So… yeah. I tore down the top end. I re-ringed. I honed. I timed. I reassembled. I attempted to fire. No dice.
A friend who has been absorbing most of my frustration about this project told me a rather involved story about another Japanese bike with similar issues. In the end, it was the ignition controller – what I call the ECU or knock box.
In the Super Sherpa, the ECU controls ignition retard and advance. If the plug is firing at the wrong time, the engine won’t actually produce power, even if it does light off. As I’m getting mixture out of the exhaust, I now know the carb is working. But the funny whooshing noise the bike is making when I take the exhaust off is definitely weird and could be the result of faulty ignition timing. If the mixture is lighting off and blowing out the open exhaust valves…
Next up – check all of the ignition system components.
I already know the ECU is suspect – the pinout fails about 60% of the tests required.
Anyone have a spare Sherpa ECU?