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

[Scott S]

  I can't get away from hanging idle issues lately and it really pisses me off.
 The last three 550's have had the same problem.

  No intake leaks. Jetting is good. Timing is good. Trim advance springs. Clean and lube mechanism.  Adjust mixture screws. And on and on and on.
 And I don't think it's carb related because if I slip the clutch it will stop.
 Carbs are COMPLETELY disassembled, ultrasonically cleaned and rebuilt. Stock jets, bench and then vacuum sync'ed.  Timing set with a strobe light. Stock air box. No vacuum leaks. New O-rings on the manifolds. Complete 3,000 mile tune up.

 You name it, I've done it.

  This has been an issue when trying to sell a bike. I'm out of ideas here and don't really even want to work on it anymore. What should I try? Trim another loop off the advance spring(s)?

 Anyone wanna buy a bike, as-is, and take a shot at it yourself?

[Kevnz]

Hi Scott,
I'm really sorry this bike has got to you so badly. My 500 was giving me serious grief earlier in the year, but I eventually sorted it, the next ride I went on was one of the most memorable of my life and all was forgiven. So hang in there. On a practical note, are you able to beg, borrow or steal another set of carbs complete as a means of eliminating carburation as the issue? At this stage step by step substitution of various components might be a good strategy. Good luck!

[Scott S]

 If it's the carbs, it's been three different sets.

[seanbarney41]

I would try bumpin' up the pilot jet number one size

[robvangulik]

I'd love to get my hands on it, but that isn't practically possible.
In any of those three sets, did you ever change the size of the idle jets? Does anything change in the hanging condition when you turn the idle mixture screws in or out?
Hanging idle is often a lean condition, did you ever intentionally try to make the bike run rich at low revs? By lifting the needle, enlarging the mainjet ....usually it is better to start on the rich side and slowly lean out than the other way round!

[Scott S]

 These have all been stock carbs/intake/jets/air box set ups. Combos that always used to work for me.

 When the bike is in gear and it does it, I can slip the clutch and make it stop. That's why I suspected the advance mechanism and cleaned it and trimmed the springs. If it's a true lean condition, why would engine braking or slipping the clutch stop it?

[robvangulik]

The advance mech is so easy to check (and make changes to) I thought you had done that along time ago...
Take the ignition cover off and turn the advance cam with 2 fingers, you'll feel right away if it works okay or hangs up.....

[seanbarney41]

These have all been stock carbs/intake/jets/air box set ups. Combos that always used to work for me.

 When the bike is in gear and it does it, I can slip the clutch and make it stop. That's why I suspected the advance mechanism and cleaned it and trimmed the springs. If it's a true lean condition, why would engine braking or slipping the clutch stop it?

I don't know either but I have never had a sticky or stuck advance mechanism cause a hanging idle either although it certainly makes sense.  I have only ever had vacuum leaks, lean jetting, or extremely out of balance carbs cause hanging idle.

[Scott S]

 I have checked the advance. Cleaned, trimmed both springs one coil, snaps back nicely.  Electronic ignition,  time with a strobe gun. Dead on the marks at full advance.

 Carbs were bench synced and then checked with vacuum gauges.

[robvangulik]

Then the advance is above suspicion, it seems, so it has to be carbs.....
Time to take drastic measures, like I said, try to make it run rich, that should at least prohibit hanging high revs, and than slowly lean it out until it runs right.

[seanbarney41]

I know.  You said all that already.  So that leaves lean jetting...

Scott, everyone here knows you are no newby to these and I certainly have respect for all the successful projects you have cranked out over the years.  But that just makes us all the more eager to help when you got a stickler.

...sure everything is stock and common knowledge says that engine will want stock jets but this one is telling you it wants a little more

[bryanj]

Many years ago i had a small honda that wouldnt idle right and compression was low

[dave500]

have you got solid aircrews or drilled ones?try solid ones,if you have spares you can solder them up easy,youll be able to enrichen the idle more then.

[Kevnz]

I can sure understand your frustration. I know it's a long shot, but what about standard ignition? I realize you have tested with a light and showing all good, but maybe something odd going on with electronics. Even more left field, what about a cracked head or manifold? You've no doubt checked for air leaks around the manifold , but what if there's a leak further upstream? Just a thought.

[Kevnz]

No over-exhuberant porting done on the head? Maybe gone through the port wall or weakened it enough to crack. Would then open up more when warm. Head seems to be the only thing you haven't really investigated.

[minimo]

Have you checked for leaks around the carb boots and manifold? Mist some carb cleaner around there and see if that affects idle.


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[Deltarider]

Throttle cables are routed correctly? Experiment by closing (fully) and opening one individual airscrew at the time and see if that changes RPM. The one that doesn't change RPM has a suspect idle circuit. I'm with Rob to start rich. I know Amercan Honda suggests to have airscrews two turns out. The rest of the world has one turn out. What happens with a partially closed choke (or partly covered airfilter case for that matter)? Your EI does not happen to be a programmable type, does it?

[Kevnz]

What about disconnecting plug leads one at a time when issue is present. That may indicate if it is a particular cylinder that is at fault.

[Scott S]

 To answer a few of the questions:

 - Air screws. I'll check to see which ones are in there and what kind of spares I have.

 - This bike was initially started on a standard ignition, then swapped to Tytronic. I've had it happen on three bikes now; one with Pamco and two with Tytronic. BUT....I was able to clear up 95% of it on the Pamco equipped bike by trimming the springs. Maybe I WILL try putting the points back in and see what happens.

 - Head and manifold are good. Last two heads/cams/porting have been stock, and I even did a head swap on the current bike. Valves cleaned, lapped, new valve stem seals, head gasket, O-rings, pucks, etc., etc.

 - I've checked for leaks around the carbs, both ends of the manifolds, etc. New O-rings where manifolds meet the head.

 - Throttle cable routed correctly. Snaps back cleanly. No excessive free play. Genuine Honda cable.

 - Mixture screws: I've tried everything from 1.5 turns out to .5 turns. They're currently at 1 turn out. Changing them in sets of four will effect idle speed. I can try each individual carb.

 

[Kevnz]

Certainly running out of options here. You've certainly covered all the obvious culprits. Maybe points ignition is the last choice, but seems unlikely. At least you have a few good minds assisting. Best of luck.

[pjlogue]

Throttle cables are routed correctly? Experiment by closing (fully) and opening one individual airscrew at the time and see if that changes RPM. The one that doesn't change RPM has a suspect idle circuit. I'm with Rob to start rich. I know Amercan Honda suggests to have airscrews two turns out. The rest of the world has one turn out. What happens with a partially closed choke (or partly covered airfilter case for that matter)? Your EI does not happen to be a programmable type, does it?

I would check out what Deltarider said and add to be sure you have enough free play in the cables.  Slight  binding can cause an idle hang.  I had this on my 750 when I tried to remove all "slop" from the cables.

-P.

[Nurse Julie]

Fit the standard points back on.

[Scott S]

Fit the standard points back on.

 That's the plan for the weekend. I can at least eliminate the Tytronics from the equation if it still hangs.

[Old Scrambler]

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.

[Nurse Julie]

Fit the standard points back on.

 That's the plan for the weekend. I can at least eliminate the Tytronics from the equation if it still hangs.

A hanging idle is a pain in the arse. I had the same issue with one of my SOHC/4's a few years back, I checked everything, carbs on and off, stripped, bench synced etc goodness knows how many times / rubber boots checked again and again, points checked etc and it was still happening. As a last resort, I  checked the spark plugs, I had inadvertently fitted resisted spark plugs with my resisted plug caps. I fitted new D7EA's, non resisted, and the hanging idle settled instantly and it never came back. Bloody strange.