The indicators light up both sides front and rear. Upon investigation there’s no flasher unit. Bought 1 off ebay. It has 3 wires. A black earth, a brown and a brown and white. Can anyone tell me how to wire it in please. I hope this unit works as the 1st one I bought was completely rusted to pieces inside. So as well does anyone know if there is some where I can buy a good unit. The headlight isn’t working either and I’m dying to get it registered. TIA

If your mounting it in the original location on the bike there should be 3 wires coming out of the wire harness corresponding to the 3 different colored wires coming for the flasher unit. You just plug it in. Is your new flasher a Yamaha part or aftermarket?  Did you test the headlight bulb with power to see if both the low and high beam are working? 

Make sure that you fit a 6v voltage regulator before trying the headlight with the engine running - see attached link. I'm not 100% certain, but I think that the headlight only works with the engine running (happy to be corrected, though).

Vintage Yamaha Enduro Fans - Service Bulletin #M5-084 re Voltage Regulators (yamaha-enduros.com)

I just came in from the garage with a fulll head up of steam. I hard wired the headlight and it works. In fact it's new. I had an auto electrician in yesterday. An older fellow but not too old but he couldn't get either of the 2 flash cans I purchased on ebay to get the indicatos to blink. Bulbs are correct. the earth, brown and white and brown wires from the flash can is pretty straight forward but they just will not blink. So I can't get her registered. I'll try an after market flash can next (out of desperation) but that still leaves the headlight problem. I'm stuck for ideas?

Just guessing, but does the bulb wattage match what's written on the flasher unit. might say 8 watt [or whatever] but means two of 8 watt plus a 3 watt for the flasher warning light. Typically wold say 8x2+3 on the unit. Might be 17 watt in your case in which case 8 watt will glow but not flash. 17x2+3 i mean. Sometimes the have CP for candle power & i "think" 21CP or is it 32CP equals 17 watt. Someone will know.
I'm in NZ down under so flasher units could be different but if it's the big unit like you describe with 3 wires it's likely the high wattage one .

Without the engine running, then a really well charged battery is needed for the indicators to flash.

A modern 2 pin 6v flasher relay will work perfectly well on your bike.

No offence intended here, but do the voltages of the components match up, including the bulbs? The original system was 6v, although 12v conversions are available (probably less common on the 250 than the 360). 12v flasher relays will be different to 6v relays.

If the engine is running, the headlight switch on the left of the handlebars is in the "on" position and the headlight (high or low beam) still won't come on, then I would be looking at the contacts in the headlight switch and the wiring connections in the block connector (I think behind/below the headlight bucket on this model).