How do you fix SU HIF's? You send them to Rhys Kent (http://www.sucarburetors.com/), that's how. They now work just fine. The throttle shafts were leaking (new seals were not the answer) and the decel valves had weak springs as predicted. The bushings were replaced with the stock SU replacement part (as Rhys does to all his carbs) and the decel valves were soldered shut with some very nicely fabricated block off plates (copper). They will now hold a consistent idle and are simple to tune -just as the manual describes. Lucky for me my throttle shafts were fine and only the bushings were toast.

So for those that are looking for the solution to their SU woes, this tread serves as my testimonial. A little wear on the shafts (10 to 15 thou) is too much and decel valves that are 40 years old are a bad idea (probably a bad idea 40 years ago). I tried spraying carb clean, quick start and every thing else in my garage (propane etc) and I couldn't detect the leaky shafts. There is enough springs and other junk in the way that this may be the reason why there was no leak detected, it may also be that they were so far off, that a little more "fuel" made no difference to the idle!

Off idle response is very quick, and they return to idle very nicely. I can't say much about the economy as I've been "breaking-in" the engine. Rhys was very willing to work extra hard on my project as I had a tight time line (under a week). This sort of dedication is exactly what we need to support around here.

Craig