50cc, Lost power, cut off every block,hard 2 start By blacraven (Read 2,560 times)

[blacraven]

Hello all, i bought a New Shanghai 2009 50cc scooter 4 stroke about two months ago
about 1700km now, ive had a problem after about a month, i ride(or use to) daily. alot of times with my wife. (total weight about 500lbs, i know, too much)
it was fine until one day we were on it and it slowed down and stalled.. i re-started and it sounded funny like it wasn't turning the engine only a ???spinner??? <not a slipping starter noise, but another noise>, tried again worked fine, this was the begging of it all. slowly but surely over the weeks i started to lose more and more power, it became harder and harder to start. it takes about 10-20 starts and cut offs to warm it up(it wont stay on even with full throttle until it warms up) and then it still wont go past two blocks without slowing down and cutting off. with both of us only 1 block. it will idle forever once it fully warm, rev up fine go around in small circles in a vacant lot but try to go a distance of more than a block and cuts off every block again. i only use sunoco ultra 93 gas, it has never had cheap gas, only the best. i broke down the carburetor fully yesterday cleaned and sprayed everything, but it was already very clean, air filter is clean, i changed the spark plug, it wasn't worn at all, wires look great, hoses look fine, one hose(dont know which, not gas) has a crack but i sealed it and started it to see if it was a difference and it wasn't. i never modded it in any way. the bike is well taken care of, i only put too much weight on it so i think that may be the problem, i use to get it up to 50mph down hill and go pretty fast on a straight away, now i can barely hit 12 miles per hour. PLEASE HELP..
ive searched everywhere and i don't see anyone with my problem, how can i fix it? don't wanna take it to the shop if i don't have to, im pretty handy myself also if i wanna keep riding my wife should i upgrade for more torque or no? and how will that affect my overall lifetime on my bike?, i like the rollers and springs vids i saw, i would love to have maybe a little more speed, but honestly i didn't mind things the way they were before the problems.
HELP!!!
Thanks.

[Alleyoop]

I sounds like your valves tighten up and you do have 1700KM on it so it is pretty much broken in. Hard starting and dieing all point to the valves, so I would adjust the valves.
Alleyoop

[blacraven]

Thanks a million! I dont know what or how to do valve adjustments, or what ill need. is it like throwing the timing off or something? Sorry im a novice but I'm willing to learn.

[ootscoot]

the little 50cc engines have a very small piston and cylinder doin a lot of work - we have seen many an engine wear itself out trying to haul 250 - 300 lbs around...500lbs is probably overloading the poor thing...
but yeah, check those valves

[Bashan]

Here's our tutorial on a 150cc but the procedure is the same, at the end it gives the different gap settings:

SCOOTER DOC VALVE SETTING TUTORIAL

If setting the valves doesn't fix your problem you may need to check the compression, we have a tutorial on that in Engine Tech. Rich

[blacraven]

Hey, Ive adjusted the valves both at .003 to the best of my ability, the one on the bottom was very hard to get to, i have my doubts about that one but i triple checked it and i think its right.
well, ... im happy to say that i effortlessly hit 40-50mph again! its like my bike is re-born, thanks so much everyone that helped me.. i do have a slight problem, i think it has something to do with the bottom valve, im getting some backfiring every now and again. and also is that a good setting to have them at .003?

[Alleyoop]

It is probably running a little LEAN try richen up the Air/Fuel mixture about 1/2 turn. Now that the weather is cooler it needs more fuel, you may have to turn it out more than a 1/2 turn. Try Half turns at a time and see if the backfireing goes away. Also check your Header pipe where it connects to the motor. If its leaking there that will also cause backfireing, Also check your Vacuum lines and around the Intake and where the Carb connects any air leaks will also make it run Lean and cause backfireing. So tighten all your lines and connects to the Carb and Vacuum lines.
Aleyoop