Marshin atv ive got a mid model 110cc marshin atv that wont seem to "fire'. What could the issue be?

SOURCE: no spark

check for the wiring...we used to bought some of those atv hummer style...and there is no continuity in the wiring because of bad terminal connexion to the inside brush of the cable...or you have a faulty stator....coil and cdi is not the main problem on those cheap engine....loncin,bears,zongshen....

SOURCE: 110cc atv

There are three things required for combustion to occur: Fuel, compression, and a spark (at the right time). One, or more, of these is/are missing.
If the bike has been in storage for more than about a year, then you can bet that the carburetor is plugged up. It will need to be completely disassembled and cleaned.
Also, check the compression. if it has a four stroke engine, it should be capable of developing at least 135 psi of compression (throttle wide open, choke fully open). If the compression is low (and it is a four stroke engine), check the valve tappet clearances. Insufficient tappet clearance will cause low compression.

SOURCE: i have a 110cc chinesse built atv. i got gas in

These engines are based on the awesome Honda design. Unfortunately, they do not have the same quality. If you verify there is fuel getting to the cylinder and there is also spark, you need to verify compression. One of the tendencies of these engines is the valves will actually tighten as they wear in. This can cause the valves to open prematurely which causes all kinds of starting issues. Check you compression and run a leak-down check to see what the compression portion of your engine looks like.

If you need to adjust your valves, do this with the engine cold and spark plug out.

• Remove the valve caps (I believe these are 17mm and they are located on top and bottom of the cylinder head.) There may be a little oil come out of the lower (exhaust) cap.
• Remove the left side cover. This is left side if you are riding the bike. This is the stator side and there should be no oil in this part of the engine. This will also allow you to turn the engine and align the piston with top dead center.
• Rotate the engine counter clockwise until the alignment marks, sometimes indicated by a "T" are aligned with the mark on the case. If both valves are closed, you should be at top dead center. If they are not, make one more rotation.
• Use a feeler guage to check clearance between top of valve and rocker arm.
  
• I believe you will need to use a 10mm wrench to loosen the adjuster lock on the rocker arm. Once loosened, the adjuster will screw up or down as needed.
• If needed, adjust the intake valve to:.05-.09mm and the exhaust valve to: .11-.15mm.
• Once adjusted reverse the process.

SOURCE: Roketa ATV-32 110cc Chinese ATV

Not that I have been able to find. The Chinese seem to be lacking in the information departments.