Testing Ear Shave, Rough at high RPM - Page 2 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #11 of 36 (permalink) Old 03-31-2019, 03:53 PM Thread Starter
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Hmmm, is one alignment mark width off enough to be the sole cause of a vacuum leak?

I do know that both leak, and only one is slightly misaligned.


'89 Vulcan 750 Purchased 4/12/18 @ 17805.9 miles $800
Purchased stock except for K&N Filters. Wrecked once
20969.2 miles & counting

Completed modifications:
Removed mufflers, running straight out of goats belly
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages

Planned modifications:
Ear Shave (without coasters)
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
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post #12 of 36 (permalink) Old 03-31-2019, 09:09 PM
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Hmmm, is one alignment mark width off enough to be the sole cause of a vacuum leak?

I do know that both leak, and only one is slightly misaligned.
Yes.

If there are no cracks in the rubber and no gouges in the aluminum and the boots are correctly located and the clamps tight, then there shouldn't be any leaks.

The boots must be lined up right, front to front and rear to rear.

"I need yo clothes, yo boots and yo motocycle."- Uncle Bob
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post #13 of 36 (permalink) Old 03-31-2019, 10:52 PM Thread Starter
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I'm ready to sell the bike over how difficult it is to pull the carbs on this thing! If I get it back in and it still leaks....I might just pay someone to fix it.

Even the aligned boot leaked, but I'll try once more.


'89 Vulcan 750 Purchased 4/12/18 @ 17805.9 miles $800
Purchased stock except for K&N Filters. Wrecked once
20969.2 miles & counting

Completed modifications:
Removed mufflers, running straight out of goats belly
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages

Planned modifications:
Ear Shave (without coasters)
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
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post #14 of 36 (permalink) Old 04-06-2019, 03:59 PM Thread Starter
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Ok, I resolved the vacuum leak and synchronized the carbs. I adjusted the mixture screws for fastest idle (3.5 turns). When I ease on the throttle, it goes fine from idle to 4k, then drops a bit before struggling on up to redline.

Idle throttle response is snappy though.

https://photos.app.goo.gl/gjHQGttAK35q1e8c6


'89 Vulcan 750 Purchased 4/12/18 @ 17805.9 miles $800
Purchased stock except for K&N Filters. Wrecked once
20969.2 miles & counting

Completed modifications:
Removed mufflers, running straight out of goats belly
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages

Planned modifications:
Ear Shave (without coasters)
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
post #15 of 36 (permalink) Old 04-08-2019, 12:26 PM
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Goats belly with mufflers removed able earshave? Probably should rejet.

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post #16 of 36 (permalink) Old 04-08-2019, 01:21 PM Thread Starter
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Quote:
Originally Posted by OleDirtyDoc View Post
Goats belly with mufflers removed able earshave? Probably should rejet.

Sent from my A502DL using Tapatalk
No mufflers, straight pipes out of GB. I rejetted mains to 138, and added a shim.


'89 Vulcan 750 Purchased 4/12/18 @ 17805.9 miles $800
Purchased stock except for K&N Filters. Wrecked once
20969.2 miles & counting

Completed modifications:
Removed mufflers, running straight out of goats belly
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages

Planned modifications:
Ear Shave (without coasters)
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
post #17 of 36 (permalink) Old 04-08-2019, 01:31 PM
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Quote:
Originally Posted by Jason Pittenger View Post
No mufflers, straight pipes out of GB. I rejetted mains to 138, and added a shim.
Might have to up the secondary jets too.

Sent from my A502DL using Tapatalk

ONE RATS ASS GIVEN PER POST
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 #18 of 36 (permalink) Old 04-08-2019, 05:14 PM
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Quote:
Originally Posted by OleDirtyDoc View Post
Might have to up the secondary jets too.

Sent from my A502DL using Tapatalk
Was going to say ... Maybe add shims on the needles. Couldn't hear the audio but watched the tach.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #19 of 36 (permalink) Old 04-08-2019, 11:21 PM Thread Starter
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Quote:
Originally Posted by Spockster View Post
Quote:
Originally Posted by OleDirtyDoc View Post
Might have to up the secondary jets too.

Sent from my A502DL using Tapatalk
Was going to say ... Maybe add shims on the needles. Couldn't hear the audio but watched the tach.
It starts popping above 5k. I was still adding throttle as the RPM remained relatively constant. I didn't slow down on the throttle until about 7k, so as not to overrev it.

More shims? I figured the shims I have were causing the problems.


'89 Vulcan 750 Purchased 4/12/18 @ 17805.9 miles $800
Purchased stock except for K&N Filters. Wrecked once
20969.2 miles & counting

Completed modifications:
Removed mufflers, running straight out of goats belly
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages

Planned modifications:
Ear Shave (without coasters)
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
post #20 of 36 (permalink) Old 04-09-2019, 08:15 AM
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Quote:
Originally Posted by Jason Pittenger View Post
It starts popping above 5k. I was still adding throttle as the RPM remained relatively constant. I didn't slow down on the throttle until about 7k, so as not to overrev it.

More shims? I figured the shims I have were causing the problems.
If it's still behaving as it was in the first video, it seemed lean there. But since there's no audio in the second video, you may be right and it's running rich now that the carb boots are right.

The needles are tapered and pass through the main jets, so the higher they are lifted, the more fuel flows through the main jets. Adding shims lifts the needle higher, so more fuel.

Edit: Here's an annoying video with decent graphics describing the action.


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; 04-09-2019 at 08:29 AM.
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