I bought this bike in stock condition 3 years ago and when I would hit about 65-70mph it would bog down like someone was pinching the fuel lines on and off really quick, or flipping a switch back and forth really fast disconnecting the spark plugs - sort of a sputtering behavior. I ruled out a vapor lock in the tank by opening the lid at speed. Strangely this behavior does NOT repeat itself in 4th gear hitting the same RPM, only in 5th gear at 65-70mph. It's definitely not the clutch going bad as proposed in another similar post.
So I thought it might be a carb issue and since I was using this as a donor bike for a custom restoration (see below) I figured rebuilding both carbs would correct the behavior. Unfortunately after total rebuilds of both 36mm Bing carbs with new diaphragms, O-rings, needles, floats, jets etc. and a thorough cleaning the problem persists.
Any ideas?
So I thought it might be a carb issue and since I was using this as a donor bike for a custom restoration (see below) I figured rebuilding both carbs would correct the behavior. Unfortunately after total rebuilds of both 36mm Bing carbs with new diaphragms, O-rings, needles, floats, jets etc. and a thorough cleaning the problem persists.
Any ideas?