New 66CC will not run.

this can be a pain to do. mark the mag rotor so you put it back on the same way you take it off
Take the mag coil and then the mag rotor off see if the key is sheared. If it firing the spark plug,and has fuel it should at least pop. Other wise it has a key missing or sheared my best guess.
When its out of time it won't run found this on a few engines.
On thing make sure when looking at the mag rotor the slot is leaning towards the right a little bit
they are slotted off true to the hole so the key way on the rotor looks strange. Proper way to put them on is with the rotor key will have that ever so slight lean to the right or towards the front sprocket.
Ho this will help.

Well I'm not sure about troubleshooting with engine parts, BUT what I do since my engine had EXACTLY the same problems as yours did is to spray a little bit of ether into your air filter, THEN try running it. My engine is naturally cold if I don't run it for a month so I have to spray that in there to give it a little extra push. Just unscrew your air filter off your carb and spray a tiny bit of it into your carb where your throttle pin is.
This works for me everytime.

A_DangerrX said:

Sunday morning status report:

One more issue that has come to my attention: Unburned fuel has dripped out of the joint between the exhaust pipe and the motor. Could a leak there be affecting ignition?

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When i had a bad/worn out exhaust gasket and had a leak,it would be much harder to start.
I put in a new exhaust gasket and tighten the nuts and wammo its starts right up and starts up the first time every time now.

Can you see the key in the rotor shaft? Is the rotor key way and key way on the shaft alined?
It might be too hard to see both. But if the key is sheared or not even there it won't run.
You can't turn the rotor by hand or some light force with the gears locked (shop rag wedged in between the teeth of both gears) on the other side(clutch side) can you. If you can turn the rotor with the gears locked the key is toast. Then you will need to take the rotor off to replace the key.
The rotor is a booger sometimes to take it off. gently wiggle it to work it off.
I made a small hooked tooth pry bar for those hard to get off rotors made it out of a 10" length of 1/4" key stock heated up one end and beat a small hook on its end to get under the rotor to pry up on the rotor
2 of the pry bars will work better than one. you can work the rotor from both sides then.
If you plan on leaving the rotor off wrap the rotor with a band of mild steel. Metal from a tin can will work wrap it tightly so the rotor contacts the steel on the curved parts a stainless steel hose clamp is not good has to be mild steel from what I've been told. I'm finding that the rotors "may" loose the magnetic force if left on the bench for a length of time if this is not done. But I do not know how much it effects the rotor as I've just lately found this out from people that recharge magnets. I never worried about the rotors before but doing this should not hurt it and is probably better for them.
you can do a search "magnet charging" or "magneto recharging" for more information it may be these magnet rotors don't need this but why chance it(seems like black magic or Voodoo). A lot of the info pertains to old, real old magnetos. Depending on the material the magnets are made of will also matter if you need to do this or not. I do not have any idea what type of steel the china magnet rotors are made from.

Just a thought....I had a motor that showed spark when motor was spun...so i spent the rest of the day going through the whole motor....In desperation I switched out the cdi from another bike and it fired right up....if your friends cdi is handy you might want to try....Just thinkin....anyway I learned a thing or 2 form norm on this thread....ty.....J

Well I guess if the key isn't sheared then. You have spark, fuel getting to the engine. spark plug does fire when tried with it out of the engine.
Your earlier post said your plug gap is 0.025 try 0.017 use a new plug.
A spark plug can throw a good spark when not in the cylinder normal atmosphere
once its in the engine and under compression where the pressure is way higher than the normal
atmosphere it will not fire which may be what your experiencing. Less spark plug gap will allow
the ignition system to not have to work as hard to fire the plug.
You do have the cdi wired right blue from engine to blue on the cdi and black to black.
white wire taped up so it can't ground out.
If you have the kill hooked up you may want to disconnect it until you can get it to work.
If you have a known good cdi give it a try.

A_DangerrX said:

Update: Problem solved! Turns out the problem was the magneto unit. I got a new one, and after I had replaced the old one the bike started almost instantly. On examination, the soldered connections to the coil were of very poor quality; the wires were not actually in contact with the contact points, but were suspended in solder blobs. I'm thinking that the reason for a weak spark was that the flow of electricity was impeded by having to travel through the solder to get where it was going.
Any case, thank you all for your input and assistance! Here's the newly-posted thread about the bike you helped make functional:
http://motorbicycling.com/f26/mopod-mk-iii-66cc-16320.html

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glad you got it solved.... there is alway some one too help ,, enjoy your ride!!!!!

an engine will never operate efficiently when you have a leaking crankcase, jug, cylinder head, check the cdi wires to the ignition coil, as they are garbage wires which become cold and brittle and tend to snap if they are placed into an uncomfortable position, and get a mixing syringe and start off at a respectable 22-25:1 break in mix for the first 3 gas tanks with a moderated throttle amount, then 30:1 for the next 3 tanks with increased throttle action(gentle hills help out on ring sealing) i would not go above 35:1 for an oil mix, for these engines are not precision assemblies(nor can the materials be trusted), too much oil = output inefficiency and excessive pollution...these engines are great and last quite the distance with a proper break in along with maintenance...these engine kits are rudimentary in nature coming from many years of rc nitro engine experience, these engines are very simple to work on, just do not lose faith and patience!!