I should probably have started a new thread as this is a new problem...
My Longchamp now idles fine, and I had it idling for ½ hour without problems today. But then I looked at the plugs, they were all black and dry.
So I started the engine again to adjust idle mixture screws. Nothing happened, I could turn the idle screws all the way in without any effect, I've never seen that before. So the carb must give fuel from somewhere else?
I changed the PV (still 6.5) even though the old one seemed OK, and traced the vacuum path from the PV to the bottom of the carb. And I made sure the secondary throttles close fully (bent the linkage and adjusted the screw from beneath). Same result, perfect idle, but black plugs and absolutely no effect of adjusting the idle screws.
I tried putting my finger on each of the 4 idle bleeds, each time the engine started to stumble. (By the way, there are 2 small holes beneath the secondary throttles, is there an entire idle system there, I thought it was only non vacuum carbs?)
Any suggestions??? If I have the world's only car that can idle wihtout using gas, I'm impressed