I recently purchased a kz750. This is my first bike so i do not know much about it. I am confused as to what year it is because the head tube reads 08/77 but it is titled as a 79. Anyways, when i bought the bike the previous owner said it wouldn't idle. I got the carbs rebuilt, as the previous owner suggested and everything was running fine until I took a 50 mile trip. On this trip my bike started running on one cylinder as i was getting into 4th and 5th gear. Now that it is back i can't get it to run on both cylinders other than in 1st and 2nd gear. Has anyone encountered similar problems or does anyone have any advice on what to check?
I assume it's a 750 twin? If it truly is running on one cylinder, it's likely carb problem. Has the fuel system been cleaned? You have to clean the tank/petcock and install good inline filters or sediment will run down and clog te carb's jets which will make the engine suddenly run like crap.... guess how I learned that.
You should check valve clearance and compression. If it has the original coil, that's the first part I would replace. You can get one from Z1 for $36.
