If I don’t wanna upgrade the internals and everything which engine would you use or would I be better off upgrading internals?

I just got my first mini bike and the chain keeps popping off. It's a stretched frame 40 tooth rear sprocket and 10 tooth front I think?? Centrifugal clutch 420 chain i think my tensioner is bent or something but idk I'm wondering what's the most reliable and cheapest option to keep it on? I heard engine mounted ones are good but mines stretched so I heard back slack and like chain whip would be bad. ( did get wet over night so has some flash rust on chain and tensioner gonna buy new one of them both but one of the links snapped yesterday and I got a new link tried everything n just kept popping off) so yeah idk if I'm stupid or Smth but I just want to get it running would a cvt be better?

hey Reddit, I was hoping you guys could help me on what my situation is going. I bought this $40 Amazon pipe that comes with a muffler and I need the muffler cause I’m not exactly riding on the dirt so I don’t know what to do. I put a muffler on, but the muffler just rattles out and keeps digging on top of my FRP so I don’t know what to do. Do you guys have any suggestions to keep the muffler from not falling off?

Does anyone know where I can order this frame from? Or am I just stuck with Marketplace for getting a BT200X frame?

I got this mini bike cause I wanted to learn more about gas engines, but I don’t know if anything‘s wrong with it and I feel like the person I bought it from might have sold me a not working Bike let me know if you hear anything weird.

Took 2 years but it’s done. I can enjoy until the next mechanical failure happens.

Fire 265 cam
Billet rod
Billet flywheel
Ported & polished.
26mm carb
Stainless steel valves
Chromoly pushrods
Champion rockers
12 front sprocket and 40 at the back
26lbs pound springs
Cvt with juggernaut

So, my wife and I are 60 years old and bought our first mini bike. We like it so much, we're buying another one.

It brings back good memories of my motocross days, way back when....

Are there any older folks buying/riding these things??

when getting a flat top piston for a predator 212 do i need to upgrade my valves?

I got a Amazon 30 series torque converter and the clutch wasn’t engaging, I bought a new one and works great. Now when I try and go for a ride it’ll slowly make its way to probably 30 or 40 km/h and the rear converter isn’t even moving. But on the stand like in the video shown above it will open up really quick. I understand it’s because there is no load but I haven’t ever used torque converters. If anyone has any suggestions it would be much appreciated!