We just got our son one of those Razor MX350 electric bikes and I have to say that at first when we got it I was quite happy with the bike in most categories but I was certainly displeased with the run time on the batteries. It seemed like you'd charge it all night and when my son would go out and use it, barely would go for 10 minutes before dying and he's only 50 lbs. Now I thought this was a bit strange to have a constant low batteries because we have an electric car he uses and he could drive that thing for 30 minutes and the battery in that has fewer amp hours overall to boot.

Hopefully this helps someone else who might have gotten one of these I looked at replacing the batteries because I thought they might be defective. During my testing I found that the connector seemed to change from charged (green) to charging (red) just by wiggling the charger's connector. So I first looked at the pins on the bike side connector. I opened them up with a small flathead screwdriver to make better contact with the connector. I tried the charger's connector again and found that while it did feel like it made much better contact, it still would change charge status when jiggled. Finally I took apart the connector on the charger side and found that both of the pins were very poorly soldered inside and one side had become totally disconnected to the point it was obviously just making random contact (Aha, now we're getting somewhere!!!). Breaking out the soldering iron I redid the inside of the connector and set it to charge again. WOW, finally the machine was as it should be and lasts the full 40-60 minutes as advertized even when used hard.

I also took apart the rear end on the bike and cleaned out all the nasty low quality grease they used in China to make the bike and reapplied were necessary. The worst drag was on the chain freewheel, the band brake and the chain. I used a synthetic bike chain lube for all the above mentioned parts and it works great now. Overall I definately recommend it if you have little ones that like electric vehilces and can ride a bike with no training wheels.

Here's a pic of what we got him and what to do with the charger/connectors: