Problems with a motor cycle battery

[heathers]

Hi,
Apologies in advance if this is not an academic enough question for you,
I have a lawn mower that needs a motorcycle battery to start it.
The battery has to sit flat on its side.
The battery I have bought has a vent on the side and when I leave it on its side the battery acid leaks out.(Not good)
I am guessing that I need a sealed gel type battery if it needs to sit on side rather than one I fill up with electrolyte...or should I be able to use my refillable battery on its side?
Thanks

 

[mgb_phys]

You want a sealed/gel battery
Even if you fixed the vent, the plates inside a liquid battery are designed to have the liquid in the bottom.