I am new to the ATV world. I purchased a 100cc atv cheap because it wouldn't start. I replace the carb and adjusted the valves (.002 intake .003 exhaust). I am getting spark (tested with a plug tester). Any suggestions??? I have a new CDI on order. It smells like the gas is burning and I have no smell of raw gas when trying to start. I have great compression also. (pulled the plug and tried to start)Possible engine out if timing?? I believe i had the flywheel at TDC and the cam gear looked like it was at the right position when i adjusted the valves. PPLLLLLLEEEAASSEEE help

 

Did you get this solved?

I have a 150 BMX that was running find but difficult to start. I put a new carb on and it runs very smooth but still difficult to start. After several starts and stops, now there is no spark at all. I understand I need to check the wires coming from the CDI. From the pic in this thread, the green wires are ground, now I need to check the AC power. I turn my meter to AC put the red lead in the AC terminal and....put the black one where? Thanks.

 

I finally got mine started. It was a blown head gasket.

Check all your wire connections. Also make sure your ignition coil is securely attached to the frame. In my experience, i find just replacing the parts is easier than spending hours trying to figure what voltage is what. Parts are so cheap that it isn't worth the headache, plus it is peace of mind knowing that you have a new part.

Start with:
1. Plug
2. CDI
3. Ignition coil

all those parts shouldn't cost more then 40 or 50 bucks. Let me know how it goes.

 

I solved my problem, it was the kill switch grounding out.