No power on take off

[toothbrushhunter]

Have just purchased a GB400, when applying power it would die briefly then take off. I assumed this to be a fuel block in the main jet. Pulled the carb off, took it to bits, cleaned and blew it out. Put the bike back together and the problem is now worse. The bike idles but will not take power at all, if I move the throttle the bike dies completely till it is released.

The only thing that seemed strange when reassembling the carb was the thing at the bottom of the needle value that sits between the value and the carb body. It did not seem to fit snuggly in the body of the carb, it fell out when cleaning the carb. Or is the problem in the ignition spark Plug or coil?

please can anybody help.

[stanko]

maybe a hole in the diaphragm

[98tls]

Sounds like its flooding more than starving.Maybe a stuck float?

[riffer]

Nah. It's the emulsion tube for sure.

Its a vital part of the carb. The needle jet (or emulsion tube) has a tapered needle that goes up and down in it. If it doesn't sit right the petrol just flies through into the venturi and the carb goes immediately too rich. Of course its bogging down.

There should be an o-ring that sits over the emulsion tube when it goes into the carb housing. The whole assembly should be a pretty tight fit.

I suggest you pull the carbie apart again and make sure you have the emulsion tube placed securely into the carb body. And check for an o-ring there too.