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GY6 50 cc chinese scooter won't start. What could it be?

Hi.
I bought a 50 cc scooter that was sitting for some time. It's 2008 model and it had around 400 km when I got it. That's pretty low in my opinion. Well at first it was running fine. I mad around 100 km on the first day.

Well the second day it didn't start. Thankfully my friend helped me and he said that my carburetor is dirty. He celaned it and scooter started up. I made around 60km on the same day with no problem.

In the morning the next day my scooter wouldn't start. I tried to do the same as him. I cleaned carburetor and fuel filter but scooter still wouldn't start. It doesn't start electrically or kick start.

It's like 5th day and my scooter still won't start.
What happens when i turn it on:
 - sometimes it sounds just like a dc motor spinning but nothing happens (there is no cranking sound)
 - usually it makes cranking sounds but doesn't start
 - when I let it sit for a while (for 30min, 1h, day ...) it makes a sound like it almost started up but then dies

Thank you all for help!
I would like to apologize for my lack of english words in engines and bikes field (not a native english speaker and I'm not specialized in those fields).

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rickharris10 months ago

Tick these off as you eliminate them:

No fuel to carb.

No fuel through carb

No spark

Spark at wrong time

matijalazic (author)  rickharris10 months ago

1. Fuel goes to carb. Triple checked
2. I am not sure how to check that.
3. Checked it twice and even got a new sparkplug.
4. Not sure how to check that. Unadjusted valves?

For 2 you may just have to blow through all the jets. It depends on the type of carb.

matijalazic (author)  rickharris10 months ago

Thanks dude that worked :D I cleaned carb 3 times but I didn't know how clean those jets have to be. So 1 jet was indeed stuck. Fixed it with sewing needle.
Thanks again for all the help

For 4 check the timing if it is adjustable. Spark should be at or just after top dead centre of the piston.

I would add after everything else is eliminated:

Low compression

Leaking cylinder head gasket.

Too much air in the mixture - usually a leak.

matijalazic (author)  rickharris10 months ago

It could be one of this three because i once put my hand over air intake while trying to start it. It actually started that way. I got less air to engine.

Looks like you may have answered you own question. Weak mixture may be caused by a blocked jet as well.

matijalazic (author)  rickharris10 months ago

Yeah but i have cleaned really good. I let it soaked it 100% alcohol for 10 mins and cleaned it with petrol. I also blowed thru them. I have 2 questions.
1. Is there a way I could clean them better?
2. What should be position of air-fuel mixture screw?
Thanks for everything so far.

seandogue10 months ago

Is there a "choke" on this motor? If so, a cold start often requires the choke to be engaged to restrict air flow during warm up. If it uses an automatic choke, it may be gummed up or otherwise isn't operating as designed..

matijalazic (author)  seandogue10 months ago

Thanks for help :)
I gess i was really sloppy when cleaning carb. 1 of the jets wasnt clear enough. Cleaned it with sewing needle and my scooter works again :D so happy

Your welcome!