2001 Suzuki quad runner 500 4 by 4 won’t start

[Bryzan3]

Looking for advice on what to try next I bought this quad and it’s has spark and fuel but won’t stay running only fires when I hold the starter button in even when spraying gas into the carb it still dies right away oil was milky white so I was thinking it maybe went under water 150 psi compression so I might be wrong but not a head gasket I am stuck Cause it should stay running with the straight gas through the carb so what should I try 

[Ajmboy]

Did you change the oil?

[Bryzan3]

Yes i did I just don’t understand why it won’t stay running if I am spraying gas directly into the carb When holding the starter in you could hear it start and  fire and rev up but when I let go of the starter button it just dies no matter how much gas i spray in 

[Old_ATV]

is it getting enough air?

[Bryzan3]

I think it is I think I am going to just tear the engine out and tear it apart I am thinking someone before me put something together wrong cause timing from the mark and valves seem right it should fire I have gas spark and great compression at least 150 psi  

[Mech]

That sounds like an electrical problem really rather than a mechanical problem.. I sure wouldn't be pulling it apart..

Have you pulled the sparkplug out after it's tried to start and looked to see whether it's wet or dry ?

I'm guessing that the starter circuit's somehow sending power into the bikes electrical system while you are holding the button in, then it's loosing electrical power when you let the start button off.. Do you have a wiring diagram ?

Do you have a timing light ? If you connect that up and watch whether it stops flashing as soon as you let your finger off the button, that would confirm my theory.

[Mech]

If it flashes for a few more times as the engine slows down, then I'm wrong...

[chimmike]

Something's up with the electrical system sending signal to the CDI, I think. At some point power signal to the CDI is stopping once you release the start button and it's a no-spark situation. Or maybe the CDI is bad?

[Mech]

Well since the cdi sparks when it wants to I doubt it's faulty.

In the smaller models there's a neutral relay that has wires going into it from the neutral and reverse lights and the kill switch and the starter button... If that thing has that relay I'd be checking it out and it's earth wire..  I see in the manual I have here for a 300 that there's also a diode in the neutral circuit.. that might be a suspect too.. You really need a workshop manual and then start tracing the power through one wire at a time going to the cdi unit. Check the neutral switch, neutral diode and neutral relay..  I reckon the problem will be in there somewhere..If your 500 is like the 300.