Why won't idle come down

[96flhpi]

When I stop at a light my idle is high unless I bring it down manually with engine braking or releasing the clutch just enough to engage ever so slightly.  Since it's got points I figured the mech advance was shot but new advance, same thing, old advance with new springs no better. 

Don't think it's intake leak because I can bring it down with the clutch and once it's down it goes to the same RPM every time and is rock steady once it's there.  I had checked and replaced the seals before ordering new advance even though it didn't show any evidence of a leak. 

FWIW I've always had better luck getting a consistent idle with the silver advance springs and am using them this time.  Maybe they're crap since they were $9 for a bag of 10 instead of the $25 for 2 I saw at J&P.

Anybody know what else might cause this behavior?

[motorplex88]

I have had this happen like you are describing. For me it indeed ended up being a crack in one of the intake bands. Not sure what carb your running but mine is the old Bendix. I would take a look.

[JW113]

This is classic symptom of advance unit sticking. A crack in the intake seals is the same as the throttle being open. If it runs at high rpm, then forcing it to drop rpm by using the clutch/brake and it goes back to normal doesn't seal the leak in the intake. What you are describing is the advance weights getting stuck in the advance position. Just my thoughts, could be wrong. Usually am. LOL!

Don't know what you're using for a mechanical advance, but I can't stress enough don't go cheap. Get the Rivera, keep it lubed up, be done with it.

-JW

[motorplex88]

I'll agree with JW in the statement about a crack {leak} in the intake would remain a constant....you would think. I found in mine that not to be true. It was a fine hair line crack that I had to take the carb off and look good to find it. I would have thought I would find it with the ol shoot brake clean method. Changed the bands and problem went away. Go figure. I missed the part where you said you changed your intake seals so you most likely have that issue covered. I'll shut up now.

[96flhpi]

Thanks for replies.

That's weird Motor - I was gonna say every time I've had a leak I've had to fiddle with the idle adjust constantly so it can't be that, but I guess I can't rule it out.  It's been exactly the same before and after the seal change though.

JW I replaced a 15 year old Rivera with an American Prime unit, supposedly made by a former Rivera employee.  It's US made, cost as much as the Rivera, and looks EXACTLY the same as the Rivera other than the name on the weights.

My new thought is that maybe the can of white lithium grease I've been using as lube has gone bad.  Does that stuff have a shelf life?  I've been using the same can at least 10 years - at beginning of season I disassemble unit, clean, spray on lithium, let it set, it leaves a film behind and there's very little fling off.  When I pulled the advance last night there was a small pool of liquid grease in the bottom of the cone (usually there's so little I can clean it with a q-tip but this took a few paper towels) and the unit looked pretty dry.  I redid the unit with wheel bearing grease but won't get to test it until tonight. 

Might explain why it seems fine when I first redo it but comes back within 3-4 miles, and why it's happened with more than one advance.  I thought it may have to do with the unit heating up but maybe it's just flinging off all the lube.

[JW113]

Yes, lithium grease aka Lubriplate does go bad. Starts off fairly white, turns into what looks like hummus over time and gets thicker That's the oil oxydizing. Personally, I would not use lithium grease in a high temp application. For the advance weights and other places on the motor that need some lube, I like that high temp caliper grease.

-JW

[motorplex88]

Good idea on the caliper grease. I usually just used the grease from those little pills that comes with ignition points. Never have known what that stuff is.

[Hossamania]

I always used that grease too, way back when I changed points on my cars a million years ago. I was told it was non-conductive, and that regular grease was not recommended.

[Dogbone45ACP]

I use anti seize on advance units . What ever brand you like. Works well.

[kd]

White Lubriplate is formulated to absorb water and prevent rust spotting in stationary load bearing surfaces.  I agree that you need to use a high temp lube with stringy cling characteristics.  The kind that is hard to clean up with a dry towel because it leaves a film.

[JW113]

This is what I use. You don't want grease getting on the disk, so it tends to stay in place even with high temps. Which seems to make it work good on hot ignition parts.

[attach=0]

-JW

[96flhpi]

Installed unit with the wheel grease lube, went for a 40 min ride, everything was great for 35 mins of it and last 5mins problem returned.  Pulled the points plate and advance is plenty lubed still.  Thinking ok problem comes with engine fully warmed up, but previously I've replaced the unit on an engine that only cooled for the time it took me to do the exchange and it's been good at first and returns after 5 mins.

But now I'm back to maybe it IS a small air leak.  I did have the heads off for a valve job not long ago, and yes I re-torqued after installation, but maybe it's a small head gasket leak, or intake leak that I failed to fix first go around - and also yes the heads were clocked to the intake.  It started maybe a week after the heads were reinstalled, in fact I think it started after the final retorque.  Gonna pull the heads and start over because I'm outta ideas.  Hopefully I didn't pull an insert.

On that note, I have copper and blue teflon head gaskets on hand (I usually use James Fire-Ring).  The teflons are probably 8 years old, do they have a shelf life?  If they do I'll try the copper, but prefer the teflons just because I've never tried the copper before.

Also, FWIW, I've been using that white lithium to lube the advance for like 13 years, never had a problem.  In fact it was most likely suggested by someone here, back in the MSN days.

Thanks again for any advice.

[PoorUB]

I seriously doubt it is a head gasket. When I head gasket starts to leak they blow out fairly quick and you start hearing a chirp.

How many miles since the problem started?

[xlfan]

What kind of carb?

[96flhpi]

UB - I know I've filled up the gas 3-4 times so 400-500 miles maybe, haven't been keeping track.

XL - It's happened with two different Keihin CV's and the original butterfly so probably not the carb.  I thought carb too after it came back with the new weights.

I read that too much advance can cause this so when I set the timing after installing the advance last night I retarded the timing maybe 5 degrees just to rule it out, but that wasn't the problem.

I too doubt it's a head gasket but other than an air leak of some kind I'm all out of ideas.  The only reason I'd pull the heads and start over is because I have all the gaskets I need on hand and have been chasing this for 2 weeks - if I redid everything I could be up again over the weekend.  I also commute on this bike so don't want to be putting on a lot of miles if it's possibly a leak and do damage, although the oil temp (tank gauge) has been normal.

[guppymech]

In my experience with car engines, a vacuum leak causes rough running and a lower idle rpm.  The presence of a vacuum leak could be verified by cupping your hand over the carburetor inlet with the engine at idle, if the idle sped up and smoothed out there was a leak somewhere.  Slightly blocking the carb inlet with your hand gives a richer mixture that corrects for the vacuum leak.

What year is your engine and do the heads use o-rings or bands?  My heads use bands and I find I get a better intake manifold seal using 4 thin wormscrew clamps than either the stock or aviation style clamps.

It may be a crack that needs a full heat soak to open up enough to cause problems.  From a cold engine it takes a good ride to act up but the time you changed the advance unit on the hot engine the problem came back in 5 minutes as she cooled a little during the iggy swap.

I will say, anytime I've had a motorcycle engine idle take off like yours it's been from the advance unit, both my old Norton and current FXE.  They wouldn't do it like clockwork, just once in a while with the Norton being way worse.   Do you have a stock H-D advancer you could try?

My take on head gaskets.  I'm using Cometic .032 copper, coated with Permatex Copper Spray-a-Gasket torqued to 55 ftlbs with no leaks.  The gaskets are reusable after annealing with a propane torch and cleaning off the scale.  I'd anneal the new gaskets before you use them also.

Sorry I'm all over the place with my post but this is a odd problem you have that is difficult to troubleshoot over the internet.

Tom

[xlfan]

Have you blocked unused vacum ports on the carbs?   

[Burnout]

Put a timing light on it when it is acting up, to see if it caused by the advance not rolling back.

Any vacuum leak would cause driveability issues.

[JW113]

You mentioned two CVs, where/how do you have the enrichener cable mounted? Is there any chance the enrichener is opening slightly, which will also cause a high idle. Doesn't explain the stock butterfly carb doing it also, but something to check I suppose.

-JW

[kd]

If it was an intake issue I doubt after forcing the idle down with the clutch in gear it would stay there as you say.  I suggest you go back into the advance unit and blueprint it.  Just because you have new springs, doesn't mean they are not screwing up by not pulling the weights back at lower RPM. There may be a bent post or the weight(s) may be dragging or hooking on something on return. Did the plate get warped when installed by the way it was set in place?

After 3 carbs it probably isn't that.  It could be a manifold problem but as I said it doesn't pick back up with the clutch in. Spraying the manifold seals will test them anyway. This sounds to me like the advance plate is hanging up for some reason.

I would try to polish all contact points and check for damage that may be causing a tight spot on return.  If you shut it off when the idle is high does it restart at a high idle or start out low again? Can you run it with the cover off so you can see if it returns?

[Racepres]

Just for "Potty mouth"s and Grins... replace the condenser with a known good one... I have had them go Flakey... especially "new" ones...
Generally however... bad condensers either simply won't run... or Fire up fine, but will Not pick up RPM...

[JW113]

This is a bit extreme, but if you suspect an intake leak, here is what we do with old Indians to locate intake leaks, which are kind of common with their funky manifold to head spigot compression joints. Get a 1-7/8 or 2" rubber stopper from ACE or True Value or where ever, drill a hole in the middle. Roll the motor over until both intake valves are closed. Pull the carb, force the stopper into the intake manifold hole, and use a compressed air blow off gun to blow air into the manifold. KEEP THE AIR PRESSURE LOW, like 5-10 psi. Then use soapy water sprayed around the intake manifold joints, head gaskets, etc, and look for bubbles. We call that "the bubble test". Clever name, eh?

-JW

[david lee]

This is a bit extreme, but if you suspect an intake leak, here is what we do with old Indians to locate intake leaks, which are kind of common with their funky manifold to head spigot compression joints. Get a 1-7/8 or 2" rubber stopper from ACE or True Value or where ever, drill a hole in the middle. Roll the motor over until both intake valves are closed. Pull the carb, force the stopper into the intake manifold hole, and use a compressed air blow off gun to blow air into the manifold. KEEP THE AIR PRESSURE LOW, like 5-10 psi. Then use soapy water sprayed around the intake manifold joints, head gaskets, etc, and look for bubbles. We call that "the bubble test". Clever name, eh?

-JW

ive done the soapy thing before but not your one.makes complete sense

[JW113]

Another less conclusive way, but can work as well, is to take a spark plug out, crank the motor over to get that on the intake stroke (valve open), leave the carb on, and use the compressed air into the spark plug hole. You'll pressurize the intake manifold and carb a little. The throttle plate won't hold back the air, but with higher pressure (60psi or so) it will be enough to expose any leaks and make bubbles.

-JW

[96flhpi]

Thanks all for replies.  I'll tell you latest in the saga first then answer your ?'s after.

After work decided to see if it's still "everything perfect until engine fully heated."  It is.  However tonight, with butterfly carb, it coughed enough to stall the bike at start up (usually coughs a few times when dead cold but not enough to stall bike), ran perfectly once warmed up enough to take throttle - no coughs, no hiccups - for around 1/2 hour.  Then the high idle returned and started to get an occasional hiccup if I gunned it off coasting, then coughs at stops, then coughs at stops that'd stall bike.  Easy, now it's an obvious intake leak, right?

Problem is, that is what this carb's M.O. is - every few years I get both nostalgic and forgetful and put it back on and it runs perfectly for a week, then needs constant A/F adjustments, then by the end of the second week it's coughing so much I replace it with the CV.

Since I'm putting the CV back anyway I pulled the intake to inspect the rings and although they're not torn or split I did find that while one had a clearly defined witness mark around the entire circumference where it filled the intake/head gap, the other had the defined mark around 2/3 or so then the mark blurred to where I was questioning whether I could see it or not.  I'm seriously hoping Motorplex hit on it early on.  I have been keeping the clamps a little looser since I overtightened them and caused a leak a few years ago but made them tighter with new rings.

Guppy - it's got O-ring style intake.  When you say vacuum leak do you mean an intake/gasket leak?  If not there's no vacuum system to leak.  And no, don't have an OEM advance to experiment with.

XL - both CV's VOES ports gunked over with silicone and capped with a little plastic cap.  Doesn't mean they can't have opened but the butterfly has no VOES port.

Burnout - not sure if that would help.  Wouldn't the timing show advanced whether the weights were being held open from binding or the usual centrifigul force? 

JW - CV choke mounted to engine mount between heads, butterfly choke on dash, checked both early on in the process.  Great advice on the intake leak checker.  I've seen machinists make them out of aluminum and an old inner tube but I'm not a machinist.  Your's only requires the tools I already have.

KD - this has happened with three different units - old Rivera, brand new American Prime, and one cobbled together from spare parts of crappy Chinese ones.  Tried 2 sets of springs on the Rivera and 3 on the American Prime.  Oddly enough the cobbled together one lasted the longest before the problem came back.  Restarts at normal idle until I give it throttle then hangs up immediately.  Can't see the weights running the points plate blocks them.

Race - it's my also experience that condensers typically either work fine or they don't at all.  But unless these new intake seals are the answer I'll give it a try.

Thanks again everyone, rainy tomorrow so back at it Saturday.