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Carbs and Fuel System
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post #1 of 22 (permalink) Old 12-31-2013, 02:46 PM Thread Starter
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my turn to pick y'alls brains

ok here is the skinny

94 vn750 bone stock less than 4k miles that has been sitting for 7 yrs due to a floppy shifter

i split the cases and replaced the tie rod

engine has no leaks of any sort

carbs have been completely disassembled and dipped in chem dip

all diaphragms look good or are new checked for pin holes with flashlight and magnifying glass

stock jets 132 and 38 totally cleaned

all boots are tight and proper no leaks

floats adjusted to proper levels

air fuel mix is at 2 1/2 turns out


and here is the problem the bike runs awesome on the road with plenty of giddy up and no stumbles on acceleration even at wide open however at idle she stumbles and dies like she is running lean

also she runs better when on full choke

what do you guys think

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post #2 of 22 (permalink) Old 12-31-2013, 03:27 PM
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Quote:
Originally Posted by new rider 9984 View Post
ok here is the skinny

94 vn750 bone stock less than 4k miles that has been sitting for 7 yrs due to a floppy shifter

i split the cases and replaced the tie rod

engine has no leaks of any sort

carbs have been completely disassembled and dipped in chem dip

all diaphragms look good or are new checked for pin holes with flashlight and magnifying glass

stock jets 132 and 38 totally cleaned

all boots are tight and proper no leaks

floats adjusted to proper levels

air fuel mix is at 2 1/2 turns out
Did you do the carbs, NR?

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Originally Posted by new rider 9984 View Post
and here is the problem the bike runs awesome on the road with plenty of giddy up and no stumbles on acceleration even at wide open however at idle she stumbles and dies like she is running lean

also she runs better when on full choke

what do you guys think
Did you mean 'full' choke and is that at cruise, WFO or idle? How does it run on the pilot circuit above idle? The first 1/4 of throttle.
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post #3 of 22 (permalink) Old 12-31-2013, 03:33 PM Thread Starter
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i did the carbs myself and surprisingly for them taking a 7 yr nap they were not too bad

the bike runs smoother at idle when fully choked so i am thinking it is running lean but adjusting the air fuel mix does nuthing for it

there are no stumbles at 1500 rpm or higher

all vac lines are new and tight

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i got my helmet but it sure makes licking the windows a chore

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post #4 of 22 (permalink) Old 12-31-2013, 03:35 PM Thread Starter
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on a side note this thing has more acceleration than my bike which has bigger jets a more open intake and v&h pipes go figure

however im sure my bike has lower compression due to many more miles

<this post is totally unrelated to the problem at hand>

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Sucks getting old but it beats not getting old.

i got my helmet but it sure makes licking the windows a chore

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post #5 of 22 (permalink) Old 12-31-2013, 04:01 PM
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Quote:
Originally Posted by new rider 9984 View Post
i did the carbs myself and surprisingly for them taking a 7 yr nap they were not too bad

the bike runs smoother at idle when fully choked so i am thinking it is running lean but adjusting the air fuel mix does nuthing for it

there are no stumbles at 1500 rpm or higher

all vac lines are new and tight
ok, here comes a guess.

Barring the possibility you swapped the main air jet(s) and the pilot air jet(s), it is probably something in the pilot circuit between the first 2 throttle bore orifices. With the throttle closed you will see the first orifice on the floor of the bore. As you open the throttle, the blade will uncover the other 2 or 3 orifices. All in a line. The first orifice is the only one exposed to engine vacuum at idle. This should be the culprit. It is the farthest from the fuel source.

If the rest of the orifices were not open/clean, the bike would not run well at any low throttle openings.

If I had this, I would probably pull the close off valve assemblies and the pilot gas jets. I have the nozzles for the blow gun necessary to backwards blow out the pilot circuit. About 25# air regulated.

My best guess. HTH
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post #6 of 22 (permalink) Old 12-31-2013, 04:03 PM
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on a side note this thing has more acceleration than my bike which has bigger jets a more open intake and v&h pipes go figure
I would expect that.
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post #7 of 22 (permalink) Old 12-31-2013, 04:13 PM Thread Starter
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Quote:
Originally Posted by wmsonta View Post
ok, here comes a guess.

Barring the possibility you swapped the main air jet(s) and the pilot air jet(s), it is probably something in the pilot circuit between the first 2 throttle bore orifices. With the throttle closed you will see the first orifice on the floor of the bore. As you open the throttle, the blade will uncover the other 2 or 3 orifices. All in a line. The first orifice is the only one exposed to engine vacuum at idle. This should be the culprit. It is the farthest from the fuel source.

If the rest of the orifices were not open/clean, the bike would not run well at any low throttle openings.

If I had this, I would probably pull the close off valve assemblies and the pilot gas jets. I have the nozzles for the blow gun necessary to backwards blow out the pilot circuit. About 25# air regulated.

My best guess. HTH
sounds logical but i did acid dip everything metal for over 24 hours and blew everything out

could a slightly bent needle cause the same symptoms cause i dont remember checking them to see if they were bent i just cleaned them and stuck them back in

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Originally Posted by denny6006 View Post
Sucks getting old but it beats not getting old.

i got my helmet but it sure makes licking the windows a chore

cell phone number for anyone who needs it 214-516-1738

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post #8 of 22 (permalink) Old 12-31-2013, 04:22 PM
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sounds logical but i did acid dip everything metal for over 24 hours and blew everything out

could a slightly bent needle cause the same symptoms cause i dont remember checking them to see if they were bent i just cleaned them and stuck them back in
First, the pilot circuit gets slightly smaller the farther away from the gas jet. They really should be blown out backwards. The cut off valves should be removed when using air/solvents on the pilot circuit. The cut off valve vacuum port is in the roof of the throttle bore straight above the pilot idle port on the floor. Any solvent/vapor available to this port will go directly to the cut off diaphragm.

The needle will have nothing to do with idle. Even if the slide is stuck raised.

Did you remove the air jets to soak the carbs? The pilot and main air jets would be hard to distinguish at a glance.

Last edited by wmsonta; 12-31-2013 at 04:33 PM.
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post #9 of 22 (permalink) Old 12-31-2013, 04:26 PM
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Dirty petcock?

Will it run on a bottle? ,, bypass the tank

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post #10 of 22 (permalink) Old 12-31-2013, 04:38 PM
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Make sure your diaphram needles are in the right carb. Different size needles front and back!
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