scooter shuts off at high speed

[94fordman]

was riding to work today and was at high speed and scoot shuts off and slows down then runs fine have a 50cc jonway 20 mm carb with 6hix plug insted of 7hix woundering if thats the prob

[beachbum]

Does it bog and then when you let off the throttle does it pick up again?

Does it do it right away when you hit high speeds or does it do it after you've been at high speeds for a while?

[94fordman]

every so often it does this just as ur riding at high speed then it bogs slows then u can speed up again

[qwertydude]

Likely the larger carb is reducing vacuum to the petcock and shutting fuel flow off. To help maintain vacuum to the petcock you can do a few things, completely remove the smog system and block off the exhaust PAIR vent. This also greatly simplifies hose routing. Then run the vacuum line direct from the intake manifold to the petcock, when you remove the smog system this makes it a direct run with no T's which can reduce vacuum to the petcock.

You might need to switch to a manual petcock.

[beachbum]

I was having a fuel flow problem on my 150cc at long durations of high speeds, but I haven't heard of this happening to a 50cc. It does seem like that is what your dealing with. You can try what Qwertydude suggested or get a high flow fuel pump.

Just curious, did you perhaps overfill your tank just before this happened? Sometimes if the fuel tank vent gets filled with gas you'll run into the same problem.

[94fordman]

tank wasent completly full. theres a line going to petcock frome intake then to carb

[qwertydude]

On a proper running system the tank not being full shouldn't have an effect. You should be able to run all the way to last drop. I still think it's reduced vacuum from the larger carb. When people install a larger carb they almost always also install a performance intake. Both those can reduce intake vacuum to the point where the petcock isn't working. You can also try running a manual petcock.

[savy09]

Yeah, the over fill hose may have a bit of gas(vapor) locked in it, disconnect it from the tank end and petcock, blow air in to clear it and re attach... also may be building up vapor in tank running full, then crack open the filler cap to free vapor, ck you may have to drill a small hole in the cap. Also ck your intake manifold, T hoses, and to the petcock for blockage blow them out.

[Lefty]

First thing I woud do is change out the Plug get a 7 the 6 is to HOT of a plug and try that.
Lefty

[94fordman]

k cool will try