Big Carb Problem

RMBillings · Post by **RMBillings** » Sun Feb 11, 2007 4:31 pm

I am in the last steps of my 1979 CBX and I am having Carb problems. I had the carbs cleaned and new jet kit put in but the motorcycle is running really rough and will not idle below 1500 rpm. When I was working with the carbs today the air cut off valve joint in between two of the carbs pulled out. The rubber had dry rotted and cracked appart. Does anyone have an idea on what I should do here? I there anyone out there that works on these carbs? I really don't want to break the rack myself.

Any help or guidance would be great.

Thank you.

Chris · Post by **Chris** » Sun Feb 11, 2007 8:28 pm

Rob,

The symptoms that you describe can be caused by a variety of things.

Since the carbs were just rebuilt and if we assume that they are in good working condition.............

If they bike runs rough and won't idle below 1500, you may have fouled a plug. I would suggest pulling your plugs and looking at them. While the bike is running you can spray a mist of water on your head pipes, problems can often times be traced to a particular cylinder in this manner.

Another potential issue may be a big vacuum leak. Possibly at the carb mounting collars.

Did the bike run good before the carb work?

RMBillings · Post by **RMBillings** » Sun Feb 11, 2007 9:10 pm

I checked as it was running and it seems that cylinder 1 and 3 are not running all the time. I took about all the plugs but the problems is still happening. I checked and I have spartk to all the cylinders.

Any ideas?

Chris · Post by **Chris** » Sun Feb 11, 2007 9:47 pm

How did you figure out that 1 and 3 weren't running properly?

Sometimes you can move/swap parts to help eliminate variables and narrow focus on your core issue.

1 and 3 don't share a coil but you may want to swap spark plug wires/boots and see if your problem moves. Same thing with your plugs.

Also, if you haven't already done it, it would pay to snug down your carb collar screws.

If the problem isn't traced to ignition, then you would next need to take a close look at your carbs.

Please keep us informed what you find.

cbxtacy · Post by **cbxtacy** » Sun Feb 11, 2007 9:50 pm

do 1 and 3 run okay when you give it throttle but they're just not idling?

Jeff Bennetts · Post by **Jeff Bennetts** » Mon Feb 12, 2007 11:26 am

With a good set of plugs in the bike, let the bike idle and check the temp of all the header pipes, if you have 1 or more cold cylinders a couple things could be wrong.

1. bad coil if the cold plugs are using the same coil.

2. clogged idle circuit or circuits, most likely the problem.

The hose that pulled off is the breather hose, 1 for each bank of 3 carbs, don't sweat it but the tees are available from Honda or CBXman.

rbarber · Post by **rbarber** » Thu Feb 15, 2007 8:20 am

Jeff Bennetts wrote:The hose that pulled off is the breather hose, 1 for each bank of 3 carbs, don't sweat it but the tees are available from Honda or CBXman.

Is it a breather or an overflow?

EMS · Post by **EMS** » Sat Feb 17, 2007 1:28 pm

Most likely one of the "overflow" tubes between carbs 2 and 3 or 4 and 5.
They have little "tees" on the end that crack. I have been running my 79 without them for years. I don't want to break the carbs apart. Although I faintly remember that someone (maybe Nick -cbx4evr) did install new ones by squeezing them on to the tube ends without disassembling the rack.

Chris · Post by **Chris** » Sat Feb 17, 2007 3:33 pm

EMS wrote:Most likely one of the "overflow" tubes between carbs 2 and 3 or 4 and 5.
They have little "tees" on the end that crack. I have been running my 79 without them for years. I don't want to break the carbs apart. Although I faintly remember that someone (maybe Nick -cbx4evr) did install new ones by squeezing them on to the tube ends without disassembling the rack.

That was me on the vent tubes. They can be "pushed" on with a blunt tool and some lube. I'm getting ready to do it again.

EMS · Post by **EMS** » Sun Feb 18, 2007 11:55 am

Chris

We are talking about the "tees" that go on the short brass tubes sticking out between the carbs

You need to send me this instruction somehow.

I would really like to try it, but I could not find the how-to anymore

I thought it was in a place where I am considered a persona-non-grata and did not want to venture there.

Jeff Bennetts · Post by **Jeff Bennetts** » Sun Feb 18, 2007 2:46 pm

EMS wrote:Most likely one of the "overflow" tubes between carbs 2 and 3 or 4 and 5.
They have little "tees" on the end that crack. I have been running my 79 without them for years. I don't want to break the carbs apart. Although I faintly remember that someone (maybe Nick -cbx4evr) did install new ones by squeezing them on to the tube ends without disassembling the rack.

EMS, the top hoses are vent tubes, they equalize the carbs to the outside atmosphereic pressure, the overflow tubes are on the bottom of the carbs.

The hoses on the top tubes keep debries out.

EMS · Post by **EMS** » Sun Feb 18, 2007 4:06 pm

Jeff Bennetts wrote:EMS, the top hoses are vent tubes, they equalize the carbs to the outside atmosphereic pressure, the overflow tubes are on the bottom of the carbs.

The hoses on the top tubes keep debries out.

Thanks, JB, for pointing that out. I wasn't considering that the overflow and drain tubes are the same. I was thinking low is drain, up is overflow. If I just would have remembered that the standpipe in the float bowl connects to the same outlet as the drain screw.