It would sure help to know exactly what bike and motor kit you are using.
I can take a guess though, did you use an $80 Huffy bike from Wally World (Wallmart)?
That's sure what it looks like, seen it time and time again.
If it's not then disregard the following.
Now you'll have to buy a new back wheel and put hours into transferring the sprocket to it and it will still be a crap bike that has cost you more than a good bike to start with.
Fix it? Come on, as the old Kenny Rogers song goes 'you got to know when hold 'em, and got to know when to fold 'em' ya know?
My only advice is just go buy a good quality bike and move the whole motor kit over to it and toss the POS in the trash because no matter how much you try to polish a turd it's still a turd.
Am I using a walmart Huffy? **** yeah.
Do I give a rat's ass what you think? **** no.
Am I going to buy a new wheel? Nope. I'm going to make this work. Unlike everyone else, I have a habit of taking the hard road that no one else takes.
The funniest thing is that, until here just recently, all the problems I have had with my gas bike were related to the ENGINE. Not the bike itself. I've flipped this damn bike over a curb at 15 mph, I expected the fork and front wheel to be trash. Were they? Nope. I had everything fixed on the bike within 10 min.
Would I have liked to have bought a quality bike for this build? Well, yeah. That would have been nice. But why should I buy a bike for $300 to slap a $200 engine kit on it only to have something on the bike fail catastrophically and leave me broke? When you're 17, get paid sub-minimum wage and sometimes not at all, have a $200+ dollar per month insurance payment, and have to pay for your own gas, you really can't be throwing around a sh1tload of cash on a hobby such as this. Which is why I bought my Huffy (which was $100 mind you).
So, long story short, just as your mother should have taught you, if you don't have anything nice to say, don't say anything at all. I've done most of my research, I knew the problems associated with the walmart bikes (save for the unsuitable grease in the hubs) and I was willing to take that chance. And you know what? It's my bike. Not yours. So why should you care at all? I mean really. If I want to paint my bike a lime green with a gold leaf, I can, because it's mine. And that's all it is.
Thank you for your time.
*EDIT*
And why is a Biblical word edited? Seriously.