Concours Owners Group (COG) Forum

Concours Discussion (C10 / ZG1000 / 1000GTR) => Concours C10 / ZG1000 General Chat and Tech => Topic started by: batboy on June 10, 2019, 02:03:48 pm

Title: slow return to idle
Post by: batboy on June 10, 2019, 02:03:48 pm
Ok, I thought this was a throttle cable problem at first, but now I'm almost certain the carburetors need cleaned, probably gummed up pilot jets and/or needle valves. I have done at least 3 hours of searching through forum posts. But, before I pull the carbs, I wanted to make sure, because so far my track record for "correctly" diagnosing ZG1000 problems has not been good.

In the process of repairing a starting issue, I had the starter button apart several times. So, when I  got it back together, the throttle cable was binding up and sticking. I have triple check the throttle cable and return cable and lubed them as best as I could. I'm sure it's all back together correctly now. With the engine off, the throttle feels smooth and if I crack it open and then let go, the throttle snaps back with an audible click. I have the cable adjusted a little on the loose side, because I had heard too tight will cause binding. But, when it's running and fully warm up to operating temp, when you let up on the throttle, sometimes (not every time) it hangs momentarily at 3k or 4k rpm and then slowly returns to idle. The time it takes to return to normal idle rpm is variable. Manually returning the throttle does nothing to speed up the slow return to idle.

From hours of searching the forum, it appears I will need to pull the carbs off and rebuild them (probably has clogged pilot jets from sitting for 6 months). I'm trying to find the tool (3mm ball end allen hex key with a T-handle) in order to drain the carb bowls and see what happens and observe how much trash is in the bowls. I doubt draining the carbs will  magically fix the problem, but this does sometimes gets sticking needle valves to work again (although I don't think that's the main problem). I have resigned myself to the fact that I need to pull the carbs off. I have been reading how to do this and have watched SISF's videos. If you folks concur it's the carbs, I'm prepared to try doing this myself. I know there will be a half dozen guys telling me to have SISF overhaul them. If I get over my head, I can always send them to Steve. The bike was pampered prior to me buying it last summer and it ran fine last fall before I parked it. So, I think it's just gummed up a little from stale gas.

What does the forum think? I guess sooner or later you have to do carb work, it's basically a rite of passage for a  Concours owner, so I might as well start learning how to deal with it. I know for long term I need to have Steve do the overflow tubes to prevent hydrolocking. Eventually, I want to buy another set of carbs and have them done right. That will minimize down time. The petcock  was replaced not too long ago, so I'm hoping that it will hold up for a while longer. Bottom of the gas tank looks clean and rust-free. The previous owner was proud of that fact, because before I bought it, he opened the gas cap and shined a flashlight in there to show me it that it looked brand new. So, I don't think there's rust in the carbs, just gummed up from old gasoline.
Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 02:18:57 pm
If the cable closes the carbs which you can see, feel and hear then I say tackle the carbs. If you want to do it yourself great. Just make sure you don't damage anything and lose any parts. Get an egg carton so you can store the small parts.

If you do the carbs you might want to re-do the rails and change out the fuel tubing. Use OEM tubing. If you do the carbs well you won't need to buy another set. That is a waste of money. These carbs w/o any hard maintenance can easily go 50k+.


While doing the carbs I would recommend sending out the bowls to steve to get them overflowed.

Title: Re: slow return to idle
Post by: batboy on June 10, 2019, 02:42:29 pm
I forgot to mention mileage... 27k.

Yes, the cables are mechanically working fine. I can see the linkage on the outer carbs moving and returning all the way to the stops. If I crack open the throttle and suddenly let go, the cables snap back instantly and readily.

I'm trying to get the bike roadworthy for a long road trip coming up in a couple of weeks, so I need to get this fixed ASAP.

There's another reason why I might get another set of carbs, but I hesitate to mention it since it's bound to spark an off-topic discussion regarding 32mm vs. 36mm carbs.
Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 02:52:47 pm
OH. That is a very low milage bike! 1988 with only 27K. Great find. Love low milage bikes.

I had to clean my carbs and my bike at the time of purchase a few years ago only had 7k on it. The previous owners let it sit more than ride it.

Regarding the 32/34mm, you are better off putting money in other things than changing your carbs.
Title: Re: slow return to idle
Post by: Stasch on June 10, 2019, 03:42:16 pm
If pilot jets are restricted, it can cause hanging rpms on return to idle.

This is often accompanied by a turned up idle thumb screw by owners to compensate for a lag, while hanging rpms persist.

If you left untreated ethanol laced gas in there for 6 months it could have clogged some things.

Quote
I guess sooner or later you have to do carb work, it's basically a rite of passage for a  Concours owner,

Once you get them right, and proper pre-storage maintenance practices are observed, it shouldn't be an every couple of years thing.

I met one owner with 278,000 miles on his '86 C10 and the carbs had never been touched.

Mine haven't been touched for almost 15 years and 83,000 miles, and the bike starts and runs like new.  Only reason I had them off at only 16,000 miles was to put an SISF jet kit (pre 2 minute mod) in.

I have helped R&R'd several C10 carb sets from other bike's to deal with the aftermath of improper storage / maintenance.

Those memories motivate me to do proper end of season maintenance to avoid it!


Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 04:59:40 pm
This will put Sisf out of business. Don't tell us your secret.


I met one owner with 278,000 miles on his '86 C10 and the carbs had never been touched.

Mine haven't been touched for almost 15 years and 83,000 miles, and the bike starts and runs like new.

Title: Re: slow return to idle
Post by: batboy on June 10, 2019, 05:26:01 pm
Yes, I confess, I did not properly prep the bike for storage. I had not intended to leave it sitting that long, but we had a real winter this last year and I was also unexpectedly away from home for a long time early this spring. So, things did not go as planned. The gas left in the tank was probably 10% ethanol, since that's about all you can get in the middle of nowhere Kansas. But, this spring I've been using 91 octane gas with no alcohol. I usually put Sta-Bil in my GTO that sits all winter. Not sure why I didn't put it into the bike, other than I had planned to work on it some over winter (but, never did).

I have some time to work on it right now, think I'll start yanking fairing pieces off and then drain the carbs to see what junk comes out. I went into town and found a 3mm ball end hex key T-handle tool (to drain the bowls). I also stocked up on Gumout Carb Cleaner. I still need to find a heat gun before I actually pull the carbs off. I'll report back in a while.
Title: Re: slow return to idle
Post by: bajasam on June 10, 2019, 05:31:55 pm
This will put Sisf out of business. Don't tell us your secret.


if you keep up with his posts he's finished building his new ranchito and already paid it off, he most likely doesn't care if he ever see's another set of C-10 carbs ever again..
Title: Re: slow return to idle
Post by: m in sc on June 10, 2019, 05:46:31 pm
yeah, hanging idle is almost always a lean condition. time to strip and clean. (the carbs that is). check all vacuum connections, etc first.
Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 05:51:50 pm
hahahaha that is true. Kawasaki has been good to him. Never say foreign vehicles don't help the American economy. It buys a ranchito in cash plus pays off your other debts. I am in the wrong business.


if you keep up with his posts he's finished building his new ranchito and already paid it off, he most likely doesn't care if he ever see's another set of C-10 carbs ever again..
Title: Re: slow return to idle
Post by: crag antler on June 10, 2019, 07:17:17 pm
This will put Sisf out of business. Don't tell us your secret.


if you keep up with his posts he's finished building his new ranchito and already paid it off, he most likely doesn't care if he ever see's another set of C-10 carbs ever again..
Lets hope not. I’m sending mine down to him  :)
Title: Re: slow return to idle
Post by: batboy on June 10, 2019, 07:41:27 pm
The #2 carb was really hard to get a drain hose attached. Finally got it with a pair of long needle-nosed pliers. Okay, I have all four carbs drained now. Those bowls hold more than I thought. Not sure what I expected, but the gas looks perfectly fine. No crud, no gunk, no rust (no water either). Looked and smelled like normal gasoline.

In a last desperate attempt, I'll spray the outside carb linkage real good with Gumout and spritz it with WD-40 like MOB says to do. Then try running it one last time before I knuckle down and pull the carbs off.

Seems like a lot of the young crowd will insist on trying Seafoam at this point. That stuff is way overrated, in my opinion. Besides, if jets are already clogged, how is a fuel additive going to work? I'm going to pass on Seafoam.

Carbs are now empty and drain plugs tightened (not too tight, I don't want to crack the bowl seat). Do I need to set the petcock to PRI (prime) for a minute or two to refill the bowls prior to starting?
Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 08:02:54 pm
Yes prime for 45 secs
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 10, 2019, 08:52:55 pm
This will put Sisf out of business. Don't tell us your secret.


if you keep up with his posts he's finished building his new ranchito and already paid it off, he most likely doesn't care if he ever see's another set of C-10 carbs ever again..

I'm pretty sure that comment would not make Steve a happy camper.. I know he has many irons in the fire, but I don't think he will ever say he's not willing to service C10 carbs.. It was his bread and butter, and he can turn them around and do it blindfolded...


as for this "failure to drop rpm" thing, check every hose, and rubber plug, along with the boots.... vacuum leaks are the prevalent cause for failure to drop to idle.
Title: Re: slow return to idle
Post by: batboy on June 10, 2019, 09:05:54 pm
M in SC mentioned vacuum lines too. Okay, that's the next thing to do. For the boots and vacuum lines, am I mainly doing a visual inspection (looking for cracks/obvious damage) or is there a way to test them?
Title: Re: slow return to idle
Post by: DC Concours on June 10, 2019, 09:16:53 pm
MOB, I'm sure he didn't mean it like that. Just that maybe Steve wants to retire, relax, smoke some pot and enjoy his free time and not mess with carbs.
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 10, 2019, 09:23:29 pm
M in SC mentioned vacuum lines too. Okay, I that's the next thing to do. For the boots and vacuum lines, am I mainly doing a visual inspection (looking for cracks/obvious damage) or is there a way to test them?

start with the visual/flex the lines/look close thing...
Old school trick I've used also, is get your bernzamatic propane torch... (do NOT LIGHT IT), and with the bike running turn the propane on and probe the end around the hoses, boots, plugs, anyplace that "could suck in air", and if it sucks propane in, you will hear a defined change in the engine rpm...   oh, do this outside.. ok?
 :great: :rotflmao:
Title: Re: slow return to idle
Post by: batboy on June 10, 2019, 09:31:32 pm
UPDATE: The intake boots look good and clamps are tight. The air box boots look fine too. Vacuum hoses looked okay and retain some flexibility.`

QUESTION: Is #3 carb vacuum fitting supposed to be blocked off? It has a rubber cap over the barb fitting. Seems odd seeing it blocked off. Never mind, I looked it up in the service manual and the diagram on page 2-2 does show that carb being capped (except the California version and mine is not from Californification).
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 10, 2019, 11:36:54 pm
UPDATE: The intake boots look good and clamps are tight. The air box boots look fine too. Vacuum hoses looked okay and retain some flexibility.`

QUESTION: Is #3 carb vacuum fitting supposed to be blocked off? It has a rubber cap over the barb fitting. Seems odd seeing it blocked off. Never mind, I looked it up in the service manual and the diagram on page 2-2 does show that carb being capped (except the California version and mine is not from Californification).

depending on model, either 1 or 2 will be capped... (not necessarily carb #1, or carb #2), just either cali models will have one capped (usually #3), and vac lines run to petcock, air pump/reed pump valve, and cali evap can...  other models only have runs from petcock, and air valve/reed pump .... thus 2 plugs.   also, don't "Tee" any together, just makes for pulse problems.

Pull the rubber caps off, and "flex them", look for cracks, same with hoses.. they crack also.
Title: Re: slow return to idle
Post by: Stasch on June 11, 2019, 12:38:20 am
OK, time to clear up something up - I am not wanting to see SISF not have to do carb work and I am pretty sure he'll continue to see them come in. 

I had mine out 83,000 miles ago to install his products, and have sent 3 other sets to him while resurrecting other's C10's that had sat a while.

Just saying once you get it done (overflow tubes, etc) you can go a long time without having to mess with them given the proper care.

The 278,000 example I saw was 4 or 5 years ago (or more ?) at Tomah, (with 258,000 mi.) WI and Mt. Snow, VT (with 278,000 mi.)

Title: Re: slow return to idle
Post by: batboy on June 11, 2019, 12:57:29 am
I'll be working on the bike again tomorrow morning. One vacuum line(s) has a 3 way T fitting (#4 carb goes in it) while one is capped off. I need to look at the petcock vacuum hose yet. Do you think it's a vacuum hose or is this just to narrow things down and make sure the carbs really need to come off?

Not sure how serious you were about the propane torch thing, although I'm sure it's been done under many a backyard shade tree. Many moons ago, I used starting fluid to check for engine vacuum leaks. Engine rpm changes and the sound is different too. Same basic principal I guess.

No worries, Stasch, there are enough of us dingbats around to compensate for you diligent folks. We'll keep Steve busy for a while longer. Having Steve eventually do the overflow tubes is a must and many bikes haven't gotten those done yet..
Title: Re: slow return to idle
Post by: Bud on June 11, 2019, 10:04:06 am
I'll be working on the bike again tomorrow morning. One vacuum line(s) has a 3 way T fitting (#4 carb goes in it) while one is capped off. I need to look at the petcock vacuum hose yet. Do you think it's a vacuum hose or is this just to narrow things down and make sure the carbs really need to come off?

Not sure how serious you were about the propane torch thing, although I'm sure it's been done under many a backyard shade tree. Many moons ago, I used starting fluid to check for engine vacuum leaks. Engine rpm changes and the sound is different too. Same basic principal I guess.

No worries, Stasch, there are enough of us dingbats around to compensate for you diligent folks. We'll keep Steve busy for a while longer. Having Steve eventually do the overflow tubes is a must and many bikes haven't gotten those done yet..
I believe Rich was serious about using the unlit propane torch.  No mess and it should sucked in pretty easily.
Title: Re: slow return to idle
Post by: batboy on June 11, 2019, 02:57:06 pm
Apparently, the previous owner installed a fuel filter, probably at the same time the petcock was replace a few years ago. All the fuel hoses and vacuum lines that attach to the petcock look newer than the rest. I don't see anything amiss. The rubber parts all seem to be in good condition.

UPDATE: I took the fuel filter off and while it don't look bad, I tried to blow through it and it seems partially clogged (or at least I can't seem to blow much air through it). Trying to decide whether to replace it or eliminate it. I like the idea of an inline filter. Guess I'll try replacing it (if I can find one this size).
Title: Re: slow return to idle
Post by: DC Concours on June 11, 2019, 04:25:11 pm
These little inline filters are crap. Use the big napa ones.
Title: Re: slow return to idle
Post by: m in sc on June 11, 2019, 06:22:51 pm
These little inline filters are crap. Use the big napa ones.

+1 big time.

Title: Re: slow return to idle
Post by: batboy on June 11, 2019, 06:28:47 pm
Agreed, this inline filter that was used is tiny and seems partially constricted. A quick forum search showed that several folks used the NAPA Gold 3006 inline filter. So, that's the one I bought. I carefully blew into it (in the direction of the flow arrow) and it flows over twice as much air as the small one. It is a lot bigger (a tight fit), but I got it installed. Think I'll hook things back up and start it. I'm always the optimist, maybe after all this tinkering around, it will miraculously work right.

 :D
Title: Re: slow return to idle
Post by: connieklr on June 11, 2019, 06:51:51 pm
These little inline filters are crap. Use the big napa ones.

Russell and Emgo in-lines work well too. Both have the cleanable/replaceable elements. Have used both for years. Like that you can disassemble and see what your petcock filter is letting through.

https://img.jpcycles.com/product/720-698_A.jpg (https://img.jpcycles.com/product/720-698_A.jpg)

https://i5.walmartimages.com/asr/36045e7e-f32b-4912-9283-639c007feda7_1.388497eccd5ba8ced20c7646de72fe63.jpeg?odnHeight=180&odnWidth=180&odnBg=FFFFFF (https://i5.walmartimages.com/asr/36045e7e-f32b-4912-9283-639c007feda7_1.388497eccd5ba8ced20c7646de72fe63.jpeg?odnHeight=180&odnWidth=180&odnBg=FFFFFF)

Probably made by the same people.
Title: Re: slow return to idle
Post by: DC Concours on June 11, 2019, 07:24:19 pm
I am curious...Carb issues are stubborn and once clogged need surgical intervention.


Agreed, this inline filter that was used is tiny and seems partially constricted. A quick forum search showed that several folks used the NAPA Gold 3006 inline filter. So, that's the one I bought. I carefully blew into it (in the direction of the flow arrow) and it flows over twice as much air as the small one. It is a lot bigger (a tight fit), but I got it installed. Think I'll hook things back up and start it. I'm always the optimist, maybe after all this tinkering around, it will miraculously work right.

 :D
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 11, 2019, 07:52:55 pm
while I'm not a proponent of adding filters to the C10, as adding points like this can cause searching troubles at times; I say just remove all the filters, and run a fuel line... simplify what you are searching down as a cause... removing and then adding another component, is not conducive to answering the question of "root cause" of this original problem... once it runs without t filter, add one in again, if so desired... but adding parts never is advised when trying to run down a cause.. you just add in more to analyze..  it's called the K.I.S.S system

and YES, I WAS serious about using a propane source (UN LIT>>>) to run down intake vacuum leaks, it's 100x safer than spraying a flammable liquid onto your engine.. think about how long that liquid will burn if "ignited"... and compare it to the "puff" some propane will make, and dissipate almost immediately... when the source is removed from the area...  Work smart, don't do dangerous things.. the propane trick has been a staple for mechanics since the first time it was marketed... and enough people that caught fire by spraying starting fluid around, can attest to it's safety... I don't tell people to do unsafe things.  :truce: :truce:
Title: Re: slow return to idle
Post by: batboy on June 11, 2019, 09:18:23 pm
MOB, good point about KISS. But, by the time I saw your post, I had already taken it for a ride with the new fuel filter installed. As figured, no change. Idle is still hanging and dropping back slowly.

Regarding using a propane torch. Mine has apparently walked away. I can't find it. I really don't think this is a vacuum leak problem. The rubber intake couplers and vacuum hoses are in good order (flexible, not damaged, nothing loose).

The bike did not act like this when I parked it last November. This problem has to be gummed up jets due to old gas. I will quit stalling and remove the carbs. Time to go pull off the middle fairing and gas tank again. At least I know how to do that much now.
Title: Re: slow return to idle
Post by: Pbfoot on June 12, 2019, 02:30:03 am
This is the filter I use. No starvation issues. Extra insurance against the OEM petcock screen that seems to fail every 2 years.  https://www.napaonline.com/en/p/FIL3006 (https://www.napaonline.com/en/p/FIL3006)
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 12, 2019, 02:35:36 am
I'll re-iterate.. lack of returning to idle, has almost nothing to do with jetting... it's an air issue.
Title: Re: slow return to idle
Post by: batboy on June 12, 2019, 12:04:49 pm
Yesterday, I took the tank and middle fairing back off back off to prepare for pulling the carbs off. That's as far as I got.

Ok MOB, I hear you. I will do more checking for a vacuum leak and if I have to, I'll run into town and get a new propane torch if I can't find my old one. During my forum search though, I found 2 or 3 cases where they had the same problem I'm having and it turned out to be plugged pilot jets. But, after sleeping on it, I realize that I should not be too hasty with the troubleshooting process. I'll report back once I've done more checking. If I don't find a smoking gun with an unignited propane torch, then what's next?

MOB says this problem is usually a lock of air, what about the air filter? Maybe I should check it. I believe the previous owner told me it had a K&N filter.

PBfoot, I did buy a NAPA Gold 3006 filter, but it's been changed a little and doesn't look exactly like what you posted (see photo).

UPDATE: Found my torch kit, but there was no cylinder, so I will go pick up propane this morning.

UPDATE part 2: I removed the air filter, it was a K&N. It was so clean it looked brand new. A common problem with K&N is that some people over oil them. This one was fine, no excessive oil, it looked good. NOTE: After a little thought, I realize the air filter or air box would not cause a vacuum leak.

here is a thread that matches my problem:

http://forum.cog-online.org/concours-c10-zg1000-general-chat-and-tech/throttle-appears-to-be-'sticking'/msg181036/#msg181036 (http://forum.cog-online.org/concours-c10-zg1000-general-chat-and-tech/throttle-appears-to-be-'sticking'/msg181036/#msg181036)

Lots of posting lately about vacuum leaks, which I have never seen to be the case.



Title: Re: slow return to idle
Post by: BrianD on June 12, 2019, 01:56:14 pm
UPDATE part 2: I removed the air filter, it was a K&N. It was so clean it looked brand new. A common problem with K&N is that some people over oil them. This one was fine, no excessive oil, it looked good.

You should probably check your airbox.  Search the forum for info - there have been cases reported of K&N filters causing the airbox to split open due to their thickness.  Might not be causing your problem, but could be adding to it.  Pretty sure Steve has a video on repairing it if you find it split.
Title: Re: slow return to idle
Post by: connieklr on June 12, 2019, 02:57:49 pm
A split air box is on the wrong side of the carbs to create a "slow to return to idle" issue.

Do the propane thing to see if that reveals anything.
Title: Re: slow return to idle
Post by: batboy on June 12, 2019, 04:04:28 pm
Yeah, I got sidetracked, let's forget about the air box for now, because it could not cause a vacuum leak anyway. However, I did need to inspect the air box and filter to be thorough. The box looks okay and filter is clean. So, I can check that off the list.

I bought a bottle of propane. I will concentrate on checking the 4 rubber intake carb holders (where it seals around the carbs and the head) and any vacuum hose that originates from the carbs. The vacuum ports on #1 carb and #4 carb each connects to a T fitting and then go to the reed valves or whatever those things are called (bumps in the valve cover over by the spark plugs). The vacuum port for #3 carb is capped off and #2 carb vacuum hose goes to the petcock. Did I miss anything? I shouldn't need to worry about vent hoses other than to make sure they aren't blocked.

UPDATE: I checked for vacuum leaks as advised with a propane torch. I got a good hiss of propane coming out and waved the nozzle around all of the above listed places with the bike idling. There was no change in idle speed or exhaust tone. There was no fire or smoke. Nothing. My conclusion is there are no vacuum leak.
Title: Re: slow return to idle
Post by: m in sc on June 12, 2019, 06:59:35 pm
aside from the previously mentioned possible airbox cause, a clogged pilot, clogged fuel screw circuit (idle mixture screw) can cause this issue as well. or a sticking slide. I think you need to pull the carbs and inspect.
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 12, 2019, 07:49:38 pm

UPDATE: I checked for vacuum leaks as advised with a propane torch. I got a good hiss of propane coming out and waved the nozzle around all of the above listed places with the bike idling. There was no change in idle speed or exhaust tone. There was no fire or smoke. Nothing. My conclusion is there are no vacuum leak.

your complaint was the "bike doesn't return to idle"...
checking with the propane, at idle, does not provide the same situation as when the bike is revved up, held, and the throttle is released..
you need to re-create the same vacuum scenario, while using the propane...  to see if it sucks in ... when the vacuum is higher... :truce: :truce:
Title: Re: slow return to idle
Post by: batboy on June 12, 2019, 08:29:31 pm
I get what you're saying, MOB. Maybe it doesn't leak vacuum at idle, but does at a certain rpm. On the other hand the rubber parts all look to be in great condition and I discovered that nothing leaks at idle.

It's a moot point now, the carbs are off and sitting on the bench. I didn't find a heat gun in the nearest town, I'll have to order one from Amazon or drive an hour to Home Depot. So, instead I rolled the bike out onto the driveway, under the Kansas summer sun for a while and that made the rubber couplers more pliable.

I will start another thread to discuss what I need to have and do to clean up the carbs and get them operational again. I'm not attempting a complete overhaul. If I start finding missing or worn out parts, then I'll need to rethink this endeavor. Right now, I need to learn Zen and the fine art of motorcycle carburetor maintenance.
Title: Re: slow return to idle
Post by: MAN OF BLUES on June 12, 2019, 08:51:58 pm
(https://i.pinimg.com/originals/98/36/56/983656266c254c30caebb067b21b3f1a.jpg)

 :great:
Title: Re: slow return to idle
Post by: connieklr on June 12, 2019, 09:03:10 pm

UPDATE: I checked for vacuum leaks as advised with a propane torch. I got a good hiss of propane coming out and waved the nozzle around all of the above listed places with the bike idling. There was no change in idle speed or exhaust tone. There was no fire or smoke. Nothing. My conclusion is there are no vacuum leak.

your complaint was the "bike doesn't return to idle"...
checking with the propane, at idle, does not provide the same situation as when the bike is revved up, held, and the throttle is released..
you need to re-create the same vacuum scenario, while using the propane...  to see if it sucks in ... when the vacuum is higher... :truce: :truce:

Yup.

"The highest level of vacuum occurs when decelerating with the throttle closed."
Title: Re: slow return to idle
Post by: batboy on June 13, 2019, 01:00:04 pm
This set of carbs were amazingly clean for being 31 years old. I examined the bowl screws with a magnifying glass and they don't have a mark on them. I would say these carbs have never been worked on. I carefully flipped the slides up and they work smoothly.

So, I removed the bowl from #1 carb. The inside looked good and again, amazingly clean. My guess was clogged pilot jets since that's the smallest jet in the carb and is often the first to get gummed up (especially if gas with alcohol sat unused for a few months). Sure enough, I backed the jet out and eyeballed it with a bright light and magnifying glass. It was skimmed over and clogged. I don't want to stick anything down there, especially metal that might scratch the jet. Fortunately, a shot of Gumout carb cleaner and a shot of compressed air did the trick.

I'm debating on how to proceed. The manly DIY part of me says to completely disassemble and clean everything (no solvents on rubber parts of course). But, I can't stress how clean things look. No matter what I do, I'll catch flack, but the realistic side of me that wants to be riding is leaning to just cleaning the pilot jets and calling it a day. I'd like to reinstall and see if the problem is fixed. If so, then I isolated the problem. If not, I'll have to eat crow,

One thing I thought of, this bike was sold new at a Boulder, Colorado dealership. Think it's got the smaller 122 high altitude main jets (normally the used 125 main jets)? Guess I'll go out and pull one of the main jets and personally see for myself.
Title: Re: slow return to idle
Post by: m in sc on June 13, 2019, 01:06:36 pm
 :beerchug:

you dont have to split the bank, but spray through every air jet opening at the bellmouth and make sure they all flow. (of course with the slides out) and the air fuel screws as well, take them out and clean them. youre 90% of the way there, might as well make sure everything is clear for a trouble free summer. Id jump up tot he 125's if for no other reason than to offset the ethanol mixture now in fuels.
Title: Re: slow return to idle
Post by: batboy on June 13, 2019, 01:59:21 pm
It has 125 main jets, so they are not the high altitude jets after all. Looks like stock normal jets, which is fine. I'd rather be a little rich than too lean,

I have to take a timeout and do yard work for a few hours. That'll give me time to decide how much I should do. I'm leaning toward baby steps. Besides, I'm likely to end up with a different carb set on here anyway.
Title: Re: slow return to idle
Post by: Stasch on June 13, 2019, 03:26:03 pm
I know it sounds easier to spray carb cleaner without disassembling, but keep in mind that even with the carb diaphrams out, there are still rubber parts in there such as:

*Orings on fuel feed 'T' between carbs 2 & 3
*Orings on fuel tubes connecting carbs 1 & 2  and  3 & 4
*Orings on vent tubes between 1 & 2  and  3 & 4
*Aircut valves
*Orings in the air cut valve covers
Rubber tips on float valves
**Possible Orings on butterfly valve shafts

*parts that can't be removed without splitting the rack.
**don't know of a way to R&R these - but its something to be aware of
Title: Re: slow return to idle
Post by: connieklr on June 13, 2019, 03:53:28 pm
I know it sounds easier to spray carb cleaner without disassembling, but keep in mind that even with the carb diaphrams out, there are still rubber parts in there such as:

*Orings on fuel feed 'T' between carbs 2 & 3
*Orings on fuel tubes connecting carbs 1 & 2  and  3 & 4
*Orings on vent tubes between 1 & 2  and  3 & 4
*Aircut valves
*Orings in the air cut valve covers
Rubber tips on float valves
**Possible Orings on butterfly valve shafts

*parts that can't be removed without splitting the rack.
**don't know of a way to R&R these - but its something to be aware of

O-Rings on the four (4) pilot air screws.
Title: Re: slow return to idle
Post by: batboy on June 13, 2019, 04:16:00 pm
I did the trimming around the lawn, but decided to put off mowing until tomorrow since the  ground is  still damp.

Had to get back at the carbs. The pilot jet in #2 carb was a tiny pinpoint. After a shot of cleaner and air, the jet looked twice as big. Both #3 and #4 were still passable, although both were oval shaped when held up to the light.

The bowls required almost no clean up, a tiny speck of dark sediment in the very bottom by the drain. I'm doing old school hand cleaning. Spray a little cleaner onto a spot on the microfiber cloth. Then use fingers to gently clean metal parts.

I took the diaphragms out and checked for holes. They looked good. Floats looked good and all seemed to be lined up the same when I got down low and eyeballed them. I took the pins out and cleaned the needle valve and seat (tiny blast of carb cleaner followed by compressed air).

I took the main jet out of #1 carb to check size. The jets looked fine, so I didn't bother taking any of the other main jets out. I decided to leave the pilot/idle screws alone too. You're supposed to replace the o-ring and I didn't have a rebuild kit. I'm assuming it's set to the factory settings.

I'm going to put it all back together before I mess around and screw something up.

Last night I did some searching on other forums (other models and even other brands) about hung idle and slow return. It's fairly common and almost always turns out to be clogged pilot jets.
Title: Re: slow return to idle
Post by: m in sc on June 13, 2019, 04:59:14 pm
yup. you dont always need to replace the o-ring if its in good shape. im pretty sure you got it sorted.  :motonoises:
Title: Re: slow return to idle
Post by: Stasch on June 13, 2019, 05:05:18 pm
Quote
O-Rings on the four (4) pilot air screws.

I knew I was forgetting something!
Title: Re: slow return to idle
Post by: batboy on June 13, 2019, 05:33:14 pm
Ok, I've unclogged the pilot jets and have minimally cleaned the carbs. They are now fully reassembled. Shucks, I don't even have any extra parts left over this time. Pretty sure I didn't mess anything up (too bad). I need to take a break and watch Steve's carb installation video again before I get too froggy.
Title: Re: slow return to idle
Post by: Bud on June 13, 2019, 05:42:19 pm
 :popcorncouple:
Title: Re: slow return to idle
Post by: batboy on June 13, 2019, 08:38:01 pm
Carbs are back on the bike. The throttle cables threw a big fit and battled me for a while. Then, muscling the carbs onto the rubber couplers was a struggle too (I still don't have a heat gun). I need to tighten the clamps down, adjust the throttle cables, and reattach the choke cable. I should be able to finish up this evening. But first, it's time to rest my back and put my feet up for a few minutes. Maybe drink a cold one.

 :beerchug:
Title: Re: slow return to idle
Post by: connie_rider on June 13, 2019, 10:00:43 pm
(Your wife's) Hair dryer work's well as a heat gun for this job.
  {Don't tell my wife I sed that}... :67:

Ride safe, Ted

Title: Re: slow return to idle
Post by: DC Concours on June 13, 2019, 10:06:06 pm
Great idea. Didn't think of this when I was doing mine.

(Your wife's) Hair dryer work's well as a heat gun for this job.
  {Don't tell my wife I sed that}... :67:

Ride safe, Ted


Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 12:19:00 am
I discovered that the two inner air box couplers were not completely on the carbs. So, I had another fight on my hands, and then, I also had trouble rolling those spring retainers into place.

I was messing with the throttle cable adjustment when the skeeters swarmed in. I put on that Deep Woods Off and those little blood suckers just held their noses and charged right in. No more work tonight.

I'll finish it up tomorrow morning. Hopefully it'll start.
Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 04:25:24 pm
This bike is a time machine. I went out to spend a minute adjusting the throttle cables and suddenly it's an hour into the future. The round rubber stops on the frame that the front of the tank slides onto would not stay on, even with duct tape. I ended up zip tying them. I notice it's another hour into the future. I tweak the fuel filter so it sits under the tank a bit better. Poof, I'm teleported another hour into the future again.

UPDATE: I started the motor briefly, but shut it off immediately. It sounded unusually loud. Maybe I didn't get one of the air box boots all the way on. I struggled with those center ones. The more I think about it, the noise did sort of sound like when you start a car with the air cleaner off. You got that loud sucking noise, especially with the choke on. Dunno, I'm going to take the tank back off and look closely. It did start though, so that was encouraging.
Title: Re: slow return to idle
Post by: crag antler on June 14, 2019, 05:01:56 pm
It may be too late for you but 2 tips.
New air box boots will do wonders for you.
Tire spoon works great for putting boots onto carbs with no worry of punctures.
Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 05:17:25 pm
The couplers between the carbs and engine all look good. Clamps are all nice and tight. On #2 carb, the air boot is not all the way on in one spot, but it don't look like it would leak. I'll mess with that a little and triple check everything else again.

Dumb question. Would the engine sound noticeably louder without the middle fairing on? I started it once back in October with the middle fairing off, but I really don't remembering the bike sounding louder. But, I wasn't being paranoid about whether I got the carbs back together correctly, like today.
Title: Re: slow return to idle
Post by: m in sc on June 14, 2019, 05:27:22 pm
you'll hear more noise for sure. just try it. see if it feels better and the hanging idle issue is resolved.
Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 06:26:30 pm
I got the air box boot slid a tad more onto Carb #2. If I do this again, I'll get new boots like Steve suggested in his video. On the other side, it had felt like all the intake couplers were tight when checked with a screwdriver, but when I looked at the screws on the clamps to make sure they were nearly bottomed out, two on #4 carb were not even close to being all the way tight. Rust on the clamp threads made me think the screws were tight. I loosened that clamp up and sprayed it with PB Blaster. I worked the aqdjustor screw in and out a few times. Now the clamp screws down all the way. Hope that was the problem.

I looked everything over real close one final time and saw gas hanging in drips on the bottom of #4 carb. "Oh guano!" I felt my chest clench up and my heart started pounding, I worried that I was going to have the "big one" (deadly heart attack). "I'm coming, Elizabeth!"  Wait a minute, that "gas" looks funny (odd not haha funny). It's yellowish and looks oily. I dip a finger in it and smell. It's PB Blaster (LOL). I had just used it on the nearby clamp and excess ended up there. Whew!

Guess I'll put the tank back on and see what happens.
Title: Re: slow return to idle
Post by: DC Concours on June 14, 2019, 07:01:15 pm
Make a video, make a video. I can barely stand the suspense. Good job doing all this and giving us a blow by blow.
Title: Re: slow return to idle
Post by: Pbfoot on June 14, 2019, 07:52:52 pm
Make sure the PAIR valve  big rubber hose is inserted into the top of the airbox. Will make quite a racket if you forget.  Don't ask me how I know.
Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 08:25:47 pm
Should have a web cam since this is almost in real time.

PBfoot, you nailed it, dude. That tube must have pulled out of the box when I moved the box back to make more room for the carb removal. Doh, seems so obvious now. Unplugged hole in the air box and open tube coming from the valve cover. Thank you!

Unable to find anything else wrong, I started it up and warmed it up enough to move the choke completely off. It's idling much smoother, but it's idling at about 1500 rpm instead of 1000. I'm assuming the idle dropped too low to stay running, thus the previous owner probably turned up the idle to max to compensate. That would suggest the pilot jets were getting clogged even before I bought it and let it set for 6 months. I'm sure that didn't help.

I suspect the higher and smoother idle means I fixed the problem, but I need to ride it to make sure. The idle rarely hung when parked, it usually did it while cruising around, Guess I'll test ride it without the middle fairing.
Title: Re: slow return to idle
Post by: batboy on June 14, 2019, 09:18:49 pm
Fixed! It's running perfect now. I learned a lot from this adventure. Thanks to all that helped.

 :great:

Title: Re: slow return to idle
Post by: Bud on June 14, 2019, 10:36:10 pm
 :beerchug: :great: :motonoises: :motonoises:
Title: Re: slow return to idle
Post by: Pbfoot on June 15, 2019, 10:47:15 am
You're welcome. Glad I could help.
Title: Re: slow return to idle
Post by: batboy on June 15, 2019, 12:39:03 pm
If your bike seems to have a rough idle (rpm "lopes" or fluctuates) and idle speed is low, then you might have clogged pilot jets (causes a lean condition). Many if not most Concours owners will adjust the idle speed knob to compensate for the drop in idle speed. That is a valuable clue if you just recently bought one like I did. If the idle adjustment knob had been adjusted to the max position, that's a red flag. It suggests there's a problem. The pilot jet is not only used for idle, but covers low speeds up to 3000-3500 rpm. Problems with the pilot jets mean poor low speed performance. Hard starting is another clue. Be careful, a vacuum leak might have the same symptoms. I recommend checking for vacuum leaks prior to carb removal. MOB has good info about looking for vacuum leaks.

Why do pilot jets clog up so easy? They are the smallest jets in the carb, so they are the first to get gummed up. Untreated gasoline (especially if it contains alcohol) will go stale after a few weeks and start causing problems. If your bike sat for a long time, there's a good chance you'll have some issues with gunk in the carbs from the bad gas. Where is the pilot jet? Under the bowl next to the main jet. I'd say carb removal is pretty much required. Technically, some people have removed the bowls from the carbs with them still on the bike, but you'd need small hands of a child and special tools. So, not impossible, but realistically, forget it. Carb removal is a bit intimidating, but if I can do it, anyone can.
Title: Re: slow return to idle
Post by: batboy on June 15, 2019, 07:14:13 pm
I decided to do the fuel gauge variable resistor mod to finish up. This will be fun to calibrate now.

Got the fairing back on and took the bike for a 30 mile test ride. Runs great. I can't get over how smooth it idles now compared to before.

Here's a photo of my bike out in the middle of nowhere Kansas during my test ride. My bike always seems to brighten up the landscape.
Title: Re: slow return to idle
Post by: m in sc on June 15, 2019, 09:22:01 pm
(https://media3.giphy.com/media/vMnuZGHJfFSTe/giphy.gif)


glad its sorted.  :great: