It should do better. You should get close to hitting the rev limiter.

 

When I shift up it stays at 38 but just in lower rpms. Ill get a replacement plug tomorrow.

 

Don't some of these bikes have rev limiter in the lower gears? The FI ones? or?
I can't read the rev's. He can't be in 6th as his Rpm's would be much lower.

 

Earlier in the video that I had to edit out because the camera came loose, I shifted into 4th and it stuck at 38mph but at 4000rpms

 

I don't think it is the plug. It sounds like it is firing fine, althought there is that screaching sound???

I would suspect the carb (slide mafunction) or electronics.

Did the bike ever run right?
The previous owner did something to it.. or not, regardless, it is very difficult to figure out what is wrong without some major removal of parts. My suggestion is take in to a 'real' shop and let them figure it out. I doesn't sound like your up to the task.

 

Are you sure you didn't buy an KDX 80?

I have nothing to add, but I'm curious to what this turns out to be. Definitely head scratching.

 

That screeching sound is not there, just the camera mic going weird on me

 

I rebuilt a 2004 125 ttr so I am able enough to fix it up if I know what is wrong

In other words, I know how to fix it, just not what to fix. Still an amateur for troubleshooting

 

IIRC, yes the FI units have rev limiters in the upper three gears. Not sure where it limits, but this bike has a carb.

 

You picked a fine project to get some experience!