Coolster 110 Won't Start

[papapill34]

New to the forum, thanks in advance for any help. Bought my daughter the atv for christmas, was running fine, then started having issues with staying on at idle, then went dead while she was driving it. Tried adjusting carb idle, checking for spark, everything looked fine. It just would turn and turn and turn but would not turn over. Then started messing with the ignition cable relay and it sparked and then the atv went completely dead, no lighs, nothing. So ended up changing the complete wiring harness, relay, solenoid, carb, gas lines, starter, stator, cdi, etc., battery, everything. Removed plastics to do so and disengaged the handlebars. Got new wiring hooked up last and it finally cranked up. Then the spark plug started smoking, so I turned it off. Turned on and did again. Decided to address that later and started hooking back up the front brake cables. Got those hooked back up, tried to crank again and starting turning and turning again. No clue at this point what to do. The front brake cable plugs were not plugged into the handlebars when I bought it. I don't know what to do with them. Not sure if that is part of the issue, or the handlebars maybe. Checked spark plug and it does have spark. When I try to crank, spark plug doesn't seem to be smoking anymore. Any advice would be great. Thanks!

Also, I will add that once everything started to smoke but it was running, it was hard to keep it running without pressing down on the throttle.

[MICRider]

I hate to say it, but with replacing so many parts at once without first nailing down what the original problem was, you've introduced numerous possible points of failure to what might have been a simple repair.
Wishing you the best of luck with it, I would try simple methodical trouble shooting of each system to try to nail down the problems.

[Jonny]

With all of this replaced, your motor is the direction I would point you.
Did you buy it new and if so, was it delivered to your home and did you drain the stock shipping oil and replace it. Not only is this not motor oil, but they more or less fill the entire engine for a safety measure.

Otherwise, it sounds like you may have sucked oil into the piston and plug combustion chamber which may be from having too much proper oil.
If that isn't the case, you may have some gaskets allowing oil to get in there.
Then worst-case scenario in this case, the piston is shot or worse.

If the oil doesn't prove to be the cause, I would disengage it from the transmission and see if the drive shaft will rotate. I know a lot about a lot, but I'm not sure you would be able to muscle it in high gear to see if it turns it freely. I'm on my first 4-wheeler and middle aged lol.
If it is used and the motor is the culprit, you can tear it down and rebuild it, or just replace it for $200. Once you get into the 250cc range, engines are $700 and up.

[clash 168cc]

Check compression. Check valve clearance. At this point going to a shop might be a good idea. Just changing out parts is not really analyzing the problem.