Author Topic: Inconsistent idle  (Read 313 times)

stuo

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Inconsistent idle
« on: October 03, 2017, 12:20:43 PM »
Fellow Kymkers,

On both my '09 GV 250 and my '07 P 250 the idle will get faster the faster I've been riding. If I spend time on the freeway at 70 mph the idle will be so fast the clutch engages.

Does anyone else have this weirdness and do you have a cure or suggestion? I've thoroughly gone through both carbs so it's not that. The fast idle enricheners cut off correctly so it's not that.

Stu
GV 250
P 250
DT 300i
Vino 50
R1100RT (BMW)

CROSSBOLT

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Re: Inconsistent idle
« Reply #1 on: October 03, 2017, 01:58:16 PM »
Make sure your throttle is returning to the stop and not sticking.

Karl

Mr. Paul

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Re: Inconsistent idle
« Reply #2 on: October 03, 2017, 03:26:05 PM »
I have had the same issue. I adjusted the idle during one of the high speed runs (after pulling over.) Took a little trial and error to find the right idle for hot and cold. I suspect it has to do with the engine temps getting up a little more and affecting how the warmer air enters the combustion chamber. Or something like that. ???
2009 Kymco People 150
1993 Honda Helix

stuo

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Re: Inconsistent idle
« Reply #3 on: October 04, 2017, 02:59:14 PM »
Mr. Paul, I assume you adjusted the mechanical cable stop idle speed screw atop the carb? When I fiddle with that it goes from high idle speed to very low instantly, with nothing in between. Can you get a range of speed as you adjust the screw?  Stu
GV 250
P 250
DT 300i
Vino 50
R1100RT (BMW)

stuo

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Re: Inconsistent idle
« Reply #4 on: October 04, 2017, 03:08:25 PM »
Karl,

That was the first thing I tried: pushing down hard on the cable stop. No luck. Interesting that it does it on both my 250's, the '07 People and the '09 Grand Vista.

I think the "final solution" is to buy a People 300gti and say bye-bye to carburetors. If only the new ones came in a real color, like red or yellow or even green. Anything but black or white.

Stu
GV 250
P 250
DT 300i
Vino 50
R1100RT (BMW)

Tromper

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Re: Inconsistent idle
« Reply #5 on: October 04, 2017, 03:42:52 PM »
I had that issue on my S200, tweaked it here and there, still would do it.

I finally got it to settle after I had to replace the PAIR pipe that broke, & had one of my local mechanics go through the carb, clean it and also upped the jet size a tetch.

 My honest thought is that the PAIR pipe was cracked for a long time before that and would cause vacuum issues sometimes, but the carb work could have helped as well.
k9 S200 (Blue) "Max" (Sold)
k8 SYM HD200 "Indigo"
k7 Suzuki Burgman 650 "Ohanzee"

Mr. Paul

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Re: Inconsistent idle
« Reply #6 on: October 04, 2017, 04:53:50 PM »
Mr. Paul, I assume you adjusted the mechanical cable stop idle speed screw atop the carb? When I fiddle with that it goes from high idle speed to very low instantly, with nothing in between. Can you get a range of speed as you adjust the screw?  Stu



Yep, I just adjust the idle screw on the carb. I do get a range of rpms. Based on what your saying, I would think your low idle jet is clogged. Did you mechanically clean the jets with a wire or just spray?   I would love to have a Downtown, but I am a little tall for it. I do love my Helix though.
« Last Edit: October 04, 2017, 04:56:55 PM by Mr. Paul »
2009 Kymco People 150
1993 Honda Helix

stuo

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Re: Inconsistent idle
« Reply #7 on: October 05, 2017, 11:26:30 AM »


"Yep, I just adjust the idle screw on the carb. I do get a range of rpms. Based on what your saying, I would think your low idle jet is clogged. Did you mechanically clean the jets with a wire or just spray?   I would love to have a Downtown, but I am a little tall for it. I do love my Helix though."

Yeah, both spraying and gentle reaming was done on the carb and the jets. The fact that both my 250's are doing it says something. Maybe there's a curse on me?
GV 250
P 250
DT 300i
Vino 50
R1100RT (BMW)

Mr. Paul

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Re: Inconsistent idle
« Reply #8 on: October 05, 2017, 05:36:58 PM »
I'm out of ideas..Perhaps a Downtown in is your immediate future?  :)
2009 Kymco People 150
1993 Honda Helix

stuo

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Re: Inconsistent idle
« Reply #9 on: October 06, 2017, 07:59:49 PM »
 I bought a 2011 Downtown 300i today and I am in love! It has 3000 miles on it and runs way stronger and smoother then my carbureted 250's. And it is bright red-orange, a real color.

Many thanks for all the support and suggestions, guys. You are appreciated.

Anyone interested in a People 250?

Stu
GV 250
P 250
DT 300i
Vino 50
R1100RT (BMW)

mrbios

  • 2005 Kymco Grandvista 250cc, 18K mi, Pilot Jet #42, Main #102 (stock)
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Re: Inconsistent idle
« Reply #10 on: December 04, 2017, 01:35:49 PM »
The problem is the idle jet passage is way to small.  The smallest I have ever encountered you can barely fit a 25 gauge wire through it.  Once that passage is reduce in size to do build up from old gas the carburetor doesn't get enough gas at idle and from take off until the main jet kicks in.  You can change the idle jet and open the idle mixture screw to the max of 3 turns but you will still get the same tiny trickle of gas and the scooter will never right at idle / low speeds unless the carburetor is change or the passage is drilled out to restore it to the original size.

Fuel injection is great when implemented correctly especially in cars.  Motorcycles have taken 20 years to catch up and still there are issues with surging, stalling, won't restart, etc all the way to the present day even in high end motorcycles costing 10 to $20K and are more difficult to troubleshoot.  BMW rolled out EFI in 1986 and my 1992 K75S ran great (no staling, no uneven idle, no surging and you never touch it) until I sold it with 64K miles in 2009.  If the Kymco 250cc engines use a carb with a larger idle passage like most motorcycles you would see far fewer issues.

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