If the dirt bike runs but sounds like its missing or not getting enough gas could the air filter being off cause this

There is no question, but sounds like it doesn't run with air box closed. It isn't getting enough air and that is usually caused by someone saturating the foam that covers the filter by too much oil. Remove filter thoroughly clean it, wash the foam with gas, let dry and then lightly coat foam with spray WD-40 instead of pouring motor oil on it.

This is sometimes caused by dirt in the gas tank. When the saw is off and being moved around the dirt settles to the bottom. The saw will start OK and rev up but after a while the dirt gets shaken up and sticks to the fuel filter in the tank. When enough dirt covers the filter the saw looses power or dies all together. Sometimes it will get enough gas to idle but not enough to run at high speed. With the tank half full, shake the saw to get all the dirt stired up and dump it out. Put a little gas in it and shake & dump it again. If you can fish the fuel line with the filter on it out, remove the filter and either replace it or blow it out. If this doesn't cure all your problems you may have leaks in the fuel line to the carb that are letting in more air than gas causing your power problems.

Did you check the filter? If the engine doesn't get air they it could cause it to die out like that. Also make sure that there isn't anything in the air line to the carb.

Did you check the gas line and make sure that you are getting enough fuel?

Did you clean the air filter ?. The bike will miss like hell if it is starved for oxygen.
The Air filter is normally a sealed box with a curved air intake and a rubber hose connected to the carburetor. Open the box and clean the sponge filter with petrol and squeeze it dry before reassembling. If you have access to 2T engine oil dip the sponge in it and squeeze dry before reassembling.Back firing does not indicate starving for fuel .

dirty air filter bike not getting enough air to run and there for too rich a mixture!

Your bike is running too lean. If you have not made any changes to the air intake or exhaust then your pilot jet may have something blocking it. (probably a piece of dirt, or just tarnish build up of fuel if the carbs aren't drained while in storage) By turning the choke on, you are reducing the ammount of air allowed into the "Fuel / Air" Mixture. This allows the bike to idle properly. Once the choke is off, the mixture has too much air and not enough fuel causing the backfire. If you haven't changed anything like the exhaust or air filter it sounds like a good carb cleaning is in order. Otherwise, you will need to change jet sizes to accomodate the difference in air flow.

Timing is right or it wouldn'trun at all. So now you need fuel and air in the proper amounts. If it's starving for either one it will cause the problem you describe. Start with the air cleaner and remove it. If it's really dirty this could be the problem. try to start the bike without it. If it still don't run then your probably not getting enough gas. possably dirt in filter (check flow to carb) or clog in mainjet. Also check for constant spark from your plug. If it's internittant you could have a coil going out.It's a process of elimination but always start on the cheap end. Air, fuel, spark then on to wiring nightmares. Best of luck.

hmmm, a few posibilities, might well be split cab diaphragms but overhaul should have spotted that. sounds like either too much gas or not enough, either flooding/gassing up or fuel starvation. could try running it without the aire filter too see what happens. it should run weak so if bike is better then you have too much gas, if bike worse then runnig weak to start with. I have seen this before with one particular cause.... petrol tap was leaking, gas runs past pistons when bike not running, soaks past and into crankcases. as breather recycles vapour back in to air box, when bike warm it's as rich sas hell. take of oil filler cap on engine and have a good sniff. you should smell only oil, if it's a strong smell of petrol, change oil and filter, dump petrol tap or see if new seals available.

Tune up sounds like the optimum solution. Depending on the area in which you live, the bike may need maintenance faster than scheduled in the owners manual.

Dust, Dirt, Pollen especially can cause a clogged air filter. Depending on which grade of gas you use, you may need to change plug(s) already.

I hope this information was some what helpful.