Recently I purchased a [Yamaha EF2000 generator](http://www.amazon.com/Yamaha-EF2000iS-4-Stroke-Generator-Compliant/dp/B002RWK9N2/ref=sr_1_1?ie=UTF8&tag=prodctid-20&qid=1384023151&sr=8-1&keywords=ef2000is) and decided to do a Natural Gas conversion.
Motor Snorkel by US Carb
I got a kit from US Carb for around $180 which included a Garetson KN style regulator (such as those made by [Century](http://www.amazon.com/Century-Garretson-Pressure-Regulator-Converter/dp/B00EP1N1X8/ref=sr_1_sc_1?ie=UTF8&tag=prodctid-20&qid=1384023277&sr=8-1-spell&keywords=garetson+kn) or [Impco](http://www.amazon.com/Impco-Garretson-Regulator-Vaporizer-Converter/dp/B00EP1MYPY/ref=sr_1_sc_2?ie=UTF8&tag=prodctid-20&qid=1384023277&sr=8-2-spell&keywords=garetson+kn) and a “motor snorkel” kit which is a sort of shim that goes between the air filter and the carburetor.
I also got two [“Mr Heater” quick disconnect hoses](http://www.amazon.com/Mr-Heater-Assembly-Disconnect-F273720/dp/B000K6JF82/ref=sr_1_3?ie=UTF8&tag=prodctid-20&qid=1384024258&sr=8-3&keywords=natural+gas+quick+connect) – one of which you see pictured above in front of the Yamaha EF200is generator, which allow me to switch between this and my [webber natural gas grill](http://www.amazon.com/Weber-Genesis-6631001-637-Square-Inch-Natural-Gas/dp/B0045UBB2M/ref=sr_1_4?ie=UTF8&tag=prodctid-20&qid=1384024360&sr=8-4&keywords=webber+natural+gas+grills) pretty easily. US carb has some info on this.
You can also use it with propane – nothing changes on the generator and the KN style regulator – but you will need to use a propane regulator to get the line pressure feeding the KN style regulator down.
It runs well and was pretty easy to install. Total cost was around $1200 with the generator being a little under $1000 [on amazon](http://www.amazon.com/Yamaha-EF2000iS-4-Stroke-Generator-Compliant/dp/B002RWK9N2/ref=sr_1_1?ie=UTF8&tag=prodctid-20&qid=1384023151&sr=8-1&keywords=ef2000is).
