Welcome to Miniriders Brandon,
Make sure you drop in and say hello in our
Introduce Yourself thread too while you're here.
As Snaptrax mentioned above you have 3 options with the broken crankshaft.
First one is to grind what's left of the thread/stub off the end on the crank, then drill and tap the end to accept a bolt.
I would use a M10 x 1.25 pitch x 25mm long 12.9 grade Unbreako bolt, and a thick machine washer, M8 is a bit small.
Buy a M10x1.25 Intermediate tap, a tap handle and an 8.9mm HSS or Cobalt drill bit, a 3mm and a 6 mm drill bit.
The hardest thing will be making sure you drill straight into the end of the crank.
I would suggest removing the engine and set it up in a drill press to make sure you are drilling square into the crank.
Start off with the 3mm drill bit to make a pilot hole about 20mm deep, then use the 6mm bit to open it up, and finish with the 8.9mm bit.
Next way to fix the broken crank would be to replace it with another one, new or good used.
I might be able to help you here, i have a good low hour spare one.
Last way would be to replace the complete engine, a new Lifan 125 engine could be sourced from ebay
NEW 125cc Lifan Type R Head Racing Engine Dirt Bike Motor 4 Speed Manual Bonus | eBay
Or from any pit bike shop, or a used one off gumtree or a facebook buy swap sell page
A second hand engine could possibly have other problems too ?
You could also get a bigger engine and use that too, a 140, 150, 160 should be an easy swap over but are dearer too, the rear clutch engines will need a new longer clutch cable with a threaded end for adjustment.
Cheers, Craig
