Author Topic: slow return to idle (Read 2449 times)

batboy · « **Reply #25 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.

connieklr · « **Reply #26 on:** June 11, 2019, 06:51:51 pm »

Quote from: DC Concours on June 11, 2019, 04:25:11 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://i5.walmartimages.com/asr/36045e7e-f32b-4912-9283-639c007feda7_1.388497eccd5ba8ced20c7646de72fe63.jpeg?odnHeight=180&odnWidth=180&odnBg=FFFFFF

Probably made by the same people.

DC Concours · « **Reply #27 on:** June 11, 2019, 07:24:19 pm »

I am curious...Carb issues are stubborn and once clogged need surgical intervention.

Quote from: 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.

MAN OF BLUES · « **Reply #28 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.

batboy · « **Reply #29 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.

Pbfoot · « **Reply #30 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

MAN OF BLUES · « **Reply #31 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.

batboy · « **Reply #32 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

Quote from: Steve in Sunny Fla on May 22, 2015, 05:37:32 pm

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

BrianD · « **Reply #33 on:** June 12, 2019, 01:56:14 pm »

Quote from: batboy on June 12, 2019, 12:04:49 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.

connieklr · « **Reply #34 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.

batboy · « **Reply #35 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.

m in sc · « **Reply #36 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.

MAN OF BLUES · « **Reply #37 on:** June 12, 2019, 07:49:38 pm »

Quote from: batboy on June 12, 2019, 04:04:28 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...

batboy · « **Reply #38 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.

MAN OF BLUES · « **Reply #39 on:** June 12, 2019, 08:51:58 pm »

connieklr · « **Reply #40 on:** June 12, 2019, 09:03:10 pm »

Quote from: MAN OF BLUES on June 12, 2019, 07:49:38 pm

Quote from: batboy on June 12, 2019, 04:04:28 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...

Yup.

"The highest level of vacuum occurs when decelerating with the throttle closed."

batboy · « **Reply #41 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.

m in sc · « **Reply #42 on:** June 13, 2019, 01:06:36 pm »

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.

batboy · « **Reply #43 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.

Stasch · « **Reply #44 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

connieklr · « **Reply #45 on:** June 13, 2019, 03:53:28 pm »

Quote from: 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

O-Rings on the four (4) pilot air screws.

batboy · « **Reply #46 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.

m in sc · « **Reply #47 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.

Stasch · « **Reply #48 on:** June 13, 2019, 05:05:18 pm »

Quote

O-Rings on the four (4) pilot air screws.

I knew I was forgetting something!

batboy · « **Reply #49 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.