Hey guys, I have a 1978 cb750k. Kinda new to bikes but got myself in deep and had to do a full restoration on this bike. Sat for 15 years before I got it. Info: I just finished an engine rebuild, rebuilt the carb, and chopped the exhaust below the foot peg. Compression is good, just reset valve clearance, all cylinders are getting spark, after chopping exhaust the bike had a hard time starting so I turned all the mixture screws an 1/8 turn out. The bike now runs with the choke on. Synced the carbs, 1,2, and 3 have about 14-16 inches of vacuum at 1.5 turns out on the idle screw. Cyl 4 has around 5 and won’t move, sprayed starter fluid all around the boots and nothing changed, so not sure what the problem is there. Problem: First start of the day, the bike runs a little rough, but after about 30 seconds it idles just fine and sounds great when revving, then put it in gear and it doesn’t want to go anywhere. I’m confused how it will idle and rev fine once warmed up, but it can barely pull its own weight. Has anyone else had this problem, or know what I should check to fix this problem. First I was thinking the drop in back pressure from the exhaust was the problem, but after a ton of reading, that would not cause this big of a problem. Could the choke being on cause thins much of a problem? I have not tried running it with it off recently. Thank you to anyone who can provide any advice!!
