Originally Posted by
fyrstormer
Tampering is modification with negative intent. The engine was misbehaving and I modified it to improve the misbehavior. Changing the taper on the LSN caused a moderate improvement in the stalling-after-idling problem, but it wasn't enough on its own. After I dialed-in the HSN setting and before I modified the taper on the LSN, the engine would idle happily for several minutes at a time, but even if I very carefully opened the throttle, the engine would cough-out huge puffs of oil smoke and be unable to rev-up. The obvious interpretation is the LSN was severely rich, but a severely rich LSN setting would not allow the engine to idle happily for several minutes at a time -- a severely rich LSN would cause the crankcase to load-up on unburned fuel and choke the engine, which is not what was happening. (yes, I did in fact open the back of the engine to check for excess unburned fuel after letting it idle for several minutes. There was no unburned fuel; only a few drops of oil.) The taper on the LSN wasn't progressive enough and it caused the fuel mixture to enrich suddenly when the LSN was pulled out of the fuel feed, quenching the glowplug and preventing proper ignition.
If it doesn't die but it wont rev up you have to lean the top, the bottom does nothing for high revs. Also, proper way to tune is, you get the car to launch nicely, then you tune the top to get RPMs. Then, once its running nicely and making good power, you fine tune the bottom and idle. Most people, in racing at least, tend to run the bottom too lean, I learned that the hard way. You want the car to be a bit sluggish on the bottom until the fuel clears, once the motor is up to temp it will make power, top AND bottom.