Buffalo tools 4,000 watt generator

The switch is probably generic.. go to a Lighting store and see if they have equivalent

If you can't get any info from the retailer as to repairers for you machine then check out other gen sets as most run generic carbys on the engines.

call buffalo tool parts dept.they have brand new tanks for $36.75 or if you need a petcock they cost $9.95 they also have the gas gauge for $9.60.call 1-800-568-6657

I'm not familiar with this particular generator however I would suggest trying to find a local repairer to get the armature rewound, which may well work out cheaper than buying a new part anyway.
Try searching Google Maps http://maps.google.co.uk/maps?hl=en&tab=wl In the search box type in 'armature rewind' and your location

There have been several factories in china that have made the motors used on buffalo generators, a couple of these are Lifan and J.D. as in Jiangdong.All of these motors are very similar to honda motors.The 6.5,13,and 15 h.p. motors are real brutes and hold up very well.

Idle speed jet or passage and/or high speed jet/passage is clogged. Remove the carb and inspect and clean thoroughly, then re-install. Set idle and high spped screws approx 1 turn and tune to run smooth from there.

First of all replace the on switch. The fuel tank is located on top so this unit is gravity fed. Check the inline filter for being plugged( if it has one). check the fuel line for kinks and blockages. Also check to make sure it has good fuel before starting.

Try Ebay for I did on mine

If it has been in storage with gas in it. it is gunked up. Need to remove carburetor and take to someone to clean carb.

Do a ohm test on armature slip rings with brushes removed.You should have continuity between rings but not between either ring and shaft.