I've had my Yam 2400 for about 5 years now and have been happy with it. It has NOT, however, been able to consistently start either of the two 13.5 ACs I've had (08 PU and current 12 Roo - Coleman). I have a new capacitor that I plan to install today, and hopefully it will remedy the issue.
When researching to purchase the 2400, most of the information I found indicated that it should run a 13.5 AC. It's been disappointing that I have the added weight without the benefit. If the capacitor mod allows me to run the AC when needed, it will be worth the added weight. Although I'm not yet too old to make the added weight prohibitive (45), the 80ish pounds is to be respected.
I've used the fuel shutoff as the normal procedure when stopping the generator, and have had no gumming issues. As much as I try to run it at least once a month, It sits longer than that most of the time. Seafoam once in a while, and starts without issue.
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I just added the SPP6 to the AC unit and the Yamaha started it up. The true test will be once the weather warms enough to need the AC. Hopefully this has solved the problem.