Welp, failure to launch, but damn does it look good sitting there. I'm not quite sure why it's not starting up. My guess is either the oil level is too low or not enough air is getting from the carb to the cylinder. Any guesses?
I am wondering if the low oil sensor could be shutting it down? Un-mount the engine and place it like it is suppose to be used (horizontal) then try starting
it. I would suspect that you filled the engine with oil sitting horizontal then mounted it in a sharp angle with the seat post mount and the low oil sensor on
the engine? That would cause the engine to be shutdown. Minibike owners usually remove that sensor since it causes problems offroad. Make sure the
plug is not wet with fuel, you have spark, the red shutdown switch is on for spark from the mag. A good aftermarket aluminum intake manifold should be
used to be sure there are no vacuum leaks. I can't tell by looking at the image which needs to be a closeup on the carburetor an shutdown switch wiring.
When running a Mikuni carb on first startup cold, always crack the throttle a little bit and then try pull starting the engine. You should have the rear
wheel off the ground just in case the engine starts in a high throttle position. Is that a Mikuni copy or a real slide Mikuni which uses the fuel enrichment
lever much like a choke for starting the engine? A wet plug could be caused by a float valve sticking open which should show up on the fuel bowl vent
with an overflow. Check for spark first then (that eliminates switch shutoff). Note, a compression release on this engine could be a problem so you can't
really check the compression properly on this engine with a gauge. A slow easy pull on the pull-start rope should let you feel a good amount of
compression on the engine. I might also add, the intake gasket has to be positioned right concerning the engine and intake manifold, otherwise you will
have a vacuum leak and there's a way to get it on backwards! A lot of variables to check on.