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Halp. Strange behavior after rejet

Started by smokestack, June 13, 2016, 09:24:52 PM

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smokestack

Help? :dunno_white: Currently running 20/60/130. Also having the problem with 20/62.5/132.5.

It ran fine before switching out the jets.

With choke off, RPMs only rise to about 6k, any further and it dies. With full choke, RPMs will go up a little higher but still dies (also dies at idle). It seems to start dying around 1/2 throttle. The air screw setting at the front of the carbs don't change anything.

Strange stuff: at full throttle, it stays at idle and blips to 3k RPM every second or so consistently. This makes me think it's something with the ignition. TPS or CDI? I had pulled off the throttle position sensor but I recalibrated according to the Haynes manual. Same behavior before and after.

tl;dr: I tried fixing it when it wasn't broke :icon_neutral: I did something stupid, $10 to gstwins if you can figure it out.

lucas

#1
Have you tried going back to the original jets?

On the wiki it says this
Quote
The stock jets for the GS500 are:
1989 - 2000: Pilot 40 (37.5 USA), Main 122.5 (yup, only two!)
2001 - 2003: Pilot 17.5, Mid Main 60, Main 127.5
2004 - 2007: Pilot 17.5, Mid Main 60, Main 130

You might be able to figure out which jets (and how many washers) are appropriate for your setup by reading the wiki page
http://wiki.gstwins.com/index.php?n=Upgrades.Rejetting

smokestack

I'm just wondering if replacing the stock 17.5 pilot with a 20 would cause an issue in the mid-range like that? And that it behaved the same with 20/62.5/132.5. Then the idle/blip behavior at full-throttle.


  • Intake boots/vacuum leaks: maybe, why would it be blipping at full throttle without stalling?
  • TPS: probably not, just adjusted per Haynes manual and resistance looks fine.
  • Pulse generator coil: no, just replaced, was working fine before rejet
  • CDI: probably not, these are usually working fine or not at all from what I'm reading
  • Float height: maybe? Measured at 14mm but possible that I was measuring it wrong.
  • Jet needle stuck: maybe? How would I check this?

The idle/blip at full-throttle is throwing me. Does it seem more like a mechanical/electrical thing than a jet configuration issue?

twocool

"It ran fine before switching out the jets."


Uh...maybe a clue? 

Just sayin"   (Been sayin' since 2010)

Yet another perfectly good bike messed up!


Cookie


smokestack

#4
I hear you, but help me understand this though: rejetting to the recommended stock config causes this issue. Then jetting lower (barely above stock) persists the issue, doesn't change it. If I go in and change the pilot from 20 to 17.5 and the issue just disappears, I'd feel more compelled to take it to an exorcist than to a mechanic. Is it reasonable to assume that small changes in jet size would cause small changes in mixture at certain RPM ranges? Changing the pilot from 17.5 to 20 causes sudden death in the mid-range? Also causes it to twitch like a heart rate monitor at full throttle?

Perfectly good in this case was actually pretty lean =/ I ran it for 3 hours after a carb rebuild and the pulse generator coil burned out. Maybe coincidence, but I know they run pretty lean stock.

lucas

Running lean can't hurt your coils as far as I know.

smokestack

Quote from: lucas on June 21, 2016, 09:59:05 AM
Running lean can't hurt your coils as far as I know.

Running hot can though?

twocool

Dude...my bike...stock...completely...never messed with carbs or anything else...51,000 miles and still running perfectly...routine service, no repairs at all.....new tires...that's it...

You guys who just can't keep your hands off the jets...you're gonna drive yourselves crazy!

This groups if full of hundreds of "re-jet problems"

Just sayin... :angel:


Cookie







Quote from: smokestack on June 21, 2016, 04:08:23 AM
I hear you, but help me understand this though: rejetting to the recommended stock config causes this issue. Then jetting lower (barely above stock) persists the issue, doesn't change it. If I go in and change the pilot from 20 to 17.5 and the issue just disappears, I'd feel more compelled to take it to an exorcist than to a mechanic. Is it reasonable to assume that small changes in jet size would cause small changes in mixture at certain RPM ranges? Changing the pilot from 17.5 to 20 causes sudden death in the mid-range? Also causes it to twitch like a heart rate monitor at full throttle?

Perfectly good in this case was actually pretty lean =/ I ran it for 3 hours after a carb rebuild and the pulse generator coil burned out. Maybe coincidence, but I know they run pretty lean stock.

The Buddha

You swapped mids ???? you put these jets in the right holes ??? You put the spring back together right so the slides lift right ? How is the floats.
I have to question your reassembly at this point, crappy jetting come in when you start fouling plugs or smelling gas or just plain sputtering and coughing with gas.

You've jetted +1 over stock, it can run like crap, make less power all over but it should do everything it did earlier. You're effectively added 2% to the fuel, its almost within the margin of error.

Cool.
Buddha.
-----------------------------------------------------------------
I run a business based on other people's junk.
-----------------------------------------------------------------

smokestack

Quote from: The Buddha on June 21, 2016, 06:11:15 PMyou put these jets in the right holes ???

Are the labels in this picture accurate? http://smg.photobucket.com/user/whanso1/media/2001-carb3MainMidPilotLocation.jpg.html

If so, I swapped the mains and mid-mains. The "main" referenced in that picture has the 60 jet right now, the "mid" has the 130. I was so certain that I pulled the original 60 out of the needle jet assembly...

Quote from: The Buddha on June 21, 2016, 06:11:15 PMYou put the spring back together right so the slides lift right ? How is the floats.

I only pulled the float bowls off to access the jets. Float height was 14mm.

jdoorn14

Yes. The labels are accurate in that pic. Refer to the parts fiche if you're in doubt.

http://www.partspitstop.com/oemparts/a/suz/506b3270f870022ba8af9a85/carburetor

For all purposes related to jet placement, your 2006 is identical to the 2007. Part 16 is the 130 Main. Note how it is directly under the jet holder while the 60 (Mid)Main is offset like the pilot.

Sounds like you swapped jet locations.
It seems it has become necessary to qualify my posts:
I am/am not trying to start an argument. This post is/is not intended to be a personal attack. I am/am not merely attempting to present a different viewpoint.

Select the words that apply to you.

smokestack

#11
Quote from: jdoorn14 on June 23, 2016, 05:06:19 AM
Sounds like you swapped jet locations.

Swapped indeed. Thank you for confirming.

smokestack

#12
$25 to gstwins

The Buddha

LOL, putting things in the wrong hole sometimes is bad.
Cool.
Buddha.
-----------------------------------------------------------------
I run a business based on other people's junk.
-----------------------------------------------------------------

smokestack

#14
[Removing inappropriate comment. Here's a nice video instead: https://youtu.be/PSKQ3ZNQ_O8?t=14]

jdoorn14

Quote from: The Buddha on June 23, 2016, 08:25:20 AM
LOL, putting things in the wrong hole sometimes is bad.
Cool.
Buddha.

It's only the wrong hole if the results aren't what you expected...
It seems it has become necessary to qualify my posts:
I am/am not trying to start an argument. This post is/is not intended to be a personal attack. I am/am not merely attempting to present a different viewpoint.

Select the words that apply to you.

smokestack

#16
Quote from: jdoorn14 on June 23, 2016, 10:20:17 AM
It's only the wrong hole if the results aren't what you expected...

-Mark Twain

lucas

Quote from: smokestack on June 23, 2016, 08:46:28 AM
[Removing inappropriate comment. Here's a nice video instead: https://youtu.be/PSKQ3ZNQ_O8?t=14]

This made me choke on a Twizzler

smokestack

Really amazing how well it runs when you put the jets in the right holes.

jdoorn14

I bet you could even put your +1 jets back in without worry too. :thumb:
It seems it has become necessary to qualify my posts:
I am/am not trying to start an argument. This post is/is not intended to be a personal attack. I am/am not merely attempting to present a different viewpoint.

Select the words that apply to you.

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