Okayi know its a cbr forum and that what I ride, however i just bought a 82 yamaha 550 for my lady and its having some issues. We got it running and rode it around for a little while until it died from what seemed to be starvation of fuel. I brought it back to the garage and took out the airfilter, sprayed some carb cleaner into the carb horns and tired to start it, i can get it running at around 1100 rpms but i have to keep the throtle wide open to get it to stay there or else it dies again. I'm thinking the jets in the carbs could be clogged, anybody have another idea before I tear into the carbs? The bike had been sitting for about 6 months before we fired it up. Any help would be great, thanks.

 

Too many variables to be accurate, but how was it running before it quit? Is it a vacuum operated fuel petcock? Has the tank got fuel? If so, is the fuel feeding to the carbs?

If you are having to keep the throttle open, then the float bowls may be starving of fuel.

Things to check:
1. Fuel in tank?
2. Fuel getting to the petcock?
3. Fuel getting THROUGH the petcock?
4. Fuel getting through the float valves?
5. Float valves working well?
6. Any vacuum leaks?
7. Slider diaphams in good condition? No holes, cracks, etc????? (This will cause vacuum leaks as well as prevent the slides from lifting correctly.
8. All carb passeges cleaned and free of crap?
9. Jets all clean and free of crap?
10. Carbs synch'd?

 

There is new fuel in the tank, it sputtered a little bit at low rpm's but past 4k it ran great. It is a vacuum opereated petcock and I can see the fuel running through it. I just pulled the plugs and they are black, not to much crud on them though. I think the problem has got to be carb related, I'll know more tonight once I pull them apart. Thanks for the check list, I appreciate it.

 

Definately pull the carbs.

Take digital pics at the highest res you can for reference.
Take notes on pilot jets, main jets, whatever you need to take notes on
Make sure you also count the turns for the fuel air screws so you can set them back the same.
Make sure you pay REAL close attention to the float valves and make sure the little nipple on them depresses and is not stuck
Clean the crap out of hte pilot jets.

Your issues seem to be in the bottom end, and that is pilot jet related. Remember: There are three overlaying circuits in the carbs, bottom end (for idle and just off throttle. Pilot jet and a/f screw controlled.), mid range, (affected mainly by needle height), and top end. (Affected by main jet size)

 

okay, so i took out the plugs cleaned them off in with a wire wheel stuck back in and the thing runs like a champ! no sputtering, good idle, do you still think the cabrs could be bad?

 

So....I rode the bike around for about 6 miles and the sputtering started happening again and I had to try hard to keep it running. When I took of the airbox side cover, gas came dribling out and was all over inside the airbox. It seems to me like there is to much fuel being dumped into the carbs and its coming out through the airbox. Any ideas on whats going on? Also I pulled the plugs and within the 6 miles I rode they were all black again. Any help would be great!

 

Float valves are either stuck, or there is some debris keeping them open. This is why you are draining fuel and fouling the plugs. If the carbs are anything like my Katana carbs, there "could" be a couple o-rings for the fload assemblies that may be allowing fuel to get past too, but go through the float valves first.