Darren: Try this when It does that (stops) pull the plug as quick as possible (while still hot) or have a spare plug and hook it up. No spark then its coil and condenser if you have spark then start looking for a wire that my be braking down, shorting out. Possible sparkplug wire problem also! Quick way to tell is start it up after dark and see after it runs for awhile if spark is not jumping around some place!!!
Pops
Pops