I have a 75 cb550 with 20k miles on it. I put 12k of those miles on it since I bought it nearly 3 years ago. Prior to that it was in a climate controlled garaged and was kept in running shape since 84 so it never sat unstarted for any long period of time.
Well it started to develop some clutch rattle at idle(1100 rpm) so I figured it was time to sync the carbs. They hadnt been re-synced since it was built judging by the yellow torque paint that was still on the adjuster screws. I adjusted the valves and also installed a brand new dyna-s ignition and made sure the timing was set before I synced it. It was running great at this point, just that nasty clutch rattle at idle. I tried to sync the carbs using an alternate fuel source which was a funnel with a tube running to the fuel line. Thats where I ran into problems. This bike has a 2 valve petcock, one feeds the line for 1 and 2, one feeds 3 and 4. Well like an idiot I only had gas running to 3 and 4 since other bikes I had worked on just had one line for all the carbs. Without realizing it, 1 and 2 ran out of gas and I continued trying to sync the carbs wondering what the hell was going on. By the time I figured out what was wrong the carbs were obviously way outta wack.
Round 2 and I have the seat off and the tank accross the frame where the seat was and extended fuel lines so all the carbs are getting gas. Using a Morgan Carbtune I ballance the carbs...but it still aint running right. I lick my fingers and touch the pipes real fast and find that #1 is cold. Obviously my sync is again out of wack since I tuned with a dead cylinder. Now on to figuring out why its not firing.
I have spark. Did the old spark plug against the block in a dark garage and saw a fat blue consistant spark. And it cant be a coil or timing situation cuz that would effect #4 as well, right? On to fuel.
If I run the bike for a minute or two, on three cylinders, and pull the #1 plug, should it be wet with gas providing it is getting gas but not firing? It seems pretty dry and doesnt reek of gas. Actually looks like it has a tiny bit of oil on it. Normal blow-by I hope?
I opened the float bowl and it had gas in it. I let it drain completely then turned the fuel on with the foat bowl drain still open. Definitly getting gas to the carb. I went ahead and pulled the float bowl(carbs still on the bike) and was able to pull the float, float needle and jets. Everthing looked clean, as I expected, but I went ahead and sprayed with carb cleaner and compressed air for the hell of it and put it back together. Still nothing on #1.
Im going to rule out compression since I really doubt It could have lost it durring this nonsense, and call it a fuel issue. What do you guys think?
Oh yeah, #1 does respond to sync adjustments, even though its not running, and I tried raising the vacuum on it to see if mabey it just didnt have enough vacuum to draw fuel but it made no difference. Is there something simple Im missing? Any ideas are welcome. This ones got me confused and fightin pissed!! Thanks.
