschoolsanta]

It turned out that i ruined the cdi by derestricting it.So i need to find a new one.Which derestricted CDI is for the zx 50?