My bike has a carb...no fuel pump for me other than gravity. I drew a vacuum on my petcock and drained the tank until empty but there was a fair amount left when I removed the hose.
I installed the same horn. Except I split it in half and put the compressor under the seat and the horn under the cowbell to keep the stock look. They are connected with a black hose. I installed the relay that came with the horn. You have to trim down the plastic horn piece for it to fit under the cowbell but it's just plastic so it trims easily with tin snips.
Just got this horn in the mail. Looks awesome. There are only 2 wires connected to it. Did you use a relay to install? If so how did you do it? I'm clueless with wires...