I did a ride here in AZ at ranges of about 3000' to 6000' plus and it was well into 100 degree territory ...
I have done considerable research on this boiling thing and grizzly's and without having an extreme test fleet, I think the variables are this:
Gasoline is a volatile "solvent" ... It vaporizes very readily when warmed-up ... When the engine bay/lower gas tank area starts suffering heat soak, the gas holds a lot of heat being it is a 5 gallon tank ... I ride with several ranchers and a rincon and that day I was riding my new 500 foreman ... If you listened after they sat a while in the sun, they were "boiling" the fuel in the tank ... boiling meaning, excess fuel vapor in the free-space of the tank starts making a "boiling" noise and venting through the fuel system ... (cap) ... There are many formulations of gasoline in different parts of the country and in this many gasolines have different "vapor pressure" specs ... meaning some gas will volatize sooner than others and cause more vapors to the point to where fuel can "flash to vapor" when it hits a hot intake ...
Fuels with high ethanol content can and will vaporize faster sooner ... for example ... There are high elevation and low elevation formulas, and summer blends (high aromatics to lower hydrocarbon emissions) and winter blends ... My guess is if you have a fuel blend in your area that is inherently blended to volatize based on your area regulations, elevation, etc., etc., the grizzly being what it is, may still even under the right conditions, in certain areas have the issue even with the heat fighter kit update ...
Here are some tips you can do to help keep vapors DOWN in your tank ...
1. Try to keep it topped off on the hottest of days ...
2. If you plan on riding at high elevations, do not buy fuel at low elevations and drive to high as formulations can be different ... Solvent's properties change the higher you go ...
3. Don't park in the sun, park in the shade ...
4. If you have a volatility (boiling issue) try a different brand or add some Berryman's B12 which is mostly Xylene and it will increase the boiling resistance a bit along with bumping octane a bit ...
5. You can try running engine ice or water wetter, or run the bigger radiator from HL to try to slow some of the heat-soak, and run a continuous on fan switch bypass to keep the engine bay circulating at low or idle speeds ...
Finally, a little trick a few of us 450R guys do is we drain and completely rinse and flush our cooling systems of all green coolant and run a full flush of 50/50 dexcool and dump and refill ... It has improved surface tension over the green and we at least in our quads have proven it to run the oem cooling systems more efficiently ...
I have a very good friend that was part of developing this atv at Yamaha and worked for Yamaha for 16 years and we have discussed the dexcool thing and he as well says it is worth the effort to convert ...
It will not be one thing that you do to hedge against vaporizing fuel, but maybe a few things combined ... If you have an issue that is, otherwise don't sweat it ...
dez_griz