How long can I let my race fuel stay in the tank before it causes damage?
Really depends upon the fuel.
VP seems to have the biggest problem in some of the MR series fuels. I think there's some napthalene in there that causes problems in the tank and in the fuel lines, etc.
Pump gas is really only built to last 14 to 28 days before it deteriorates. Doesn't generate any huge harm. Most other racing fuels are still built with the recognition that racing fuel is not used immediately, so it doesn't degenerate so fast. It's all related to its exposure to air and how much surface area is available to that air. If it's an oxygenated fuel, then the oxygenate will evaporate off too. That happens quicker than the fuel turning into something else.
Maybe that gives you a start for more questions.
If it is the oxygenated go fast juice like Dave alluded to, get it out as soon as you're done riding. Some of the U4 varieties will start working on valve guides, fuel pumps, and rubber components in the fuel system immediately. Better safe than sorry.
i use vp ms 103 unleded and leave it in the bike and never had a problem yet.When i used u4 then i would put pump gas after the race is over.
Some of the factory teams last year had special fuel pumps to pump out the vp fuel when the bikes came into the pits. Pictures of this were in RoadRacing World last year.