Guess what... I did the alcohol thing anyway. Still friends?
The bike is an 81 CB650C. I'm reviving it for a guy at work. It sat, unprepped for a year or more, outdoors. The brake pistons were rusted to the calipers. There was no air filter ("Is that bad?" the owner asked!), etc, etc.
You may be right about the sticky floats. After doing my crude needle test, and before phase II, in progress now, it took the bank of assembled carbs and turned them over and over, listening to them closely. When turned right side up, I could hear the floats drop, but when turned upside down, no sound until I gave 'em a gentle shake and then I could hear them drop.
So, next step, I stuck a tight fitting funnel onto the bank's intake pipe and slowly poured alcohol into it. I'm attempting to either fill up all four bowls and hopefully the alc will back up into the funnel and stay there, confirming that all needles are seating. Maybe it will over flow and I can get a better idea where it's getting out.
Right now, the bowls seem full, because I pour until the alc backs up about 1 inch into the funnel and stops, or seems to, but really it drains VERY slowly, taking about 5 minutes for that 1 inch in the funnel to drain. I'll keep doing this until I either find a leak, or until the alc finally backs up and stays there. The rack is on my bench, and I've got a spotlight, so I can see there are no leaks yet. Eventually, one of the two possibilities much happen, right?
Regarding dirt in the fuel line, I did think of that. I sprayed carb cleaner through the new fuel line I used for testing (see below) and used a fuel filter before using it to supply fuel.
Here's what went on a couple of nights ago (from an earlier post):
I disassembled, cleaned and reinstalled (w/o the airbox, for testing) the carbs of a 1981 CB650C. My aux fuel tank is a funnel suspended about 18” above the motor. When I added fuel, it began flowing out the rear of all four carb bodies. When started, the engine raced at first, then settled down to normal. I added a little more fuel to the running engine and it began racing again.
When I cleaned the carbs, the floats and needle valve looked good, and I find it hard to believe that all four failed simultaneously. Could it be that the pressure of the fuel coming from so high up was able to force it past the closed needle valve?
Also, this bike has a very odd petcock. The petcock itself is the normal older on/off/res type, but the fuel then flows to the vacuum shutoff valve which is mounted on top of carb #3, after which it then flows to the carbs. I left this off intentionally but am now wondering if the diversion and subsequent U-turn also serves to regulate the fuel pressure. Comments?
TIA,
Tim
