What rejet sizes? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 07-19-2015, 11:01 AM Thread Starter
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What rejet sizes?

What size jets should i get for straight pipe exhaust and earshave/coaster mod?
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post #2 of 12 (permalink) Old 07-19-2015, 12:52 PM
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Assuming near sea level, with free-flowing pipes a minimum of 42/142 w/ 2 shims would do, maybe even higher due to the pipes. I'd start there though.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

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1989 Pontiac Firebird Formula 350
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post #3 of 12 (permalink) Old 07-19-2015, 02:59 PM
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Quote:
Originally Posted by thtanner View Post
Assuming near sea level, with free-flowing pipes a minimum of 42/142 w/ 2 shims would do, maybe even higher due to the pipes. I'd start there though.
Sounds about right.

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post #4 of 12 (permalink) Old 07-19-2015, 06:02 PM
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Here is a guide to find a starting point. http://motorcyclecarbs.com/Motorcycl...etting__W7.cfm
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post #5 of 12 (permalink) Old 07-19-2015, 06:50 PM
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Quote:
Originally Posted by smltownr View Post
Here is a guide to find a starting point. http://motorcyclecarbs.com/Motorcycl...etting__W7.cfm
I personally wouldn't use this guide. Each motorcycle is too drastically different to try to use such a generic guide like that. I'd start where we suggested and work from there, unless you have a dyno, bunch of jets, and a free afternoon; it's the best starting point.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #6 of 12 (permalink) Old 07-20-2015, 08:01 PM
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I agree that each bike is a bit different. But why is a generic starting point, decided by someone one this site years ago, better than a formula derived by testing on a dyno????? Seems like this is the Church of VN750 and the gospel from years ago is just that, the gospel. And when anyone with a different view speaks out they are blasphemers. No one here is ever going to learn anything new.
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post #7 of 12 (permalink) Old 07-20-2015, 08:15 PM
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Unless they used a VN750 on the dyno, then it isn't directly applicable...

The suggestions of 140/40 to 142/42 with 1 or 2 shims is a well tested combo that has proven results. There are threads with dyno tests if that's what you need to be happy with the general consensus on the matter. Check out threads by lance328 as he was really on top of the jetting for this particular bike's setup. If you view his old threads, people would post their setup and he'd provide the appropriate jets. They ranged from stock to 142/42 2 shims. Yes, lance did derive these from actual dyno tests to my understanding.

And really, on top of all that, my spark plugs' color doesn't lie. At least for sea level, 142/42 2 shims w/ ear shave and V&H cruizers leave my plugs a perfect color.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #8 of 12 (permalink) Old 07-21-2015, 12:55 PM
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Quote:
Originally Posted by smltownr View Post
I agree that each bike is a bit different. But why is a generic starting point, decided by someone one this site years ago, better than a formula derived by testing on a dyno????? Seems like this is the Church of VN750 and the gospel from years ago is just that, the gospel. And when anyone with a different view speaks out they are blasphemers. No one here is ever going to learn anything new.
what's with the attitude?
People have opinions and that's fine, but just because something is unchanged for years, it doesn't mean it has to change. The bike was virtually unchanged for it's 20 year production, and the info on this forum is good info that is tried and true.
There is no reason to dispute things if they actually work.
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post #9 of 12 (permalink) Old 07-21-2015, 01:24 PM
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How do you learn? Many times its someone teaching you. It's not gospel....it's truth.
It's not blasphemy....it's ignoring facts.

The vast majority of members through the years who rejeted after a earshave and exhaust swap all reported good results using 142 mains and 42 pilots. Thus...it's considered a good starting point. Some found this perfect ...others had to adjust up or down a bit. We know this. We also know unless you change the exhaust...the stock jets MIGHT work for just an earshave.
If you have proof something else works better we are all listening....

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post #10 of 12 (permalink) Old 07-21-2015, 02:30 PM
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I tried making applesauce once outta lemonade...

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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