Here's something else you can try. Remove the sparkplug and pour a Pepsi bottle cap or two of gas down into the cylinder. One capful is probably enough, but you will likely spill some trying to pour it into the sparkplug hole, so it may take two. Quickly, put the sparkplug back in and put the sparkplug wire back on and see if it will start for a second or two. If it does, and your fuel pump is pumping good, you will need to remove the carb and give it a good cleaning. You can also put some gas in a spray bottle and spray it into the back of the carb and get the same results.
Also, it's not too hard to check and adjust the valve clearance.
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.