Did a search and found no info. Now that we’re up in the mid 80’s (Florida) it seems I’m losing fuel from my tank while sitting. Does anyone know how much fuel you lose through evaporation?

 

How much fuel are we talking here?

 

Up to a quart in 5 days?? Maybe. It only does it if I park it with around half of a tank. I haven’t measured it. Topped off tank doesn’t do it.

 

Evaporation? Zero.

 

That is highly unusual. What's the ambient temperature and is the bike stored outside or in a gargage?

 

How are you determining the amount of evaporation?
Does the bike have a carb or FI?

Ride on
Brewster

 

If you're using the stock tank/gas cap, it should be a sealed system. The cap has a pressure relief valve that will vent the pressure in the tank out of the overflow hose on the perimeter of the cap sealing surface. If you're using an aftermarket tank with a screw-on cap and open vent and the bike is sitting in the sun all week, you will evaporate some fuel, but I'd be surprised if it amounts to much volume.

 

Any puddles under the bike?

Could be leaking into the engine. Check your oil level. did the level go up? Smell any gas in the crankcase oil filler hole? Any weird startups?

 

How are you determining it is evaporation?

 

There's no way the bike would fire up if he were losing a quart into the engine in five days. That whole quart wouldn't all leak past the rings and mind you a quart is over 900cc of fluid, so it would be filling the cylinder multiple times over.