Aye Gareth,
Did you twiddle the slow running jet and throttle slide screws?
Did you record what their settings were as you undid them?
Use the base settings for the SZR660 if you have nothing else to go by.
You should also note that these singles can be a bit 'cold blooded'! From cold, full choke, NO THROTTLE and the petrol tap on 'Prime' if vacuum operated. The motor should fire up and run at about 2,000rpm.
I reduce the revs to ~1,500rpm by closing the choke to approx. half open.
Turn the petrol tap to 'Run' and then apply a wiff of throttle, it should take that and be able to hold it at 2,000rpm. Gradually, shut the choke and use more throttle as the engine warms.
Alternatively, jump aboard and ride off, after about 2 - 3 miles, close the choke and use just the throttle.
If this doesn't help, is the choke plunger seating correctly and sealing in the body of the left hand carb? These can sieze due to corrosion and will need 'PlusGas A' or similar to free off. Clean everything and re-assemble according to SZR660 manual.
You are not alone, I have all the suspension dismantled on the Bros at present, new rear monoshock installed and the front end partially rebuilt. The brake caliper at the front also needs some attention!
Good health, Bill
