Topic: Hanging idle....I'm done

[Scott S]

 That's something else to take a look at. I know I usually ORDER the correct plugs and caps, but I'll verify what they actually sent me. I have heard of that being an issue for other people.

[Scott S]

When you say the idle fixes itself by slipping the clutch...........it usually indicates a vacuum issue in the slide/butter-fly area on one or more of the carbs........it could be dirt.......or physical damage to a component.........or a slightly warped carb-body.

 I guess so, but I handle these carbs on the bench myself,  and the throttle operates properly when not running.
 Would I be "lucky" enough to get three sets of carbs like that?

[Scott S]

 Checked the mixture screws and they are the type with the hole. Unfortunately, that's all I have in my spares, too. No solid ones. Set them all at 1 turn out just now.

 Checked again for vacuum leaks all around the carbs, intake and manifolds.....nothing. Checked exhaust pipes for leaks....nothing.

 Checked throttle operation cold and hot....works fine and snaps back.

 Plugs are NGK D7EA. Caps are XD05F and VD05F. The VD05F caps are the weird kind that use the cap on the end of the plug and I don't like the way they fit. I'll see if I can get a replacement set of those, BUT.... the other bikes had the other style that fit snug and they still had this issue, too.

 It actually hung up on me on the return to the garage and rolling forward on the throttle does nothing. Neither does a slight rev. It was in neutral at the time and revving to over 2K. I have to hit the kill switch momentarily and it will drop back down. Otherwise, I'm crunching gears to get it into gear.
 If I downshift or use engine braking, I can make it manageable. I can feel/hear it doing it a little bit, though.

 Dug out the points plate and cam (Good TEC parts). I will pull the advance and swap out the ignition soon.

[dave500]

you can solder the screws with holes solid,look closely at my photo and youll notice,the drilled screws you can only enrichen so much,they pass air even when fully closed,youll get more control with solid screws.

[Scott S]

[maxheadflow]

You need to put a set of vacuum gauges on the motor. It sound like a couple of the slides are hanging up.  Check the linkage on the slides.  Carbs don't sound too well synced either.   

[Scott S]

  They are vacuum synced.  But I'll do it again and take a video to prove it.

[maxheadflow]

When the throttle hangs look at the vacuum.

[Scott S]

 Not trying to be thick, but if the throttle hangs and revs are up, vacuum will be high. What will that tell me? Seriously....educate me.

[maxheadflow]

Not trying to be thick, but if the throttle hangs and revs are up, vacuum will be high. What will that tell me? Seriously....educate me.

I would think that you have a slide or 2 hanging. If that's the case the carbs will go out of sync.

[Scott S]

 Ah, gotcha..... I would see it on the offending slide(s).
 But.....wait.... they're all on a common linkage. One can't hang and the other three drop....right?


 And is this the third set in a row?

[david 750f]

Scott, try disconnecting the throttle cables from the carbs. Manually move the rpm at the carbs and see if you can replicate the hanging idle. At least you can eliminate the cables and/or the carbs..

[maxheadflow]

Ah, gotcha..... I would see it on the offending slide(s).
 But.....wait.... they're all on a common linkage. One can't hang and the other three drop....right?


 And is this the third set in a row?

If the linkage was new and in perfect condition, they should. 

Not sure which linkage your carbs have but some utilize springs to keep slide link in tension with an adjuster.  Some use riveted links.  Rivets can come loose, springs can become weak.  Generally pulling up you have slack taken out. Return not so much.

[HondaMan]

Scott:
In the midst of this stuff...what grade of gas is in it? Is it Regular, or is it some higher octane? It should be Regular with today's fuels, as they burn much slower than the fuels of old. I run Regular for everything except Interstate riding, anymore. The slower-burning fuels leave wetted surfaces in the 500/550 (and less so in the 350f/400f, but enough) intake, especially with any spitback issues, leading directly to over-fueled idle situations. The waste-spark cycle, if the timing advances too far at lower engine speeds, makes this real bad in the 500/550 in particular. Spitback wets the intake tract, directly causing hanging idle and sluggish performance below about 5k RPM.

In all of these engines, I have found that the starting angle (timing marks) must be on the "F" for each side below 1000 RPM. If it is not, the idle will hang on most of them, regardless of weak/strong spring issues for the advancers. When electronic triggers then get fitted, whatever timing advance you get at 3500+ RPM is what you get: there isn't much that can be done about that because of the way they work. If it is more than the normal full advance there will be a flat spot around 4000 RPM while the carbs and cam argue with each other for a bit, above that it straightens out again, much like a fixed-advance racing engine does. If it doesn't advance all the way above 3500 RPM then the gap of the electronic triggers is the issue, because the magnet(s) take some time to trigger those sensors. On those electronic units where the timing cannot be individually adjusted for the 1-4 and 2-3 sides, trouble is almost guaranteed. The old Marktek was famous for this latter feature, as were the older (but sadly more reliable?) Dyna S devices.

[Scott S]

 I'm using 87 octane ethanol free gas.
 On the Pamco's. I was able to increase the plug gap and advance the idle a tad, maybe the width of the hash mark.

 The last two bikes have been gapped to spec and set on the mark.
 When I put the points back on today, I set it exactly on the mark.

[Maraakate]

Could it possibly be something really silly like a hairline crack in the airbox?  Is the hose for the plenum intact?  If yes, is the little foam filter in it still intact and in good shape?

[dave500]

if the idle hangs and you can stall it down with load,then blip the throttle and it hangs again its lean man,itll be super rare to have a sticky slide,the way the linkage works on the 500/550s itll get forced down if it aint bent so bad youd never get it in its bore,plug some airscrews and humour me.

[Deltarider]

if the idle hangs and you can stall it down with load,then blip the throttle and it hangs again its lean man...

I agree

plug some airscrews and humour me.

All CB500s had the cross drilled type air screws. The CB550Fs had the solid ones. Personally I never felt the need to plug the airscrews. Mine (a CB500) work fine.

[Scott S]

 Alright, I'll go along with the possibility that it's a lean condition. I do have some stock paper filters I can try; one EMGO and one genuine Honda. My silver bike (that had a ported head, oversize valves, CB650 cam, open exhaust, etc) did't like the paper filters and ran better with the UNI. Easy enough to swap out a filter to "choke" it a bit and see if it changes anything.

 While this is CB550 number 8 or 9 for me, I don't understand why, after so many bikes, a proven combo would all of a sudden start being lean.

 IF the test proves a lean condition, would you start with bigger pilot jets? Raise the needle?

 I did try turning the mixture screws in and out and they have little effect, but that's also been common on ALL of the 500/550's that I've owned.

[minimo]

Over time, foam-type filters can disintegrate and the tiny cells can clog up the carb passages. I had installed some foam cheapies (UNI knock-offs) on a 550 and found bits of foam blocking passages inside the carbs. I was also getting similar hanging issues. Pull the carbs, take it all apart, and clean them throughly, blowing compressed air through and around all of the passages. And then after that, clean them again.

Oh, and this chart has always helped:



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[MauiK3]

If all else fails, perhaps try to set up a fixture to seal off the intake and exhaust tracks so you can individually fill them with fluid to see if you have an unseen leak somewhere in the casting.
Or perhaps find a way to pressurize the tracks to see if you hear/see air or water leaking.
A bit out there but if you've run out of ideas............

[Scott S]

 And again.... would I be lucky enough to have an oddball issue like that on two bikes?

[grcamna2]

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[grcamna2]

Scott, try disconnecting the throttle cables from the carbs. Manually move the rpm at the carbs and see if you can replicate the hanging idle. At least you can eliminate the cables and/or the carbs..

Scott,Have you tried allowing more free-play in your return and pull throttle cables ?

[Scott S]

 Only running a pull cable. Free play is set up just like all my SOHC4's.