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post #1 of 10 (permalink) Old 07-30-2017, 11:47 PM Thread Starter
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The Vulcan is back!

The VN750 is back at my house! Decided to take one of my extra vacation days and finally go back to dad's to clean the carbs because he never rode it after I fixed it last time. Thanks to the ear shave, the whole procedure (after what certainly appears to be a 6 year hiatus from monkeying with this thing) took less than an hour. Too lazy to drain the bad gas, I'm driving it out this week to see if the decel pops are just old gas or if I need to play with the carbs some more. But...it idles again and accelerates fine, just pops and backfires on engine braking around 2-3k rpms.

I've since sold all my bikes, so this was my first time back on two wheels in quite some time. I didn't realize just how much I missed riding the ol' girl.

Meanwhile, I've updated the links to the few posts I had here with pictures. May photobucket rot in hell...

Other than that, why the heck is this place so dang ad saturated and glitchy now?

Cheers all,

'98 VN750, Mustang Seat, F&S Engine Guards, Highway pegs, Pro-Tac backrest, Harley 58121-85B windshield lowers, Autometer 3391 voltmeter, ACCT to MCCT, pickup coils at 0.020", Coasters, National Cycle N2220, Vista Cruise Universal, Single Filter Ear Shave, Givi Monokey Sidebag Mounts, Givi E21 side bags, Knifemaker style turn signal relocation, helmet locks relocated.
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post #2 of 10 (permalink) Old 07-31-2017, 08:07 AM
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welcome back(to the "new and improved" )vn750.com.must feed the corporate sponsor

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1986/5 Vn700/750 Frankenfook cross eyed bitch "Mellisa Fayhe"
I am a BIKER and i'm proud.FREEBIRDS MC CENTRAL NY

lowered with progessive 412 10" shocks
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"I only carry when I have my pants on"Joe Robinson RIP aka Old Dog
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post #3 of 10 (permalink) Old 08-01-2017, 10:20 PM Thread Starter
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Unhappy Rear cylinder not firing between idle & 3k...

Well, got all the junk gas burnt out and put in some fresh 91 to hopefully level out the last bit that was left. Definitely seemed to pull stronger at speed and the decel popping disappeared, but the idle went to junk and the low end torque was non-existent. The low end torque was lost long before the fill up (maybe half way through the tank?) Got the idle sorted out back at the house after 3 restarts in the 8 miles between the station and the house. Played with it in the neighborhood tonight and determined that the rear cylinder isn't firing between idle and 3k. Idles fine enough, but then it's on one jug under load. After 3k, I can feel the painful lug, lug, lug turn into zoom, zoom. Then I pulled plugs, rear ones are dark & wet, front ones are dry and brown.

I did the single filter shave, upped mains to 135, and if I remember correctly (and it's been a long time), I think I did two shims to the rear cylinder's needle & one cylinder to the front. I say that now, because when I was cleaning off the needles, two shims came out with one needle, and on the other slide the washer stayed put in the bottom of the slide. At the time, I just thought, "Hmm, that's strange...I thought there were supposed to be two shims on the needles..." And just let it go at that. Upon assembly, I didn't pay any attention to which slide went to which carb and just slapped it back together.

Now, I know a shim shouldn't keep the cylinder from firing at all, so I'm scratching my head at what to chase next. All boots certainly appear to be tight, and she pulls like she's supposed to on the main jets, so I doubt it's an intake leak. I know I need to pull the carbs again to at least sanity check the needle shims. Should I just leave them out this time? The plugs are brown and not "light tan". Gas mileage last it ran was a very consistent 38 mpg. Gotta be something on the pilot jet, right?

Thanks,

'98 VN750, Mustang Seat, F&S Engine Guards, Highway pegs, Pro-Tac backrest, Harley 58121-85B windshield lowers, Autometer 3391 voltmeter, ACCT to MCCT, pickup coils at 0.020", Coasters, National Cycle N2220, Vista Cruise Universal, Single Filter Ear Shave, Givi Monokey Sidebag Mounts, Givi E21 side bags, Knifemaker style turn signal relocation, helmet locks relocated.

Last edited by abyssdncr; 08-01-2017 at 10:22 PM. Reason: Typos...
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post #4 of 10 (permalink) Old 08-01-2017, 10:46 PM
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sounds to me like it's flooding.is the float needle dirty,or is the float adjustment set right?

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1986/5 Vn700/750 Frankenfook cross eyed bitch "Mellisa Fayhe"
I am a BIKER and i'm proud.FREEBIRDS MC CENTRAL NY

lowered with progessive 412 10" shocks
rejetted for K/N Pods part#rc 2340
sportster seat

'I didn't lose my mind.i gave it away

BRING BACK WOLFIE."Peace and Carrots"RIP
"And I'm free...as a bird"John Lennon Free as a Bird
"I only carry when I have my pants on"Joe Robinson RIP aka Old Dog
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post #5 of 10 (permalink) Old 08-01-2017, 10:52 PM Thread Starter
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Never touched the float needles when I had them apart, but that sure would make sense given all the crud that was in the carbs. I'll find some clear plastic tubing and check fluid levels tomorrow before I yank them back out. Keep you posted...

Thanks!

'98 VN750, Mustang Seat, F&S Engine Guards, Highway pegs, Pro-Tac backrest, Harley 58121-85B windshield lowers, Autometer 3391 voltmeter, ACCT to MCCT, pickup coils at 0.020", Coasters, National Cycle N2220, Vista Cruise Universal, Single Filter Ear Shave, Givi Monokey Sidebag Mounts, Givi E21 side bags, Knifemaker style turn signal relocation, helmet locks relocated.

Last edited by abyssdncr; 08-01-2017 at 10:56 PM.
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post #6 of 10 (permalink) Old 08-01-2017, 10:59 PM
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also try Wolfie's blowback method before you tear it apart . it's a sticky in the carb section. could have gotten some crud in there when you were running out the old gas

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Support your local FREEBIRDS MC
1986/5 Vn700/750 Frankenfook cross eyed bitch "Mellisa Fayhe"
I am a BIKER and i'm proud.FREEBIRDS MC CENTRAL NY

lowered with progessive 412 10" shocks
rejetted for K/N Pods part#rc 2340
sportster seat

'I didn't lose my mind.i gave it away

BRING BACK WOLFIE."Peace and Carrots"RIP
"And I'm free...as a bird"John Lennon Free as a Bird
"I only carry when I have my pants on"Joe Robinson RIP aka Old Dog
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post #7 of 10 (permalink) Old 08-03-2017, 08:15 PM Thread Starter
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Tried the blow back. Won't idle off choke at all now...

Checked float level per the manual (I think...?) Rear carb, the one not firing at low rpms, was 5-6mm above the bottom of the screw. The front carb was about 3-4mm below the bottom of the screw.

Now, how the heck do you split the carbs to adjust the floats?

'98 VN750, Mustang Seat, F&S Engine Guards, Highway pegs, Pro-Tac backrest, Harley 58121-85B windshield lowers, Autometer 3391 voltmeter, ACCT to MCCT, pickup coils at 0.020", Coasters, National Cycle N2220, Vista Cruise Universal, Single Filter Ear Shave, Givi Monokey Sidebag Mounts, Givi E21 side bags, Knifemaker style turn signal relocation, helmet locks relocated.
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post #8 of 10 (permalink) Old 08-03-2017, 08:52 PM
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Sounds like the tank is distributing trash into the carbs perhaps. May want to check the petcock for equal flow out both sides to each carb while youre doing it. The ethanol turns into white creamy sludge after sitting so long.


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post #9 of 10 (permalink) Old 08-03-2017, 09:55 PM Thread Starter
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The evening's data points...

Got distracted by airplanes last night, but back at it this evening & here's what I found.

Front fuel level:



Rear fuel level:






Front float:





Rear float:






Despite the carbs actually matching the manual's description of the bench float checks of the middle of the float being between the marks, the fuel staining on the floats seems to reinforce my fluid level observations as installed.

I got stalled out at removing the float pins tonight as the sun set and needed to get the rest of the bike out of the front lawn, so that's as far as I got.

Thoughts?

'98 VN750, Mustang Seat, F&S Engine Guards, Highway pegs, Pro-Tac backrest, Harley 58121-85B windshield lowers, Autometer 3391 voltmeter, ACCT to MCCT, pickup coils at 0.020", Coasters, National Cycle N2220, Vista Cruise Universal, Single Filter Ear Shave, Givi Monokey Sidebag Mounts, Givi E21 side bags, Knifemaker style turn signal relocation, helmet locks relocated.
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post #10 of 10 (permalink) Old 08-04-2017, 07:24 AM
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On the 05 I'm working on now it was bogging down. My rear plugs were black and wet. I think my rear plugs were fouled out from all the times I tried starting it. When I got the bike it ran like crap. I put one of the good plugs from the front to the back to see what happened and it ran better so I bought new plugs and am going to try that this weekend.

"Show me a man who makes no mistakes, and I'll show you a man who doesn't do things." Theodore Roosevelt."

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