G'day Bondy,
The original engine was wired so that the engine was stopped by the ignition switch. You now have a different aftermarket engine that has the engine stop (magneto) controlled by the throttle lever. This can be altered by modifying the wiring behind the fuel tank as previously discussed. If you end up refitting the seat switch (as you should) this will need to be done eventually anyway. The suggestion that you leave this for now is so you can tackle one problem at a time.
Of course the stop/choke issue will need to be resolved. Have you had a chance to look at this yet?
How are you going with the rest of it. You should be close to power up?
