Topic: Erratic throttle/idle on 77 cb550f

[77_550ss]

If this has been covered, I appoligise but I was unable to find a like post.

That being said, here is my problem.  The bike will sometimes idle ok.  sometimes it will idle crazy fast & yet other times it won't even idle.  It will foul plugs sometimes but do fine the next.  I can snap the throttle quickly  & have great response one time then it will not return to close the very next time.  It will scream down the road then without warning, it will struggle to stay alive.  I am becoming very irritated at this.  I have an idea that it has something to do with the throttle, carbs  and/or battery, but don't know for sure.  I replaced the plugs today with new NGK's, gapped at .7mm. Could there be a loose wire connection somewhere? The battery is about 18 months or so old. Could this be the problem? I am sure it is something stupid I am overlooking or just plain don't know what I am looking for.

All help is appreciated very much.

[MrZxp]

Could be any number of things.

I'm thinking, to eliminate all causes, and to know you've got everything right, you ought to start with the tank. When was the last time you cleaned your tank out? While you are about it, unscrew the petcock and check the condition of that. Look for debris in the mesh filter etc. When reinstalling, an in line fuel filter would be a good idea.

Have you ever had your carbs apart? A thorough cleaning will allow you to eliminate that cause. How about replacing the float valves? I guess what I'm suggesting is a complete overhaul of your carbs will probably be beneficial. Also check that the carb rubbers between the engine and the airbox are not letting extraneous air in.

What about the air filter? In good condition? Needs replacing?

Most of your problem sounds like fuel delivery inadequacies to me.

Cheers, Phil

[speedy gonzalais]

im guessing that the foul plugs points to a mixture problem as mentioned above if air is leaking in some where that would make it impossible to get the idle right if the float valves where shot then fuel would pour out the over flow thats if they aint blocked.
and yes the best way is to take the carbs off and check the jets mainly the idle jets i dont think your battery is the problem if it was too flat the bike wouldnt run at all
and does the bike back fire

[TwoTired]

HAs it had a complete and thorough tune up in the last 3000 miles?

Is the air filter over 1 year old?

Does the bike have stock air filter and exhaust?

When were the carbs last vacuum synched?