Please hlp wit gp rsr brand new actin funny

so basically ive had this bike since 11/03/09 maybe less than 45-47 mins driving. I read the manual and for new bikes dont full throttle till atleast 3-4 tanks so i did now ive had complications with the chain staying on, ive tightened it with a little bit of play and still came off 2 other times, i took it to a local shop and got the chain and rear sproket replaced because it got bent. Then all is fine for a day, and then today i slowed down for a bump and at about 6-10 mph it started to slow down and kinda locked up, I stopped inspected *** was going on and the chain was a tad bit looser, i procceded to drive very slowly and was very sluggish for about 10 -15 feet and began to act normal until for maybe the length of 3 football fields and did the same thing. I stopped and checked and again chain got more loose, i kinda reversed a bit and tried to go slow and it seemed to work till i reached the destination could it be the clutch drum / Pinion Gear?

i really like the mini bikes but it seems to already be dying srry or the long msg lol thanx in advance

What I do to make sure my chain is lined up is use a metal ruler or straight edge. I loosen the rear wheel and the engine mounts a little, thread on the chain, then begin adjusting both engine and wheel until the flat edge of the ruler lays flat all the way across both pinion and sprocket. If the ruler only touches the front or back edge of the pinion or sprocket, then your chain won't line up. Also, use the adjusters on the rear axle to help keep the chain lined up right.

Don't give up on it - all these bikes need tweaking and tuning to get them set up right .....

Make sure the bolt that holds your rear swing arm to the frame is tight. If your rear swing arm moves side to side that is bad ! You might have to use some washers to shim it.

Do everything like spyguy said, but after you tighten the chain, sit on the bike ( so you move the rear suspension ). Then check how tight the chain is, you might have to adjust it a little bit because of your weight moving the rear swing arm / suspension.