Immediate obvious issues were a slight leak from the heated manifold brass threaded core plug. Extremely worn brass throttle actuators, worn throttle spindle and spindle guide. A couple of cracked flexible drive discs, slightly seized jets and seized screws on the one carburettor that was least shielded from the exhaust manifold heat. This is as well as 30-50 years of the usual grime and dirt. First job was to order full SU service kits from Burlen. In addition to this I ordered an extra set of insulator manifold mounts to help cure fuel vaporisation issues. Starting with the manifold and leaking core plug; once removed, threads were damaged on both core plug and manifold but after a couple of weeks of trying to find the correct solution I found that 3/4 BSP thread to be similar yet slightly oversized suitable match. I then tapped the manifold out to 3/4 BSP whilst turning off the damaged thread on my original core plug which I then sleeved with a 3/4 BSP male thread and silver soldered (see pic). This resulted in a perfect fix and looking very original. The carburettors had a good strip down clean, as you can see, the seized screws put up a fight. Once dismantled, the state of the jet return springs was a shock, but I think possibly heavily corroded from modern day ethanol rich fuels. Obviously all jets, return springs, and seals etc were included in the service kits. To clean up the parts prior to reassembly I put together a home made soda-blaster by using a shults gun (underseal spray gun) and a 5 litre empty bottle to hold soda. This works a treat to clean the aluminium parts without being aggressively abrasive. Next, was to tackle the brass throttle actuators. I filled the worn holes with brass plugs and silver soldered to blank off the worn holes before redrilling to original diameter. Also, as you can see in the picture I filled worn throttle rods which locate through these holes with solder and then filed back to original diameter. Throttle spindle I replaced with a standard metric stainless bar and replaced the cracked flexi drive discs. To repair the worn spindle drive I had no option but to sleeve with a bronze bush which worked a treat (see pics). All these works have resulted in a beautifully balanced action and opening all 3 carburettors in perfect harmony. If you take a look at the air filter box you can see how I managed to match K&N filters to replace paper elements which although sounds slightly more boy-racer it's actually far more consistent with an original period filter. Early filters were washable and reusable and the K&N has the benefits of allowing even more air flow which these thisty triplets appreciate immensely. Posted by Hewitt OPC 02/03/2014 11:09:56
