more torque

[bobbykey]

Ive got a chinese youth 50cc atv automatic the motor says BMX on it .

The problem is its too weak on take-off .Is there any changes I can make to get more take-off power?top-end speed doesnt matter It will be set to go about 5-8 mph .

[2004exrider]

if you can find a K&N filter, take your airbox lid off, and an aftermarket exhaust for it you should be set. If its chain drive, drop one tooth off the front sprocket and it will take off a little better.

Jimmy

[2muchquad]

chances are if the rider is too heavy for the machine(read adult)the stock clutch isnt set up for that,some heavier springs for the clutch will raise the engagement speed and the motor will be making more power by then.exhaust and gearing changes will help as well:)

[bradrenea]

How are you limiting the top speed to 5-8 mph? I am assuming it is by the throttle cable adjustment?

[bobbykey]

Yes , theres a screw that keeps rider from going full throttle.

[bradrenea]

Well, with the throttle turned down it's going to be hard to get more bottom end power out of it, with the exception of gearing it down. You should also be able to play with the clutch springs and limit the top speed that way. I don't remember whether it was the primary clutch spring or secondary clutch spring I changed on my polaris one time, but it had all kinds of bottom end but would probably not go over twenty mph. (This was on a 325cc trailboss)
If you add a pipe or filter its probably going to raise the powerband, which will take away from the bottom end power. Then you'll turn the throttle limiter screw in to compensate for the increase in top end power, and you'll have less bottom end power than when you started.
If it were me I would contact one of the shops that specialize in mini quads and they should be able to tell you what springs to change to do what you want to do.
If you can limit top speed through spring changes or sprocket changes you can turn the throttle back up which would also help with take-off.