Suzuki TS185 '76

This bike came our way a year or so ago & has been sitting waiting for attention for the past few months as other projects (& the cold weather) got in the way...
It came as a runner & was largely complete. The downside was that there was evidence of some amateur hacking to the wiring!
However a quick google search came up with this excellent diagram which was pretty much the same as our bike, save for a couple of colours being different
http://upload.wikimedia.org/wikipedia/commons/2/23/TS185_Wiring_Diagram_new.jpg

A couple of days with a multimeter traced the problems... The headlamp is designed to work only with the engine running & there is a resistor to absorb the excess output from the alternator when the light is switched off & thereby preventing the battery from being cooked. Not an unusual system on classic motorcycles with un-regulated charging systems, but it does take a bit of logical thought to work it all through & fault find.
The problem with the light was traced to a wire on the lighting coil having come un-soldered...

The MOT was passed, the only remaining problem is to find out what's causing the "flat spot" as the revs are increased to around 5k...