Scooter won't start - this issue became progressively worse over time

[peonpete]

Hello, as the title says my TaoTao 50cc Atm 50a1 is not turning over anymore. The electronics seem to be working fine - the lights come on, the horn works etc.

The issue is when i try to get the bike running it just makes a slow noise as the engine cranks, it sounds like it is trying to start but it can't.

I have swapped out the starter motor with another start motor and it still has the same issue. I also swapped out the starter relay and that didn't fix it either. I fully charged the battery and it *did* turn over once, however when i tried it later it did not...So i fully charged the battery again and this time it didn't start the bike.

So at this point i am thinking [though unlikely] that it is a battery issue and i am going to test that soon.

If anyone has a idea of what the problem could be please let me know since i won't to get this scooter running reliably...

Here is a video of the sound i get when trying to start up the bike [using the electric start]:

[sc00ter]

How many miles? Service history? Check the valves? A place like Batteries Plus will test the battery for free. If its not the battery then check:
Is something catching in the transmission? I've had a damaged clutch that was hanging up the motor.
Loosen the gas cap and check for vapor lock.
Choke circuit could be bad if its starting to get cold where you are. I'm going thru a hard start issue on a Honda Metropolitan right now.
Check the valves. I'm doing that this weekend just to eliminate that possibility.
Bad gas? The Metro had nasty gas in it. Got out what I could and put in fresh gas.
Spark plug fouled? Electrode looks clear?
Air cleaner good? Does it need to be changed?
Let us know what you find and good luck.

[sc00ter]

And heres a quick note. Dont be a cheap-o and order the cheapest battery from Amazon. I only use and trust:
EverStart brand from Wal-Fart. Had good luck with them. Just be sure to use a gentle charge (2 amps), not a speed charge (higher that 2 amps).
Xtreme house brand from Batteries Plus. Come already changed. Great quality.
YUASA, the real ones. Pricey but good quality.

[Roscoe]

What I'd do. Jump from a car battery and see how fast it cranks. Check the cables both to the relay and the grounding cables. Check for warm or hot spots on the cable after cranking. Check voltage drop at various points of the starter circuit when cranking. It sounds to me like you need a new battery but other things can cause slow cranking. When the starter is off you can usually tell a good or bad one by the way it "kicks" when you attach jumpers to it from a car battery. You can take the spark plug out and see if it cranks faster to try to eliminate if some thing with the engine/drive train is causing it to crank slow. But I'm think a new battery and good cables will probably solve your problem. Be careful when jumping or cranking excessively with a good battery, you will overheat the starter and ruin it.