I’ve been consulting this forum daily for a few months now and have found it very informative and helpful. I really appreciate the fact that something like this exists, thank you. I realize this is a long post and probably a pain to read I just wanted to be thorough. I have very limited mechanical knowledge.
The bike is a 1974cb550k. The engine appears to be partially rebuilt as some parts have what appears to be yellow junk yard paint on them. It has 33K miles on it and vins on the engine and frame are different. The four exhaust pipes have HMCB500 SR HM323 inscribed on it, one of which has rust holes. The PO told me that the 74 550s shared the same exhaust as the 500s, thus the CB500 inscription… is this true?
Anyway, On the first day I got it it seemed to drive well for the first 6 miles but then slowly began to stall. I was able to start it back up and drive it for a few yards but it would eventually stall after a minute or so. I assumed that it was a fuel starvation problem. The tank had rust in it so I cleaned it out a bit by shaking a handful of washers around inside of it with distilled water, rinsed it out with gas a few times and got most of the crud out. I removed and cleaned the petcock, and replaced all of the gaskets inside of it because it was leaky. The petcock bowl was completely filled and hard packed with giant pieces of rust that I needed to pry out with a screwdriver. I added inline fuel filters and the bike would start but would still not idle properly and would stall. All cylinders seemed to be firing as the pipes were equally hot. I put in new plugs, same result.
I began to assume I had carb trouble and was reluctant to dig into them myself so I took them off and brought them to a guy at a small shop who said he would clean them for $40 and let me watch. He only took off the bowls and soaked the main, needle, and pilot jets. He had to really pry out one of the float hinge pins with pliers. One of the pilot jets was clogged so he gouged it out with a piece of wire. He blew air through all the passage ways, put them back together and said they should work. I put them on my bike, started it up, and one of the carbs wasn’t getting gas. Also the tops of the bowls were leaking gas and he put them on out of order so I couldn’t get to all of the drain plugs. I took the carbs back off again and discovered that the dry carb had a stuck float that wouldn’t budge due to an extremely bent hinge pin. I took out the pin, straightened it out, and had to sand it a bit to get the float to move freely. I also noticed that the main jet o-rings were all extremely worn and would move loosely when seated. I unfortunately can’t afford to buy 4 rebuild kits so I bought metric o-rings from a local shop and meticulously sanded down the OD of each to fit them in. I set up this ridiculous contraption that involved mounting my gas tank on top of a stand and suspending my carbs in the air with string without the bowls on so I could test to see if the float needles were operating correctly and allowing/prohibiting gas into the chambers. All appeared to be in working order and the float levels seemed ok. I put the bowls back on with new gaskets and put it all back together again.
Now when I start it up it will only idle with the choke opened slightly, when closed it dies. My question to the board is where do I go from here? The mechanic that cleaned my carbs said that he didn’t need to sync them because everything looked ok to him. However, I doubt his competency due to the fact that he put the float hinge pin in bent and the bowls on in the wrong order. Should I pull the carbs off again and attempt a bench sync, or should I look at something else?
