[Hayashi]

Here is what I do.
> Completely drain the old.
> Add Preston cooling sytem flush fluid (from WalMart, Auto Zone, etc.) and bottled distilled water to the max.
> Ride the quad until engine gets hot (10+ minutes).
> Drain again when not too hot.
> Add distilled water only.
> Ride again until hot.
> Drain again when not too hot.
> Add 50/50 mix of coolant and distilled water.
> Be sure to use correct type coolant that is desinged for aluminum cooling system to avoid corrosion and plugging up of the cooling system. It is very important on your 400.
> Ride again until hot.
> Use hydrometer (that checks specific gravity of the coolant) and add either coolant or distilled water to fine tune. Coolant will raise and distilled water will lower the S.G.