Re: Carb issues I think! (1981 CB750K)

Posted by kramit on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Carb-issues-I-think-1981-CB750K-tp2921415p3191114.html

I have a 1981 CB750C. and was wondering if you got your bike to run any better. My bike has the exact carbs Keihin 42A . On top of these carbs there is a automatic petcock valve looks like a octopus, which only allows gas to enter carbs when starting. This part has been known to starve carbs for gas. If you have this on your carbs throw it out, and run the gas line, and put in fuel filter directly to the carb gas inlet tube. They put this on so you would not have to turn your gas petcock off manually evertime you park the bike. There is a small black hose that will need to plug that comes off the number 2 carb, I cut the tube about 1 and 1/2 inch plug with bolt or screws. This may not solve your problem, but this part
on all web sites will eliminate this to narrow down carb issues. These carbs I had to take apart a number of times, and they can look clean, but there are a lot of very small passages, and they need to be cleaned.
The pilot screws have tabs to keep from adjustment just cut small tab off with drimel cutting wheel, I have mine set at 2 and a 1/2 turns out I run stock pipes with pod filters so this can be set diferent if running header exhaust. It sound like 1 or more float bowls are running out of gas, runs great then bike needs more gas. other causes can be your accelerator pump as others have mentioned. These carbs were the sync-screws ever removed becase this would throw off carb being in sync. Also check plug wires,and put in a new set of plugs they are not expensive. If you have rubber hoses on bottom of carb, get a container, and make sure each bowl has gas comming through open 1 at a time, and watch flow.

Good Luck
Kramit