Easy
Something you might try and that is drill out the barbed fitting for a larger inside dia. both ends but you will need to take them off the bike. You do not want the shaving in the engine. Your line looks close to the same size as mine..I drilled out the barbed fitting. This might give you some hidden extra, or it will screw it up, but you can get new fitting as they aren't expensive. I drilled out the inside of the barbed fitting to .189 or a #12 drill you can try and go larger if you want to I settled on that dia.
This is the bottle I rermoved off my 70cc its at 68cc for bottle and close to 69.8 cc with fittings
This is a 69cc bottle on my so called 80cc
