Is the 1999 Yamaha blaster oil tank needed?

no the oil tank isn't needed. but you will need to premix your fuel and oil. have a gas can you can have your premix in and mix about 4 ounces of 2 stroke oil for each gallon of gas. if the exhaust smoke is very smokey, use an ounce less oil per gallon. if theres very little exhaust smoke. add an ounce per gallon. when the exhaust smoke looks like it did when the oil tank was used. then use that mixture ratio. but, don't run very long with very little exhaust smoke, or the piston rod bearings will burn up. then its very expensive to have new ones installed. it will damage the bearings, crank pin, and piston rod. its always better to run a little too much oil in the gas than too little. if you use too much oil. it only fouls the spark plug. easy fix. clean the plug and reinstall.

The blaster runs a 32:1 ratio on oil/fuel. Also you will need to block off oil mixer on right side of crankcase and run a jumper wire on the oil safety switch