Vent lines for a 38MM Mikuni

I'm working on a '77' WR250 and I got my 38mm Mikuni carb mounted and was wondering about the vent lines. My carb only has two vent lines (one on each side). It does not have the bowl drain vent. Can I run both of these vent lines up under the tank or do they need to go down under the carb and out the back of the motor by the swingarm?? I would like to run them up high under the tank. I think they are just air vents or am I wrong?

Thanks, John

They're more than air vents. If you tip the bike over they allow the fuel in the carb bowl to drain on the ground and not flood the engine. I do wonder though why the bowl overflow wasn't included on these carbs. If the float valve sticks open then the engine will flood. Odd.

Link to an article to install an overflow to a float bowl that doesn't have one - (actual installation may be different, but the concept is valid):

https://www.souperdoo.com/stuff tha...-bowl-overflow-pipe-no-fear-of-fuel-hydrolock

Installing an overflow is a good idea, have considered doing it........some day. I've seen small copper hobby pipe on ebay for a few dollars.

I'll have to look at my bowl. I'm pretty sure that emboss is there but for sure there's no nipple on the bottom. Maybe I could fab one somehow?