I'm not sure if this question belongs in this forum, if not maybe you guys can direct me to the right area or website. We had a DR50 dirtbike that worked flawlessly for 5 years, even the headlight and horn still work. But as soon as I sold it to a friend the darn electric start button quit working so they have to pull start it.
I put a new battery in it, and the charger seems to be giving it juice. When we hit the button it just tries to start for a half second, then nothing. Horn and headlight are working fine as I mentioned earlier.

What else could I replace on this bike to get the electric start to work again?

 

I'm not familiar with the bike but starting systems are pretty similar.

So your starter turns a half second or so and stalls. Take a meter and measure the DC voltage right on the battery terminals while attempting to crank the starter motor. You should see no less than 11 volts DC. Report back what you measure here.

Do the same measurement with the meter probes between the starter input terminal and the starter case while attempting to crank the starter. Report back what you measure here also.

When you report back, keep in mind that vague phrases such as "it tested OK" or "I got nothing" are not helpful at all. Be as specific as you can. There is diagnostic info in those two voltage measurements.

Some more thing to try:

Jump the bike battery to your car (please be absolutely sure to get the polarity right - your little bike battery will lose the contest with your car battery if it gets hooked up backwards. Plus to plus, and minus to minus...). Does that change anything about the starter operation?

Find the starter solenoid posts. One connects to the battery through a heavy wire. The other connects to the starter motor with a heavy wire. Short the two posts together with a screwdriver. A few sparks is OK. Does the starter turn over any better?

Try to start the bike with the starter switch, and hold it there for 10 seconds. Then quickly feel all the connections between the battery positive post, through the solenoid, down to the starter, and along the heavy wire ground return back to the battery minus terminal. If any one connection gets hotter than another then look carefully there. Hot connections are bad connections.