Author Topic: Idle Issue Tracked Down (Read 3681 times)

550Resto · « **on:** May 06, 2018, 01:34:22 PM »

Hello all, I am a proud owner of a 78 CB550 that I've been having some slight issue with. I've got a slightly hanging/high idle that I can't seem to fix. I've got delkevic 4 into 1 exhaust with stock slows and 100 mains. I've got new carb to manifold boots on her with new clamps. It also has a stock airbox setup with stock hardware holding it to the airbox plenum. I have been able to find that when I lift up on the right side of the carb bank for 3 and 4 the idle drops to where it should be. I'm not sure if I should try to get new carb boots and clamps or what. This has been an ongoing issue for me and I have removed and reinstalled the carbs and tightened clamps to no avail. Any ideas or help is greatly appreciated as we are out of the "CNY Winter" and weather is starting to get nicer.

550Resto · « **Reply #1 on:** May 06, 2018, 02:08:59 PM »

I purchased oem repros for clamps and the boots are NOS I believe. I've inspected them the few times ice had the carbs off and see no tears or rips. Could the carbs be sagging on the right side causing a leak or is this unlikely? Like I mentioned I can lift up underneath the bowls on the right side and the idle comes down to normal.

BobR · « **Reply #2 on:** May 06, 2018, 02:33:34 PM »

Are the intake manifolds tight? Are the orings good? Bob

550Resto · « **Reply #3 on:** May 06, 2018, 02:41:57 PM »

Manifolds are tight and orings are new.

BobR · « **Reply #4 on:** May 06, 2018, 03:02:08 PM »

Hmmm...sounds like bases are covered for intake leaks. Could try something to spray around the intake boots and manifolds while its running... Stupid question- by lifting up on the carbs are you maybe affecting the throttle linkage? In other words is the linkage is resting on the stop to begin with? Just grasping at straws...Bob

550Resto · « **Reply #5 on:** May 06, 2018, 03:05:23 PM »

Hmmm I did change out the cables with n ee, but couldn't get the top cable on. It was like it was too short, but it should work. I'll attempt to get a picture so I can better explain.

550Resto · « **Reply #6 on:** May 06, 2018, 03:14:46 PM »

The top of the cable seems too short and I'm not able to get the end into the throttle holder.

550Resto · « **Reply #7 on:** May 06, 2018, 04:51:58 PM »

Looking at the boots that I bought that go from the carbs to manifolds, they look to be repros. I see that the repros are .5mm larger than what the stock OEM boots are. This goes for the Side A and B as well as outer diameter. The overall length in .3mm longer. Would anyone think this could lead to an air leak even though the diameters are a negligible size difference?

Spanner 1 · « **Reply #8 on:** May 08, 2018, 09:25:51 PM »

If the carb bank 'droops' on the right side ( 3 and 4 ) it may be that the carbs are not all the way into the boots. I have previously had to use a 2x4 to lever the carbs in to the boots all the way. It must be taking air if the idle improves when you lift the carb bank. Check that !

550Resto · « **Reply #9 on:** May 12, 2018, 10:33:15 AM »

I am getting to my wits end with this bike. I changed out the carb to manifold boots with genuine boots. The reproduction ones were slightly longer. Everything was put back together and I find that after warm up she still hangs idle wise when I blip the throttle. I haven't checked to see if there is a leak, but I can lift up on the carb bank on the right side when sitting on the bike and the idle comes down to where it should be. Not sure where to go at this point. I'll check for air leaks on that side, using WD-40 should do the trick correct?

BobR · « **Reply #10 on:** May 12, 2018, 10:43:08 AM »

Quote from: 550Resto on May 12, 2018, 10:33:15 AM

I am getting to my wits end with this bike. I changed out the carb to manifold boots with genuine boots. The reproduction ones were slightly longer. Everything was put back together and I find that after warm up she still hangs idle wise when I blip the throttle. I haven't checked to see if there is a leak, but I can lift up on the carb bank on the right side when sitting on the bike and the idle comes down to where it should be. Not sure where to go at this point. I'll check for air leaks on that side, using WD-40 should do the trick correct?

I have read WD40 is a safer alternative to something more volatile. Have you confirmed (I imagine you have but gotta ask) the idle screw is resting on its stop- that the cable isn't ever so slightly pulling on it? If its not a leak its mechanical, you will find it. Bob

550Resto · « **Reply #11 on:** May 12, 2018, 11:03:49 AM »

Would adjusting the IMS screws effect the idle? I've got them at 1 and a half turns out, but read another thread where that helped someone trying to hunt down a high idle?

johans · « **Reply #12 on:** May 12, 2018, 11:12:36 AM »

i would take a hard look at the cable(s) again ( proper part, routing ect.. ) only because when you physically move the carbs it brings the idle down.

BobR · « **Reply #13 on:** May 12, 2018, 11:36:29 AM »

Quote from: 550Resto on May 12, 2018, 11:03:49 AM

Would adjusting the IMS screws effect the idle? I've got them at 1 and a half turns out, but read another thread where that helped someone trying to hunt down a high idle?

You can play with them and find out but it doesn't change the fact that if you physically move the carbs the idle changes. Either the linkage is being affected or a vacuum leak is being sealed. You need to eliminate suspects. Perhaps the WD40 will either find or eliminate a vacuum leak as one. That said, the fact that it hangs after blipping the throttle and can be corrected by lifting up on the carbs makes me suspect a simple mechanical issue as well -cable adjustment, linkage etc. Have you tried physically pushing back on the linkage after it hangs? Bob

550Resto · « **Reply #14 on:** May 13, 2018, 05:26:43 AM »

Does this boot look to be on correctly? It was tight fitting on both manifold and carb sides. Want to make sure these are not on backwards. The boot not on the carbs is the way I have them on the carbs.

Deltarider · « **Reply #15 on:** May 13, 2018, 05:39:28 AM »

* 20180513_082323-1512x2016.jpg (446.98 kB
IIRC the left side (with that extra rim) needs to face the engine side.

550Resto · « **Reply #16 on:** May 13, 2018, 09:16:16 AM »

I've checked for vacuum leaks and found none. I have upped the IMS and brought it out 2 and a half turns from closed with little help to the idle and causing a too rich as heard by popping during revving. Is there an adjustment with the throttle cables that can be done? I notice when I push the throttle closed the idle settles down to where it should be. Cables are motion pro and are not binding and the throttle closed as it should.

Deltarider · « **Reply #17 on:** May 13, 2018, 09:36:55 AM »

Quote from: 550Resto on May 13, 2018, 09:16:16 AM

Cables are motion pro...

Then... are you sure you've got the right ones? Do you have US handlebars or Euro?

550Resto · « **Reply #18 on:** May 13, 2018, 10:07:02 AM »

The cable lengths are the same as the ones I pulled off the bike. It's a Canadian bike with what look to be normal handlebars? Not sure what came on them stock.

BobR · « **Reply #19 on:** May 13, 2018, 11:56:58 AM »

Quote from: 550Resto on May 06, 2018, 03:14:46 PM

The top of the cable seems too short and I'm not able to get the end into the throttle holder.

You aren't getting the slack you need with the cable not properly seated. Either its too short or its routed improperly. Maybe you can reroute it- you don't need much. Bob

550Resto · « **Reply #20 on:** May 13, 2018, 01:05:03 PM »

Is there cable adjustment at the throttle grip for the cables? Also I didn't see the adjustment in the manual.

Deltarider · « **Reply #21 on:** May 13, 2018, 01:34:27 PM »

Quote

Also I didn't see the adjustment in the manual.

If you mean the Owner's manual have a look in p72-74 in: http://www.honda4fun.com/pdf_libretti/500/CB500_550/CB500_550_06.pdf

BobR · « **Reply #22 on:** May 13, 2018, 01:45:43 PM »

Quote from: 550Resto on May 13, 2018, 01:05:03 PM

Is there cable adjustment at the throttle grip for the cables? Also I didn't see the adjustment in the manual.

My 750 has adjustments on both ends of the cable- I imagine the 550 does too (if thats what you mean). You should be able to adjust a small amount of slack into the upper (pull) cable by using the two adjusters. Same with the lower push cable. If you cant something is wrong. Wrong cable, or very heavy bends in the routing if its close (to having slack) perhaps.... At any rate you should have about 1/8" free play in the throttle when its adjusted properly. Bob

przjohn · « **Reply #23 on:** May 13, 2018, 03:48:36 PM »

Maybe I'm not following the thread well.
What problem do you have:

A. When the throttle is blipped the bike idles high but after a little while comes down to the normal idle.

B. The bike idles high all the time.

Also, have you synched the carbs?

550Resto · « **Reply #24 on:** May 13, 2018, 04:47:04 PM »

After initial warm up the bike has a hanging idle at around 3k, but when some upper force is applied to the underside of the right side carb bank idle comes back down to normal. I have checked for vacuum leaks and found none. I have messed around with IMS and brought them out 2 fills turns, however seems to be running a bit rich with some popping when throttled. I believe I may have fixed the issue with messing around with the throttle linkage. Will check back in tomorrow if problem persists after a decent ride.

550Resto · « **Reply #25 on:** May 14, 2018, 01:41:07 PM »

So far it seems that whatever I did to adjust the throttle has worked. The idle comes down to the range that I set it to, it does shoot down, but comes down at a consistent pace. I will be leaning out the IMS a little as they are out 2 turns at the moment and way too rich judging by the popping at idle. I can't recall how to put slack I'm the actual throttle grip? Other than that she seems to be running well.

Would the too rich conditions at idle cause the bike to die?

550Resto · « **Reply #26 on:** May 26, 2018, 02:29:59 PM »

So apparently my throttle cables were not the source of my issues. I warmed the bike up and then brought her into the garage and removed the cables from the carbs. After starting the bike and setting the idle, when manually blipping the throttle at the carbs it still rises and hangs until I lift up on the right side of the carb bank. I have taken a video which can be found here:

I have no idea where to go from here. I have checked for vacuum leaks at those boots from carb to manifold and found no leaks. I have also tightened the screws that hold the bands on to the boots and no change. I'm not sure if the carb bank is sagging causing the issue? Any and all help is appreciated as I am getting to my breaking point.

TwoTired · « **Reply #27 on:** May 26, 2018, 02:57:04 PM »

Has the carb bank been vacuum sync'd?

Cheers,

BobR · « **Reply #28 on:** May 26, 2018, 04:44:43 PM »

Have you made sure all the screws that hold the carbs are tight on the plate? Maybe take the carbs off, check those mounting screws, linkage and as suggested bench sync them? Bob

550Resto · « **Reply #29 on:** May 26, 2018, 05:16:56 PM »

Hmmmm haven't double checked the screws to the plate. I had the carbs rebuilt by member Harisuluv and didn't think to check those. Carbs were vacuum synced as well.

550Resto · « **Reply #30 on:** May 28, 2018, 02:28:52 PM »

So I pulled the carbs and found 2 things that I'm not sure how to go about fixing. The first being that the choke butterflys don't seem to want to move anymore. They seem to be froze up so when I actuate the choke they don't move. They were working fine previously. Not sure the cause. The 2nd issue is that the throttle spring seems to stick a little or be sluggish when snapping back. Is there a way to loosen this up?

The carb plate that holds the carbs together was tight. I did remove it which thinking about it now might be the cause of the butterflies not moving? Still not sure why lifting up on the right side of the carb bank would have caused the idle to return to normal. I've attached a video that if anyone could give me some insight it would be greatly appreciated.

Edit: I got the butterflies to close. Seems whenever I took the plate off it did not go back on and seat all the way which caused binding when tightening the plate screws. Throttle also seems good.
I checked the boots and pulled them and put them back on so we shall see what happens.

Question: With everything installed there obviously should be no need to lift up on the carbs they should be seated where they need to be and everything holds everything in line where it should be correct? So the air box holds the carbs and the manifolds hold the boots etc.

News:

Author Topic: Idle Issue Tracked Down (Read 3681 times)