Taotao dying at wide open.

[badfish888]

So my buddy has a taotao with the 139qmb.
He FaceTimed me to try and help trouble shoot. (He is in VA) I’m now in CT.
Any way. Bike starts, idles and will run great u less you go wide open. After about 30 seconds it will gradually loose speed/rpm and if you don’t back off the throttle it dies. Changed the carb, fuel lines, filter, plug, and tried running with gas cap off. ZERO difference.
Rollers are new and variator is clean.

[scooter7878]

I would check for vacuum leaks especially the intake and vacuum hose to the petcock and also the petcock it could not be supplying enough fuel to fill the bowl fast enough at wot or a leak in the vacuum hose or intake can cause the petcock to not open enough to fill the bowl. Or a issue with the float hight. What ur describing is def a fuel supply issue. Maby for shits check valve adjustment too

[GrumpyUnk]

If the diaphragm in the vacuum petcock had a slight leak, any decrease in vacuum from the intake manifold, such as running at WOT, could allow the petcock to slowly close and shut off the fuel supply. One other possibility is the seal on the carb->intake elbow, or the intake elbow->intake port on the cylinder head. There are one or two vacuum ports on the elbow that should be sealed or connected to vacuum devices. If any of those vacuum lines or the device they operate have leaks, again, vacuum would likely drop allowing the petcock to slowly close... Dunt dunt DAH.
tom