so, 3 pages, and not one thread with solid advice on actually diagnosing the problem?
start with the basics. ignition. how to test?
theres spark? good. now take the freaking carby off!
pour some gas down the hole, and give it a spin...if it fires, how simple... what has changed? oh! we removed the carby! so the carb is the problem. or fuel flow to said device, which can be isolated to the filter, the hose, the tank cap not venting, yarda yarda. in the carb? jet, needle, airleaks and fuel height.
you clean the carb, but do you stick a bristle from a toothbrush through the jet and ensure its clean? hold it to the light and see its a fullcircle?
it didnt have spark? start finding out why. too many threads on that topic!
it had spark, no carb, yet didnt fire on raw fuel? then either the magneto rotor is on backwards, has no key fitted at all(ie, a TIMING issue) or, the crank seals are bust. seals are easy to pick by filling the crankcase with petrol... or something less flammable for safety. water. washed out immediately with alcohol, then oiled up again to stop rust.
forget about all these silly little upgrades, forget about throwing money at something you dont want to use...(its for your son? well...make sure he wears a helmet, knows the road rules, and behaves himself! or we will all kick his butt, and yours, if you get it going) and just start with the basics.
i may have posted this a long time ago, yes...its rather dated, and i dont have any newer videos due to me having the same type of experiences with china electronics as youre currently having with china bikes
not so easy to fix, unfortunately
a STOCK STANDARD SKYHAWK 48cc, with ONLY a tuned pipe.
no fancy CDI. no portwork. no beefed up mikuni vm34 carb. no reeds and no freaking PROBLEMS! in fact, the only HT ive never fiddled with! ever! mainly cus the skyhawks build was so superior to anything else i came across, and i want to see how long it lasts. (also the only one i bought and who knows where i got it from anyway? not i, that is fo sho!)
note; not all these engines are the same! ive had awesome, standard and complete POS cr4p that was simply a waste of time. price has had little or no reflection on quality, either!
boiling fuel when it was running sounds like, as you said...really hot, and that is not normal. me myself i, i point my finger directly and very firmly at the o-ring you installed, or a waxy deposit in the jet.
