worked for a while, backfired, now wont start...

I built my first bike about 2 years ago. It's a JET SILVER 80CC motor on a huffy cranbrook. I got it running, and used it around town quite a bit. I was showing it to a friend, and he grabbed the throttle, goosed it, and it made a HUGE backfire! Immediately following that I rode down a hill, the bike died, and I have never been able to get it running since. It has been in storage for most of the time since, because I have moved around a bit, but I have looked at it a bit from time to time, with no luck diagnosing, or fixing it. I have taken the engine apart, checked for anything out of the ordinary, checked the spark plug for signs of it being burnt, made sure the fuel is still flowing, made sure everything is tight and sealed as best as I can. I have seen a bunch of people suggest using a volt/ohm meter to check for spark or to check the magnito, but I don't exactly know how to do that... Has anyone ever experienced this or something similar, have any advice, or does anyone have any ideas of what to check?

Thanks so much in advance for the advice.
-Chris

Greg58 said:

Have you checked for spark? remove the plug then plug it in the plug boot and lay the plug on the head, then push the bike with the clutch released so the engine is turning over. You should see the arch from the plug. The link below will help also.
http://motorbicycling.com/showthread.php?t=35090

Click to expand...

Thanks for the detailed info! I have not tried that yet, but I definately will give it a try tomorrow. If you have any other ideas, let me know!
-Chris

So last night I spent about 5 hours working on it, and still no luck. I started by pulling the spark plug outof the engine, keeping the plug in the boot, and looking for the arc while pushing the bike without the cluch engaged. Success. I then took a volt/ohm meter and tested the leads from the engine, and read ~330 ohms. I also tested it while moving, to check the starting capacity, and it read between ~38 and ~55 A/C volts. I don't still have any specs on the engine, so I don't know for certain that these are good readings, but I have a feeling (based on a few different videos I watched) that these are ok. I flushed out the gas tank and filter, just to make sure that there was nothing clogging the flow or contaminating anything. I took apart the exhaust, cleaned it, and nothing seemed out of the ordinary. I took apart and cleaned the carb and air filter.

I then tried to check for spark with the plug out of the engine and in the boot again, because by this time it was dark out, so I figured I could see it a bit clearer. I noticed that the spark was very intermittent. It would arc concecutivey for a bit, and then miss here and there. Spark again for a bit, and then blank for a bit.

I took the wire from the CDI to the boot out, clipped the ends off, and rescrewed it in. I tested it again for arc, and I couldn't tell if it was much better. I did notice that the connections from the engine to the CDI (black and blue wires) were questionable, so I will have to either put new connectors on or solder the connections together, which I haven't done yet.
I don't know if the arc is inconsistant because there is no seal and compression around the plug, or because something is faulty.

I am running out of ideas, as well as I feel like I am looking for a solution to a problem that I don't know...

Anyone got any ideas...?

Thanks,
-Chris