What 400 is that you are talking about 1970cs?
It was minus 40 degrees here a couple weeks ago. My carb'd Fuji engines in my older Polaris's started no issue. The new Polaris made fuel injected engines.....not a chance.
I have atv's, power washers, etc that have Subaru/Fuji/Robin engines and I have had zero issues so far.
Now I want to wait and see these before I buy the RTV 1100 diesel. And decide what I want more, another work machine or something more suited for trail riding to replace my Polaris's now that I hate my Polaris dealer.