Scooter won’t start
 

Hi,
New poster here. I just acquired a 50cc gy6 scooter. It ran ok, I shut it off and it sat for a few weeks in the garage. When I went to start it, starter spins engine over just fine but it won’t fire. I did replace the spark plug, as it seemed spark was weak, I even put in a new CDI box. Today I tested gas flow, none flows from gas line at the carb when I crank the starter. I pulled off the vacuum line from the intake manifold, which goes to the vacuum petcock. When I suck on this line, gas flows from the fuel line going to the carb. So, it seems the vacuum petcock has failed. Does this seem right?
Anyone ever have a similar problem? How did you fix it? Put in a manual petcock with a remote shutoff valve in the fuel line? Any suggestions?

I would personally go the basic manual petcock route. That sounds like a great solution to me. The less complicated you can make the thing the easier it will be to diagnose future issues.

I had the same problem so I put a new vacuum petcock in and the problem was resolved. My petcock was under the tank so it was a bit of a pain in the ass to change but it did fix the problem.

Pappy

Did you check and see if the vacuum fitting on the carb is clogged. If you suck on the line and it flows the petcock should be working. I had a similar problem once and it was the spark plug. Replaced it and the scooter ran.

Vacuum petcock is the first thing that goes in the trash and gets replaced with a manual one or an on/off inline valve. Have had way too many issues with them in the past.

From what you say, the vacuum petcock is working ok. Try filling the carb bowl by sucking on the vacuum line and then trying to start it.The most common problem with engines that sit awhile is gummed up carb jets. Your next step should probably be a good carb cleaning.