I've seen the large base cap washer made so the ID was too small.........this effectively blocks off the pilot circuit all together thus it runs briefly on the rich mixture due to tickling the bowl, then it quits due to fuel starvation shortly afterwards........this sounds like your symptom.......the black rear plug could be due to the rear bowl level being too high.......perhaps rotate the carb on its spigot clockwise a little to lower said level.........worth a try if it helps........cheers.......Greg.
The Amal parts illustration I have does not show what I'll call 'the bolt that holds the float bowl on'..I tried to start
the bike, no luck, so removed the rear float bowl, took off the top and no fuel in it and I KNOW I had just tickled it
minutes before. I looked at the arm that is attached to the float bowl and sure enough there was a knackered washer
flattened out in the bottom boss, where the aforementioned bolt goes through. This bolt has two holes in it that
are parallel to the ground, and the center of the bolt is hollow. It appears as though one of the two bolt holes is
supposed to line up with the smallish hole that is in the arm, to allow fuel to run through it. The arm has a very
small bolt in it on the outside I'd never removed, and wondered why it was there. I scrapped the old washer off,
and it was definitely covering up SOME of the hole in the arm. Thus I wonder: How was I able to tickle the carb
and get fuel to spill out. Then again the feed hose is at the top, so fuel could enter the float bowl, possibly fill
and spill out as it is supposed to. Then too, the rear carb was still leaking at the bottom bolt. I was just too
knackered to put it back together tonight and try to re-start. But, I think (we) have found the problem. I found
the flattened washer this afternoon and then came home and read your response, so I sure hope you (and I) are
spot on. My question is: Do I remove the tiny bolt from the outside, line up the hole(s) in the bolt so they are
in line with the hole in the float's arm? That seems to be the reasonable solution, however since there are only
two holes in the bolt hole (not four) it seems as though my tightening process will have to line up the holes
when the bolt is tight, and/or one may need an extra washer on the bottom of the bolt in order to tighten
it sufficiently so it doesn't leak. At any rate, seeing the flattened washer was phenomenal. I have cleaned the float
bowl time and again and paid little or no attention to the round boss on the arm that holds said bolt. Your explanation sure sounds as reasonable as any I've ever heard. Will bolt the plot together tomorrow and see how it goes. Lord-love-a-duck, if this is the problem I'm blessed. You're just right..she ran beautifully momentarily and now I think I can see why she ran out of fuel. Thanks so much. It was just my luck to see the flattened washer, but you would have saved my bacon with your diagnosis. You've sure been there and done it. Here's a pic of the bolt, the bad washer and the tiny bolt that goes in the end of the arm. The washer was completely inside of the boss and at least half-covering the feed hole to the float bow. I was SO surprised the float bowl was empty. For years I have always shut the taps off and run the carbs totally out of fuel when parking the bike for a few days, and it takes a few minutes for the machine to use up all the fuel in the float bowl, so I knew something was awry in the feed and found the flattened washer.