NEVER RIDE A MOTORIZED BIKE WITHOUT 2 BRAKES!!!!!!
I have the handlebars down to a simple science for those bikes.
Step 1. Strip EVERYTHING from the handlebars.
Step 2. Get a SickBikeParts 'teeter-totter' dual brake lever.
Step 3. Either remove the cable to your front derailleur or remove the whole darn thing.
Step 4. Assess you rear derailleur controller..
Is it a simple twist with it's own mount? Or does the brake lever attach to it?
If it attaches to brake lever you will need a twist or the old lever kind.
Step 5. Put your dual pull brake and then throttle on the right.
Step 6. Put your clutch, then the rear shifter control (it will read upside down but work), and a short grip on the left.
Personally I don't use kit or existing bike grips unless they are the kind that can stretch, specifically stretch over a throttle barrel.
For the most part they don't so I use BMX foam grips on both sides, they will squeeze over the throttle.
When you are done you have something like this.
If you want to change the chain on your front sprocket just move it by hand, otherwise you have a fully functional and SAFE ride!