Loud POP, engine died & won't restart
 

Brand new to the world of ATVs. We recently purchased a 125cc Apollo Sportrax (made by Vittachi) quad bike. Hubby was riding it downhill yesterday when it made a loud POP and engine slowed to a stop. Won't restart. He says it sounded electrical.

Checked bike over, everything looks normal. Battery is fully charged, proper tight connections. Seems like she wants to start, battery juice is steady, starter and solenoid works fine, but she won't "catch" and fire. We're wondering if a fuse blew, or if it's worse? Has more than half a tank of gas, and oil dipstick read full before taking her out. He was driving about 15-20 minutes. This was her 3rd run since we bought her.

One thing about the bike is that after the last ride, the front screw holding on the gas tank had worked itself out, and as a result the top of the carburetor came off. O-ring, needle, and spring were all intact and clean so we screwed it back on. Started up perfectly after that.

No leaks, smoke, or other visible signs. What could the issue be?

Check for a spark by removing plug, re-fitting HT lead to it and laying it on head. Spin on starter and see if it sparks. Check compression, over 90psi is OK. Fit a new plug, even if it does spark.