Author Topic: Stumbles and dies when rolling the throttle  (Read 1708 times)

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Offline 01c10

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Stumbles and dies when rolling the throttle
« on: April 30, 2017, 04:05:25 pm »
All right collective minds of COG, it would be much appreciated if you would read on and come to a solution to my problem. Some background information some years back I purchased a 2001 zg1000 with 18,000 miles on it. I did what every new to them motorcycle owner would do who was excited with their recent purchase. I cruised it around and did all the fluid changes and routine maintenance one should. I put about 5000 miles on it that year. Now fast forward a few years and the romance dies and so does the maintenance. So I decide to dust her off and get back in the saddle and do some neglected maintenance and even started commuting on it again. Until one day (here is the part you’ve been waiting for) I’m about a mile from home and she starts coughing and spitting even a backfire or two. I limp home and stick her in the garage where she will sit for about a year until I decide to pull the carbs and send them to Florida. Once I received the carbs back they sat in the box for about another year until last weekend when I get the itch to throw a leg over the bike once again. I was so nervous putting the fresh set of carbs on the bike I flushed the tank so many times hoping to remove any sediment if there was any. Even bought the new gas can suggested by I think MOB. Any way I am having the same problem as before. Stumbles and dies when you roll the throttle, idles rough. Is it possible that I contaminated the freshly cleaned carbs? Or is there something else at play? I also did valves and new plugs and it has about 25,000 miles on it now.  In my defense I have had four kids and have lived in four COG regions in the last five years. If you made it through that thanks for sticking with me and I hope to hear from you.

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Re: Stumbles and dies when rolling the throttle
« Reply #1 on: April 30, 2017, 04:12:49 pm »
Lots of possibilities' and I'll let others (more knowledgeable) give you the better answers...
Without knowing more, sounds like it's starving for gas.

You didn't say how long you let it warm up with Enricher/choke opened?
Does it idle smoothly (and) on all cylinders?

Did you try running the engine with the petcock in prime?
Check for kinks in the hose...

Ride safe, Ted
« Last Edit: April 30, 2017, 04:23:42 pm by connie_rider »
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Re: Stumbles and dies when rolling the throttle
« Reply #2 on: April 30, 2017, 04:20:26 pm »
Yes check for kinked fuel line first. Also make sure all of your plug caps are pushed down on the spark plugs.
"Some days you're the windshield, and some days you're the bug" Get used to it cause thats life !!!

Offline Steve in Sunny Fla

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Re: Stumbles and dies when rolling the throttle
« Reply #3 on: April 30, 2017, 04:42:45 pm »
did you follow the instructions about inspecting / repairing the airbox, having the filter in and the door on, and the foam I provided installed in the intake? Steve
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Offline Anthony

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Re: Stumbles and dies when rolling the throttle
« Reply #4 on: April 30, 2017, 04:46:44 pm »
I just read a thread about the same thing and a vacuum line want snug...

Offline Mcfly

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Re: Stumbles and dies when rolling the throttle
« Reply #5 on: April 30, 2017, 11:32:34 pm »
Following all SISF's instructions WILL give you a properly carb'd bike. 

I've found when my Connie starts running rough the most common
culprit is a loosened spark plug cap... they seem to like to unscrew
from the vibration.  Even new wires.... 

A hesitation when the bike is cold isn't unusual.  A little enrichener
will help her along till she warms up, but it's best to let it warm up
first.
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Re: Stumbles and dies when rolling the throttle
« Reply #6 on: April 30, 2017, 11:39:18 pm »
Corroded plug wire ends?

   Tom Taylor COG#7173

Offline 01c10

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Re: Stumbles and dies when rolling the throttle
« Reply #7 on: May 01, 2017, 01:22:43 am »
Thanks for the suggestions guys, @ connie_rider I need the enricher for about thirty seconds. It idles rough and I did try running on prime. I also had an auxiliary fuel tank to sync the carbs. @ SISF yes I followed your instructions to the T. Airbox has no cracks and door is closed, foam installed. Cylinder 3 is running cooler than the rest followed by 2. 1 & 4 are nice and hot. I guess I'll be looking for a new coil pack.

Offline BrianD

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Re: Stumbles and dies when rolling the throttle
« Reply #8 on: May 01, 2017, 11:37:45 am »
With a bike that's been sitting as much as yours I would be inspecting every nook and cranny for varmints or their homes/bedding.  Also, before you throw money at a coil pack, do as others have suggested and remove the spark plug wires and re-do the plug cap and coil connections.  I had a similar problem last fall and it turned out to be a broken plug cap.

Brian Dutton
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Re: Stumbles and dies when rolling the throttle
« Reply #9 on: May 01, 2017, 01:29:06 pm »
Cylinder 3 is running cooler than the rest followed by 2. 1 & 4 are nice and hot. I guess I'll be looking for a new coil pack.

If 1 is good and 3 is bad it indicates bad wire, not bad coil pack.

30 seconds on enrichiner isn't long e'nuff on my bike.
Takes a couple of minutes before it wants to fully accept throttle.

Open each carb drain screw and see if similar amounts of fuel is in each.
Still sounds to be starving for fuel. I suspect fuel isn't reaching the cabs.

How did you sync the carbs if it has a cold #3 cylinder?

Ride safe, Ted
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Offline Katsi

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Re: Stumbles and dies when rolling the throttle
« Reply #10 on: May 01, 2017, 04:47:45 pm »
IDK if this applies to the Concourse but it does have the same carbs on it that my Ninja has so I will offer this up.  It sounds like you are stalling or running out of fuel.  Those petcocks just have a small hole that the fuel runs through and they too get clogged.  So does the vacuum side of it.  Maybe a trickle of fuel can rung through but wend you roll the throttle, it needs more fuel and it can't get any.  Also, if you let it set that long, I bet the filters on the petcock have turned to dust as well.  You should really refresh the tank, petcock and fuel lines before you mess up those newly serviced carbs.  On my Ninja, some of the jets are pressed in and if those clog up just chuck them and buy new ones because you will never clean those out.  Also, if the carbs sat in a box for that long, I bet the float needle valves have hardened as well.  Anyway, that's the route I would take first.  Hope you get it back on the road.  ;)

Offline Steve in Sunny Fla

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Re: Stumbles and dies when rolling the throttle
« Reply #11 on: May 01, 2017, 05:16:35 pm »
 I did the carbs. the carbs are fine.

 I see these kind of problems when someone has messed up the vacuum line routing, or has the plug wires going to the wrong cylinders (the cylinder order isn't the firing order) and also not getting the carbs fully seated, so vacuum leaks are present. Of course guys love to use fouled plugs to save a buck.  :-[

  From a diagnostic standpoint this started with "it won't rev" to now we know it has idle issues also.

  Diagnosing this kind of stuff can be difficult because a guy is SURE he got it "right" and the feedback he gives reflects it, but if an experienced person lays eyes on the bike, it takes about 15 seconds to say - "there's the problem, right there (points finger)"

  Case in point, did you notice how all of a sudden the coil was determined faulty? Where was the dignostics on that?

  Let's just remember that guessing is expensive and frustrating.

  Steve
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Offline Steve in Sunny Fla

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Re: Stumbles and dies when rolling the throttle
« Reply #12 on: May 01, 2017, 05:22:09 pm »

How did you sync the carbs if it has a cold #3 cylinder?

Ride safe, Ted

Ted, that's a misconception, you can easily sync the carbs when a cylinder is dead, the cylinder is still pumping air and is just along for the ride, so the sync if it's firing and the sync for it not firing is the same. the difference is that the rpms are lower given the same throttle setting when there's a dead cylinder vs all 4 firing.

  to the OP - If you had to change any of the sync settings I had any more than a tweak - max of 1/4 turn on any carb - you have a valve issue.

  HTH, Steve
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Re: Stumbles and dies when rolling the throttle
« Reply #13 on: May 01, 2017, 06:03:26 pm »
Good point. Wasn't aware of that..
Primarily; I was referring to how did he do the sync and not notice a miss.

01c10, I just came across this in another discussion.

Ok finally got the bike running good. End problem and probably the problem the whole time ended up being previous owners fault. The two larger t-fitting on the carbs that used to run into the carcoal canisiter(i believe) were capped. The bike would run and rev great for the first 2mins after it started. But would start to cut out like it was straved for gas. We eliminated the gas tank by using a fuel bottle and still had the same problem so knew it wasnt the petcock. We then decieded that the carb wasnt venting properly and possible creating a vaccum within the carb. Took the little caps off and ran great.

Is it possible you have your vent hoses capped?
Or, do you have the lines to the petcock T'd together?
  1 vacuum line opens the petcock, not 2.
Check all hoses!

Ride safe, Ted
« Last Edit: May 02, 2017, 11:53:21 am by connie_rider »
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Offline Steve in Sunny Fla

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Re: Stumbles and dies when rolling the throttle
« Reply #14 on: May 01, 2017, 08:16:59 pm »
capping the vents doesn't matter once the overflow tubes are fitted, as long as they are not blocked also. Steve
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Offline Mcfly

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Re: Stumbles and dies when rolling the throttle
« Reply #15 on: May 01, 2017, 08:24:30 pm »
capping the vents doesn't matter once the overflow tubes are fitted, as long as they are not blocked also. Steve

... and we learn something new everyday!   ;D
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Re: Stumbles and dies when rolling the throttle
« Reply #16 on: May 01, 2017, 10:34:52 pm »
capping the vents doesn't matter once the overflow tubes are fitted, as long as they are not blocked also. Steve

Another good point. I didn't think of that!!
    Wow, 2 good points in 1 day.... 
             I are impressed...   :)

Ride safe, Ted
« Last Edit: May 01, 2017, 11:05:06 pm by connie_rider »
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Offline MAN OF BLUES

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Re: Stumbles and dies when rolling the throttle
« Reply #17 on: May 01, 2017, 11:00:19 pm »
Welcome to internet carb 101... clsss please.take a seat
,now for first lesson.... e erything you KNOW is wrong.

Everything you prescribe, over the NET... is also, well... suspectedlyblowme bs.

Carry on bubba, now that the class is on board, I wish this well,  but I nderstand, truley understand, the process.... :-X :-X :truce: :truce:

Man, km glad we are freinds... I couldn't deal with this stuff anymlre, and I know how much it has to grate your nutz...

30 YEARS OF KAW.....Rich R. (the other one..)  COG 5977  JUSTAMEMBAHNOW
and if you are gonna call me names... it's MR. Analdweeb if you please...

Offline Steve in Sunny Fla

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Re: Stumbles and dies when rolling the throttle
« Reply #18 on: May 01, 2017, 11:22:43 pm »


Man, km glad we are freinds... I couldn't deal with this stuff anymlre, and I know how much it has to grate your nutz...

The new / improved / kinder / gentler bubba  :rotflmao:

 Hey get off my lawn  >:(

  Steve
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Offline Mcfly

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Re: Stumbles and dies when rolling the throttle
« Reply #19 on: May 01, 2017, 11:52:56 pm »
Welcome to internet carb 101... clsss please.take a seat
,now for first lesson.... e erything you KNOW is wrong.

Everything you prescribe, over the NET... is also, well... suspectedlyblowme bs.

At this point and time I'd like a Nurse's pass.  Emotional trauma.

Following all SISF's instructions WILL give you a properly carb'd bike. 

I'd like my participation trophy please... :o
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Offline 01c10

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Re: Stumbles and dies when rolling the throttle
« Reply #20 on: May 02, 2017, 08:40:40 am »
Thanks everyone on taking the time and working through this with me. When the bike makes it back on the priority list I'll go through the suggestions.

Offline glfredrick

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Re: Stumbles and dies when rolling the throttle
« Reply #21 on: May 11, 2017, 11:48:17 pm »
FWIW, I'm seeing the same problems on mine...

It starts fine, warms up ok on the enrichener, and will even idle down to about 1000 with no problems.

Once it is warm, I can roll on throttle quickly and it will rev easily, but roll it on slowly and it will stumble and die.

After fiddling around some, I can get it to roll on more slowly, but if I try to let out the clutch it dies instantly unless I rev it to about 5000 and dump the clutch.


Offline Jim

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Re: Stumbles and dies when rolling the throttle
« Reply #22 on: May 12, 2017, 03:56:38 pm »
capping the vents doesn't matter once the overflow tubes are fitted, as long as they are not blocked also. Steve

Just an observation:  If you install the overflow tube drain hose assembly per SISF recommendations, you've created a P-Trap which will fill with the condensed fuel vapors and effectively prevent any air flow to the bowls.