Trying to get this 800-mile cheap Chinese scooter running reliably and it seems be down to a fuel/air mixture issue, even with a new carb and fuel and air filters. I need a little advice on how to get this thing starting and running without a lot of manual intervention. I’ve never really worked with carbs, so I’m not sure what I’m getting wrong.

1) There’s a hose connection on the manifold between the engine and carb. There’s a plug on that connection, but if the plug is pulled (more air into the engine) the engine starts, but doesn’t run well until that plug is replaced. Starting the engine without that plug in place is almost impossible.

2) The only two adjustments that I can see are the low speed mixture adjustment and the throttle position. I’ve followed most of the advice and turned the low speed mixture screw all the way in and then backed it out 1.5 to 2 turns. Backing it out further doesn’t have a major effect when the engine is running, but it is noticeable; when backed out further the engine seems a little less responsive to throttle inputs.

3) The engine doesn’t seem to run well with the stock airbox in place, so a washable cone air filter was installed and it seems to run stronger. It runs about the same with either the cone filter or no filter installed making me think that there is some sort of obstruction in the airbox (currently bypassed)

I’d like to see this engine start reliably without having to pull any hoses, and I think it should have a steady idle without enough revs to turn the rear wheel when on the center stand. What am I missing, and what can be done to turn this temperamental PoS into a reliable commuter vehicle?