Strange vibration at high revs.

[MEXICO SCHWINN]

Could some one tell me the reason of a Strange vibration when the enging is high rev. at full speed. It also chokes until you lower throtle, like if no gas was going trough at high revs.

I live in Mexico City 6000 ft + above sea level, My needle set up is 2nd from top to bottom, and the rear sproket is a 50 teeth one.

Any sugestions???

[spunout]

Could some one tell me the reason of a Strange vibration when the enging is high rev. at full speed. It also chokes until you lower throtle, like if no gas was going trough at high revs.

I live in Mexico City 6000 ft + above sea level, My needle set up is 2nd from top to bottom, and the rear sproket is a 50 teeth one.

Any sugestions???

first suggestion is perhaps re-word the symptoms. example: first you said "engine is high rev. at full speed", if thats the case, then how could it seem "like no gas was going through at high revs"? without gas going through, you wont have any revs
the vibration could be many things. is it true vibration you're feeling, or a loud 'whistle' sound you're hearing? im certain you checked and re-checked all nuts and bolts? hows the lateral true on rear sprocket? is this a new build, or just a new problem?
throw out more info, and someone here should pick this up 8)

Oh, and welcome to MBc!!! 8) 8)

[BikeHacker]

Check your intake for leaks by setting a high idle and slowly engaging your choke. if the engine runs on then you have an intake leak. reseal your intake manifold with RTV if it was never sealed it will leak .... check your plug color. If it is white you have an intake leak or it is running lean. For high alt get a carb with an adjustable jet to dial in a black or brown plug.

Hope this helps

You got a link for one of those carbs?