Originally Posted by Airhead Wrangler
Now that I've thought about it a little, spraying into the airbox (after the filter) would still probably get the air filter wet. It might be better to spray directly into the intake tubes, but would it be ok for mist to go through the carbs? You could even use those two holes that are already in the side of the rubber bellmouths.
Mounting the nozzles in the air filter box get water into the carbs also, so after the carbs is the only way. Rather than water, use cheap windshield washer fluid (alcohol/water) I have methanol injection set up on my turbocharged Subaru, the system that I use has a two stage pump that only works under heavy load (med/high boost pressures). the amount of meth injected is controlled by nozzle jets. You need to be careful not to over do it, as I have seen rings broken, and oil fouled. In extreme cases piston and con rod damage as water does not compress. My worry with an N/A carburetor engine would be pulling fluid into the intake under high vacuum, so a check valve would be needed along with a pump strong enough to overcome the check valve. I don't know about a motorcycle, but my scoobie goes thru 2 gallons in about 100 miles of spirited mountain driving.