Hi I'm new here obviously.. but my boys bought 2 Kandi spider 150's
They have some electrical issues where they cut the harnesses that I'm
Going to address but 1 buggy will start will go in reverse as fast as it can
But in forward it hardly goes, at first it would go but lacked so much power
Not it will barely go.. any help would be much appreciated

Here's a video I did on the basic wiring for a 150. It might be slightly different on your machine but the principal is the same, https://youtu.be/4U1ZulC22Zc

Your second problem seem to be the CVT. If the rollers on the front clutch / variator are not set in the ramp properly, the CVT will be at higher ratio and give you this trouble. The reverse is geared lower and this is why it work. remove the CVT cover and remove the front clutch, make sure the rollers are set properly and reinstall it. You should also check to make sure you do not have flat spot on the rollers as it will destroy your belt.

Thanks ill check into that..
Another question i have a dazon raider 150 thats upgraded with the transfer case and switched to chain instead of belt and the secondary drive gear is ate up do you know a brand or where i could get a stronger one ill post a picture

Post a better picture of the gear you need and the full shaft. I just checked my shelves and the 150 parts I have does not match what you show.

Post also a picture of the entire machine and also the engine.