Yamaha mto3 sitting for 3 monts outside, battery

You could load test the battery ,to see if its good ,if it is good or new,it may be your stator,or charging system.You could check the voltage of the battery while its running to see if its charging. I found ,they dont like not being started,or sitting for awhile. Ive installed a battery tender ,that keeps my battery fully charged even if you let the bike sit for extended periods of time. Its a very low amp charging system ,then turns itself on and off,to keep your battery fully charged. Sometimes there called Float chargers too.

Dead fuel in the float bowls, turn fuel tap off get a piece of thin hose connect to the drain fitting on the float bowl release drain screw on the bottom of the carbs drain each carb, top gas up with good fuel turn tap on and your off.

Hi, Do you have an alarm & Immobiliser fitted on your bike as these drain the battery on your bike very quickly? If so i would recommend removing your battery and fully charging it with a decent amp-age charger. If you have your garage attached to your house then i would definitely recommend purchasing a trickle charger and when not using your bike keep this plugged into the mains and you should not have this problem again. all motorbike shops sell these chargers If after this the battery goes flat again i would suggest purchasing a new battery. This is a common fault as most motorbikes sit in the garage through the winter months and if not kept on charge will deteriorate. Hope this helps.

if the starter wont turn the engine over try putting the bike on its center stand plonking it in top gear and turning the rear wheel to see if the engine is sezed up,, it may just be very tight,,,or the starter may have set solid from lack of use, also the battery is by now dead,,,18 months stood doing nothing and not chareds very often wont do it any good at all, try using a car battery to jump start the bike