Testing Ear Shave, Rough at high RPM - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 54 (permalink) Old 03-28-2019, 11:00 PM Thread Starter
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I put my rebuilt carbs back in...then took them out to connect the throttle cable....then put them back in again.

I started it and once warm, I adjusted the mixture screws for highest RPM. (I started them at 2.5 turns). It feels like it took 2 more turns to run.

I have stock pilots, 1 shim and 138 main jets. It had good throttle response, but runs rough. I currently have no air filters on for this video. I did not add coasters or marble the vacuum lines. See video.

Thoughts? Rich? Lean?

https://photos.app.goo.gl/v5y5Kj8RMCGKjd4m6


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance

Last edited by Jason Pittenger; 03-28-2019 at 11:08 PM.
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post #2 of 54 (permalink) Old 03-28-2019, 11:09 PM
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Well I don’t have my carburetor put back together, i feel like I opened up a cascaron and expect to put the pieces of confetti back together to make a picture of a carburetor.

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post #3 of 54 (permalink) Old 03-28-2019, 11:19 PM
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Quote:
Originally Posted by Jason Pittenger View Post
I put my rebuilt carbs back in...then took them out to connect the throttle cable....then put them back in again.

I started it and once warm, I adjusted the mixture screws for highest RPM. (I started them at 2.5 turns). It feels like it took 2 more turns to run.

I have stock pilots, 1 shim and 138 main jets. It had good throttle response, but runs rough. I currently have no air filters on for this video. I did not add coasters or marble the vacuum lines. See video.

Thoughts? Rich? Lean?

https://photos.app.goo.gl/v5y5Kj8RMCGKjd4m6
They don't usually run very well with the carbs open, no filter. There are ports at the carb intake. I wouldn't do any tuning until it's got filters on.

It sounds like maybe it needs the needles shimmed more. But it may behave differently with filters. Pipes are open or punched out, right?

edit: Is that duct tape on your gas cap?

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 03-28-2019 at 11:51 PM.
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post #4 of 54 (permalink) Old 03-29-2019, 06:56 AM Thread Starter
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Originally Posted by Spockster View Post
It sounds like maybe it needs the needles shimmed more. But it may behave differently with filters. Pipes are open or punched out, right?
Pipes are otherwise stock with the mufflers removed. I'll put the filters on and try it again tonight. Thanks!

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Originally Posted by Spockster View Post
edit: Is that duct tape on your gas cap? [IMG class=inlineimg]/forum/images/smilies/smile.gif[/IMG]
HAHA no. I repainted and haven't put on the clear coat yet, so the masking tape is still on there.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
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post #5 of 54 (permalink) Old 03-29-2019, 08:58 AM
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Quote:
Originally Posted by Jason Pittenger View Post
Pipes are otherwise stock with the mufflers removed. I'll put the filters on and try it again tonight. Thanks!



HAHA no. I repainted and haven't put on the clear coat yet, so the masking tape is still on there.
Thought you were going Red Green on us.

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2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #6 of 54 (permalink) Old 03-29-2019, 09:52 AM Thread Starter
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Love that show!!!

I looked at it briefly this morning and discovered I never tightened the carb boot clams!
It may just be a vacuum leak.
That would explain why it took a lot of turns on the mixture screw to get it to run properly.

I like my neighbors too much to rev it up at 7am, so I'll try it again tonight.

Edit: I snapped a picture of two plugs (left is rear, right is front)
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'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance

Last edited by Jason Pittenger; 03-29-2019 at 09:54 AM.
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post #7 of 54 (permalink) Old 03-29-2019, 10:45 AM
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Not too lean looking so far.

Yes, the air leak could cause top end lean out and popping.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #8 of 54 (permalink) Old 03-30-2019, 07:25 AM Thread Starter
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I tightened the carb boots and tried again. It ran better, but still not quite right. I sprayed around the boots and the idle would drop, so the boots themselves are leaking.

Given the age of the bike, I think pulling my carbs to rejet opened up Pandora's box! All these old rubber pieces were fine if they weren't disturbed, but now that I have moved them, they aren't sealing again like they should!

I am going to replace the rest of the rubber on the bike, and try again.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
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post #9 of 54 (permalink) Old 03-30-2019, 04:42 PM
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proper alignment of the boots is critical. there is a bump on the boots that must *I REPEAT MUST* be lined up with the bumps on the heads at the intake ports. if you dont get that right, the boots will leak. no matter how much you tighten them
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post #10 of 54 (permalink) Old 03-31-2019, 10:47 AM
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Originally Posted by michiganteddybear View Post
proper alignment of the boots is critical. there is a bump on the boots that must *I REPEAT MUST* be lined up with the bumps on the heads at the intake ports. if you dont get that right, the boots will leak. no matter how much you tighten them
got that right. there is a post about someone's bike running at 4k while idle. i had a similar issue and my carb boots weren't lined up. i don't know how to use forums well enough to direct you to the pic i took, but it shows the alignment marks. can't upload here cuz it says i already uploaded it...

1995 VN750
Ear Shave Mod
2-Wire Mod
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SH847 R/R
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