Here's my 2 cents worth of experience. I found a problem on my friend's anglia tripower. Would not idle below 1200 rpm. With it running at high idle, with the air cleaners off, I placed my hand over the top of the rear carb and felt vacuum. At the same time, the engine speeded up. Removed my hand from that carb and went to the front and the same thing happened. The throttle plates on front and rear carbs had been messed with and were not seating properly as another member mentioned. If I would cover both front and rear carbs, the engine would idle down like it should due to the vacuum leaks being covered. The solution? We sent both carbs to a shop in Peoria Illinois where the experienced guy sealed the throttle plates and that was the fix. Anyone want his phone? PM me if u want it.