2002 Trailblazer won't start
 

I'm new to the ATV world and bought a used 2002 Trailblazer last month. It started fine and ran great until 2 days ago. After parking overnight, it wouldn't even hit once. It turns over fine, I have a wet plug, a spark (maybe a little weak) and 80psi of compression. I have replaced the coil and today, I cleaned the carb and installed a new needle and seat and carb adapter. Still no hits. Is it the CDI or is my compression too low to start?

80psi compression!!!!! looks like you need a top end rebuild. You will be able to get it started with some work when its cold due to the low compression. You should have minimum 100psi for easy starting and recommended 150 to 120psi compression for normal use.

A top end build is on my to-do list, but I wonder why it began all of a sudden. When it was a little warmer it started and ran fine. Is a spark a spark or are there weaker sparks than others? I'd like to rule out the electrical or fuel systems.

you could use something to warm up the block,a lil torpedo heater or space heater. then it'll start

personally i think once you get the compression up to over 100psi you will not have any starting issues. I`d be looking at the top end rebuild first before doing anything else. I`d almost bet everything on your quad is fine so don`t worry about the spark or anything else until you get enough compression. here in Canada a cylinder bore and piston kit will cost about $200. providing you do the labor on the re and re.

id try a new plug first, did u have the throttle wide open when u did compression ive seen readings jump 15 to 20 psi with throttle closed and throttle wide open