Rough Idle

[Dave-2]

I just bought a 1980 CB750F Super Sport (18K miles). I want to get on the road but it really idles rough, then stalls. I can handle this by increasing the idle but then it idles much too high, 2500 RPM. I usually work on my bikes myself but I am about to take this to a dealer. The bike is from upstate NY and I live in central florida, could it need a change in jetting, altitude difference is not that drastic but could the change in location require updated jetting??? What would anyone suggest as a starting place???

[gonebiking-2]

Get the carbs cleaned out thoroughly, and then get them properly retuned using four vacuum gauges to get the carbs set up correctly. Turn the idle mixture screws in all the way and then back then off one and half turns. Some fine tuning of the idle mixture scews will then get it running very smoothly at 1000 rpm +/- 100 rpm. No need to adjust  or change the jets for such a small increase in altitude. Have had mine from sea level to 8000 feet above sea level and never missed a beat. Pulled strongly thoughout the rev range

[CB750Winger]

  I agree with gonebiking, clean them out real good and your idle circuit may be gummed up or sucking up crud. Also make sure all the plugs and wires have strong spark. Check for air leaks on the intake rubber, spray WD-40 on them with the bike running to see if there is a change but I would say start with the dirty carb idea first.

[Dave-2]

Thanks to the respondants. I have a chiltons manual so there is some guidance. I want to get high performance plug wires and check the spark plugs (if needed). Can you folks tell me where to get some good high performance plug wires??? According to the manual, you do not have to pull the tank and other parts off to remove the carburetors, what is your opinion(s)

[CB750Winger]

  You might not need to take some things off, but in my opinion, it's easier to pull the tank, covers and get anything out of the way to get the throttle cables and things off and makes it easier to access and see what you are doing. You may even lose less blood this way. Also check the screen in the fuel valve.    Just my opinion            Paul

[Dave-2]

As you can tell, I am trying to do as little as possible but that will proboably reflect in the finished job. This bike only has 18K on it ans now I am wondering if that is because the darn thing just never ran right. Rescue a bike from upstate new york and give it a nice home in florida and see what happens!!! Honestly, the guy I bought it from bought it down from upstate new york. I do not think this bike has been ridden much in the past 3-4 years. That usually means fuel problems. What about gasoline, were these designed to work with leaded fuel???

[CB750Winger]

  I understand. It's usually a fuel issue but also make sure points, plugs, air filter, wires and timing all check good. These bikes are touchy to fine tune but once you're there, they will scream. If it's been sitting long, the best thing to do is pull the carbs apart for a good cleaning and new parts if needed. You can go to hdlparts.com for parts breakdown and prices. OEM is the best way to go for electrical and carb parts. Many aftermarket parts and "seconds" don't work.    

[woodsrider250-2]

No