Wah, my 34L is driving me nuts. After 25 years of (almost) blameless behaviour, its finally decided to play up bigtime.

Symptoms: starts fine, runs for a couple of minutes, then cuts dead with no warning. Will immediately re-start (first kick), and run again for an indeterminate (but short) time, then cut once more. Repeat 3 or 4 times, then she dies completely and won't be revived for a few hours. Cuts are (usually) accompanied by an enormous backfire (which its never done before).

I was having some grief anyway with a sticky carb float, so have replaced float + fuel valve/seat and blown out all the passages with compressed air. Float height/fuel level is now perfect. Loosened fuel cap, removed air filter to see if there's any strangling of air or fuel. OK.

The 'instant death' symptoms suggest to me that its an electrical fault (there's no gradual leaning off or decline/increase in revs which you'd expect from fuel problems), but I can't imagine what electrical fault would do this consistent stop/start/dead behaviour?

Next job is strip off the wiring loom and check all the continuity/insulation, I guess? Wiring loom was replaced about 10 years ago, btw, and I'm running a big capacitor in place of the battery, if that's relevant.

Any ideas gratefully received!