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post #1 of 14 (permalink) Old 04-20-2012, 06:12 PM Thread Starter
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Carb issues

Hi guys, I have been trying to fix an ongoing issue. When at idle if I blip the throttle the rpms drop below 1100 and eventually will climb back up sometimes idles at about 1600 and will drop down if I crack the throttle.It does this when I come to a stop at lights as well. I had 38 pilots in but switched to 40's after my ear shave this issue existed with both 38's and 40's. No amount of adjusting the air/fuel screws seems to help. Idle adjuster all the way clockwise and just barely idleing at 1100. With the air/fuel screws closed it will not idle but turning them out doesn't seem to fix anything, it will idle better but issues still exist. In fact there was some liquid coming out of the pipes at 2 turns out (clear and didnt smell like gas entirely. Also from 1100 to about 2800 rpm the bike doesn't pull like it used to. Only real change after the ear shave was making the left pipe match the right in length. Any ideas?

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post #2 of 14 (permalink) Old 04-20-2012, 07:43 PM Thread Starter
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I think I just found the source of my issue. The carb boot looks like it is on wrong slightly. Theres an impression above the top of the boot that looks to be where it should sit when correct. Will try to re-align and post if this solves it. Thanks anyways.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting
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post #3 of 14 (permalink) Old 04-23-2012, 12:26 PM Thread Starter
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So I got the carbs off this weekend and made sure the boots were seated correctly. The idle is steadier than before but the problem is still there even after letting the carbs sit all night full of sea foam. There is still the same low end problem however. Being at 5280 ft. elevation is a 40 pilot to big? I would think with the ear shave and straight pipes it should be right. Would a low end stumble/hesistation mean more fuel needed or less? It will idle currently but a slight blip of the throttle and the rpms dip below idle and slowly recover. Any help would be greatly appreciatted, thank you.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
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Apes
Stator Mod
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Paid 750.00$ for her in 2005 w/ 9k
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post #4 of 14 (permalink) Old 04-23-2012, 12:29 PM Thread Starter
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as an added note the hesitation started after I made the left exahust pipe match the right so they are the same length. After that the hesitation began in low end from about 1100 to 2500 or 3k rpm. Tried to go up from a 38 pilot to a 40 and problem still exists.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting
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post #5 of 14 (permalink) Old 04-23-2012, 02:04 PM
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By straight pipes I am guessing you mean no mufflers, no goats belly. This won't make the bike run better...actually the opposite...

But I don't think that's your Problem. If you are saying the rpms go DOWN when you open the throttle...something's seriously wrong.

If the bike runs fine above 3000 rpms then you got a jetting issue or a sticking butterfly and or diaphragm.

I'd try a 42 pilot, turn the air screws out 2-1/2 and see what that does. Might have a blocked airway in the pilot tube.

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post #6 of 14 (permalink) Old 04-23-2012, 02:14 PM Thread Starter
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Thanks for the advice KM I was hopeing you would chime in. You are correct about the pipes. They are this way out of necessity as the bike came to me with the exhaust mangled and without the goats belly. The rpms will climb when I blip the throttle but instead of settling at idle it drops below idle then will try to recover. When trying to take off from a stop it seems like im trying to ride into a strong head wind, just no ooomph until about 2500 to 3k rpm. The wierd hesitation didn't start until the pipes were matched in length. I am currently at about one turn out on my air screws. Will try to go out another turn and see what happens but it almost seems like to much fuel as there is some inside the air filters when I pulled them off. Would stumbling and hesistation be because the added back pressure making the mixture rich even with 38 pilots? Im thinking 42 would be to much for 5,280 feet.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting

Last edited by Stones750; 04-23-2012 at 02:32 PM.
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post #7 of 14 (permalink) Old 04-23-2012, 03:04 PM Thread Starter
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Tried going to 2 1/4 turns out and the idle was better but still having the same lack of power when trying to get going in first gear. I did notice theres now fuel leaking from my petcock, guess its time to rebuild that and hope my problems are over.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting
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post #8 of 14 (permalink) Old 04-23-2012, 03:45 PM
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Quote:
Originally Posted by Stones750 View Post
Tried going to 2 1/4 turns out and the idle was better but still having the same lack of power when trying to get going in first gear. I did notice theres now fuel leaking from my petcock, guess its time to rebuild that and hope my problems are over.
Kinda sounds like your only firing on one cylinder...are both pipes heating up the same?

1 turn out is not enough BTW....Set them at 2-1/2 and leave them
alone.

What did you to to the needle? (in the diaphragm)
It might be in too far?

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post #9 of 14 (permalink) Old 04-23-2012, 03:48 PM Thread Starter
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No changes to the needle since the ear shave a year ago. The mid range pulls great. The only change has been the pipe extension recently which i would think means it would be richer. I luckily have a chance to dyno it and see so I'm going to set the screws at 2 1/2 turns out and report back when I can.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting
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post #10 of 14 (permalink) Old 04-23-2012, 04:24 PM Thread Starter
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Still waiting for my dyno run but noticed it is only firing on the front cylinder untill about 2500 rpm then the rear kicks in.

86 Vn750
Coastered
De-Goated
Ears shaved
"Custom Pipes"
"Custom Seat"
Apes
Stator Mod
Malteese led Turn Signals (Rear)
Paid 750.00$ for her in 2005 w/ 9k
Currently @ 23k and counting
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