Thanks Harry for quick reply. Burlen did the job and it looks very good. The piston clunked when I fitted carb some while ago. I will remove filter and have another look. I have had the head refurbished and it now runs on unleaded petrol. Perhaps I need a different needle jet combination ?

I used a Suzuki GT750 coil with integral HT lead. Maplin have a black plastic box that the coil fits perfectly.
I mounted mine on the horizontal bracket under the seat. The HT lead is just the right length to reach the distributor
without getting in the way of the oil filler cap. I used the Maplin ...

My 59 SQ4 with fully restored SU carb runs rich at tickover, which sounds lumpy. Low speed running on light throttle openings are not smooth. The jet nut has been adjusted from two turns open plus or minus one turn in stages. The engine starts first kick without choke. The ignition is by electronic ...