The International CBX Owners Association

Hi, I've got a stock '79 CBX which, AFAIK, has never had any carb work done and I've owned for 20+ years. I've ridden in periodically over these years and it has ran well with no carb issues.

In the midst of a move to a new location without a garage, I stored the bike at a friend's house for about 2 years. Prior to hibernation, I filled the tank with non-ethanol fuel, added Stabil, ran it as bit to fill the carbs, turned off the fuel at the petcock, and drained the float bowls.

I'm reviving the bike now and with fresh fuel it starts easily and runs well. But it's pissing fuel all over engine and it flows gas whether the engine is running or not. And it's fair amount of gas, not a minor seep. It's not coming out the overflow hoses, it's coming from someplace on the carbs itself and appears to be coming from both banks. I'd think it was probably float bowl overflow, but shouldn't this overflow go to the hoses on the bottom of the carbs? If it is sticking float bowl valves, is pulling the carbs the only option?

- Mark

Welcome to the site, Mark.
Sometimes a rap on the float bowl can dislodge a stuck float.
Sounds like yours are leaking from the connectors between the carbs. The rubber o-rings deteriorate, shrink or become brittle and allow the fuel to leak.
Could also be something like a cracked overflow tube inside the bowl.
I think you have a carb rebuild in your immediate future.
Parts, info and even a rebuild service can be found on the Mike Nixon site. http://www.cbxcarbs.com/

Thanks for your suggestions. Man, I just hate the idea of pulling the carbs. I've done it on so many bikes and it just is a PITA. And as I understand it, the CBX requires tilting the engine.

At the moment, I'd just try and ID the most likely source of the leaks. I doubt it is a single point of failure as all (or nearly all) of the six carbs are leaking. So this points to something in common that happened to all of them while the bike was sitting, probably seals or o-rings drying/shrinking. In retrospect, I wish I had just left the carbs undrained - I've done this during previous periods of inactivity of a few months at a time and had zero issues.

Assuming the float valves are sticking, wouldn't they drain to the overflow hoses? Does the fact gas is coming out of somewhere in (or between) the carb bodies themselves point to something else?

- Mark

Don't be concerned about tilting the engine, I'm not a mechanic and had never worked on a bike before(other than oil changes) and that had me worried also but turned out to be a simple and straight forward process. Pulling the carbs maybe the easiest way to figure out whats leaking and where. Besides if the leak is not at the fuel hose connection then they likely have to come out for repair.

There are VERY few CBXs out there now doing well on their original carb O-rings. No matter what you did to store the bike (and you did it correctly), these 40 year-old O-rings fail. Carbs have to come off and be totally dismantled. No way around it. Get them off and send them to Mike!

Dave

Mark --- if you DIY, be certain to use Viton material orings. See Mike Nixon, Randakk, TIMS. It's the orings -- trust us all who have been there.

Thanks guys, even though you're not giving me the magic bullet (e.g., pour X in the tank and wait 17.5 hrs and everything will magically be sealed up) answer I want. These carbs are 40-yo.

When everyone says "o-rings" these are the ones sealing the short metal fuel lines that run between the carbs, right? Just replacing these seems pretty easy and I would consider just doing this as the bike runs well other than the leaks, but OTOH, it appears you have to separate the carbs to replace these o-rings and that looks tricky as heck.

Is Nixon the consensus choice for a carb overhaul? After I go to all the trouble to get the carbs off, I should probably do the whole enchilada and get a full rebuild.

- Mark

Like everyone had said, most likely the O rings but take the fuel tank off, maybe you'll be able to see better where leak is coming from

Got the carbs off. I honestly couldn't tell exactly where they are leaking from, but I'm tending towards getting a full rebuild anyway, so doesn't really matter as everything will get renewed.

Tilting the engine worked well. Nixon's "Removal Tips" really helped, especially showing the proper way to pry to get the carb bank to pop out of old rubbers. The hardest thing was probably getting the darn pull throttle cable off the bellcrank.... man it is buried up between the carbs and the slot the barrel goes in makes the job a lot tougher than it needs to be.

- Mark

There's a trick to that,

Have you decided to go with Mike's full rebuild? You won't regret it!

Dave

daves79x wrote:Have you decided to go with Mike's full rebuild? You won't regret it!

That's the plan. I'm typically a DIY-cause-someon-else-isn't-as-careful-as-I-would-be kind of guy, but Mike obviously takes a lot of pride in his work and I want to give myself the absolute best shot I never have to do the job again. The folks who take the carbs on/off multiple times to sort jetting/problems..... may hat is off to them.

- Mark

Jeff Bennetts wrote:There's a trick to that,

Cool trick. Mike's video on how to get the cables on is pretty good too.

- Mark

You will be happy after having Mike do the job. Should not require synch afterwards, either!

Larry Zimmer wrote:You will be happy after having Mike do the job. Should not require synch afterwards, either!

How do you get them spot on on all cylinders without hooking up gauges? As you know this 6 cylinder needs to be spot on to keep the clutch rattle to a minimum. I know you do the bench sych but you can only get it so close as all engines react differently with different compressions and all. I am all ears on this as I want to learn on this also.