yamaha ef1000 generator leaking fuel

[carldebjez]

Hi, this great little genny runs well but has just started leaking fuel out of the overflow hose in to the case. When turned off it will empty the tank. It seems like a pressure build up as it 'wheezes' when the run switch is moved from off to on. The fuel cap has a screw on the underneath with a small metal cross piece held in place by the screw. Any ideas where the tank vent is, and how to unblock it if that is my problem?
This is the model of generator, shown in this video


Cheers, Carl

 

[Conquistador3]

Those old Yamaha generators are very prone to this issue.

It usually goes somewhat like this.
Fuel is left sitting in the tank for too long
Fuel slowly dissolves the pettycock gaskets
Fuel flows freely into the carburetor bowl
Extra fuel gets through the needle and out of the overflow hose

The good news is if you are familiar with fuel system rebuilds this is a pretty straightforward repair. Taking the carburetor apart to properly clean it (unleaded fuel left too long in it = varnish; if there's any ethanol in the fuel make it even more varnish) is a good idea at this time.
The bad news is that while parts for these generators are still easily available from any Yamaha dealership they are so expensive they make Honda spares look cheap by comparison.

Here's a extra little advice for you: when you are taking apart the thing, stop often and take plenty of pictures. They cost nothing, you can delete them at a later date and will save you a ton of time during reassembly because literature for these generators seem inexistent and they have some, shall we say, peculiarities that may make a saint frown when reassembling.