Fun with jets ..... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 07-13-2009, 05:59 PM Thread Starter
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Fun with jets .....

Ok I am asking the carb gurus here for help to see if I'm overlooking something. To start off, I did the shave and coaster bit as well as the wild exhaust pipe. I changed the jets (140 main 40 pilot) and shimmed the needles. Once I got it all together it started up fine but wouldn't rev past 4K no matter what I did. Checked for vacuum leaks and found none. After a little thinking and head scratching I removed the shims on a chance and she revved right up no problem. I rode it that way for a bit and noticed it was running on the rich side (could smell it barely). So I started playing with the jets again. I changed the new jets for the stockers (138 main 38 pilot). She started fine and idled well but as soon as I pulled out on the road she fell on her face, so I knew that wasn't going to work. After a little more thinking and head scratching, I switched out the main jet but left the pilot jets (140 mains and 38 pilots are in it now). Everything seems to be running fairly well but from a sart up to about 4K she sounds a bit off, like maybe I should go back to the 40's. But the performance she has now after 4K is amazing!
The main questions are,am I missing something here where I can lean the carbs out more with the bigger jets? Does the lack of shims have anything to do with all this? Should I just shut up and ride and deal with it? Do I try to find 39 pilots?

I await guidence.


Or a swift kick.

87 vn750at least that is what the frame #'s say
"Squirrel Bike" aka Jersey

Rat bike with a good PR agent

shaved and coastered
2 into 1 exhaust
rear 170 and front 110
Relocated R/R
custom dash with voltmeter
Spitfire windscreen
Plutonium plugs
Recovered seat without "butt hammers"
More to come
Praise to the Parts Goddess Crobins for needed things

When someone tells me "Great minds think alike" all I can think is "You Pervert"
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post #2 of 13 (permalink) Old 07-13-2009, 06:11 PM
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Did you make sure that the carb vent hose (the one at the "T") was up under the fuel tank away from any wind drafting??

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post #3 of 13 (permalink) Old 07-13-2009, 06:36 PM
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How many shims did you have in before you pulled 'em? And following niterider, when you bogged down at 4K, were you sitting in the driveway or going down the road?

C
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post #4 of 13 (permalink) Old 07-13-2009, 06:40 PM Thread Starter
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The first 4k bog was sitting in the driveway not moving. The vent tube has been tucked into the frame tube under the tank the whole time. As for shims, I made some small machine screw washers fit as shims with a thickness of .5 mm I wasn't able to find the actual shims due to parts dealers around here not really caring unless the parts in question are valued over $100.

87 vn750at least that is what the frame #'s say
"Squirrel Bike" aka Jersey

Rat bike with a good PR agent

shaved and coastered
2 into 1 exhaust
rear 170 and front 110
Relocated R/R
custom dash with voltmeter
Spitfire windscreen
Plutonium plugs
Recovered seat without "butt hammers"
More to come
Praise to the Parts Goddess Crobins for needed things

When someone tells me "Great minds think alike" all I can think is "You Pervert"
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post #5 of 13 (permalink) Old 07-13-2009, 07:01 PM
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The .5 mm looks good (just measured mine) - I think there was some debate as to whether you needed one or two, though. If you had two and removed both, try one in each carb; if you had one and removed each, try two in each carb. Also, how well did you clean the carbs when you had them off the bike? I've been pulling the air/fuel mix screw (and all associated bits, including spring, metal washer, and rubber o-ring) and cleaning out that port on each carb, since it seems prone to crud build-up. I believe that will affect fuel draw at your lower rpms.

C
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post #6 of 13 (permalink) Old 07-14-2009, 07:16 AM
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You can find good, affordable shims at Radio Shack. Though I wouldn't recommend asking the guy at the counter for carb shims to fit a Vulcan....
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post #7 of 13 (permalink) Old 07-14-2009, 05:03 PM
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Quote:
Originally Posted by dragon159 View Post
Ok I am asking the carb gurus here for help to see if I'm overlooking something. To start off, I did the shave and coaster bit as well as the wild exhaust pipe. I changed the jets (140 main 40 pilot) and shimmed the needles. Once I got it all together it started up fine but wouldn't rev past 4K no matter what I did. Checked for vacuum leaks and found none. After a little thinking and head scratching I removed the shims on a chance and she revved right up no problem. I rode it that way for a bit and noticed it was running on the rich side (could smell it barely). So I started playing with the jets again. I changed the new jets for the stockers (138 main 38 pilot). She started fine and idled well but as soon as I pulled out on the road she fell on her face, so I knew that wasn't going to work. After a little more thinking and head scratching, I switched out the main jet but left the pilot jets (140 mains and 38 pilots are in it now). Everything seems to be running fairly well but from a sart up to about 4K she sounds a bit off, like maybe I should go back to the 40's. But the performance she has now after 4K is amazing!
The main questions are,am I missing something here where I can lean the carbs out more with the bigger jets? Does the lack of shims have anything to do with all this? Should I just shut up and ride and deal with it? Do I try to find 39 pilots?

I await guidence.


Or a swift kick.
I see no mention that you adjusted the pilot screws 3-3 1/2 turns from closed, where are your screws set?

Are you using 2 shims per needle?


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote

Last edited by lance328; 07-14-2009 at 05:07 PM.
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post #8 of 13 (permalink) Old 07-20-2009, 09:57 PM Thread Starter
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Right now the screws are out 2 3/4 turns. I've been through the carbs extensively enough to think they're "sterile" but I just might go through them again. The shims I used were only 1 washer "shim" in each so I'm going to look a little harder for the right thing and try just one at .25mm and go from there. I will say that I can have the carbs removed and back in in under 15 minutes now thanks to the shave. I'm thinking that I might just need to run the screws out a little more, put 200 miles on it this weekend and seemed to get better when it was warmer, that tells me I'm a little lean.

With my lack of internet access if you wanted to call me, I'm Fairly sure Cindy has my number and hereby has my permission to release it. Or drop me a PM and I'll respond next time I can.

Thanks for the ideas!!! Back to the garage!!

87 vn750at least that is what the frame #'s say
"Squirrel Bike" aka Jersey

Rat bike with a good PR agent

shaved and coastered
2 into 1 exhaust
rear 170 and front 110
Relocated R/R
custom dash with voltmeter
Spitfire windscreen
Plutonium plugs
Recovered seat without "butt hammers"
More to come
Praise to the Parts Goddess Crobins for needed things

When someone tells me "Great minds think alike" all I can think is "You Pervert"
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post #9 of 13 (permalink) Old 07-20-2009, 11:25 PM
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Quote:
Originally Posted by dragon159 View Post
Right now the screws are out 2 3/4 turns. I've been through the carbs extensively enough to think they're "sterile" but I just might go through them again. The shims I used were only 1 washer "shim" in each so I'm going to look a little harder for the right thing and try just one at .25mm and go from there. I will say that I can have the carbs removed and back in in under 15 minutes now thanks to the shave. I'm thinking that I might just need to run the screws out a little more, put 200 miles on it this weekend and seemed to get better when it was warmer, that tells me I'm a little lean.

With my lack of internet access if you wanted to call me, I'm Fairly sure Cindy has my number and hereby has my permission to release it. Or drop me a PM and I'll respond next time I can.

Thanks for the ideas!!! Back to the garage!!
You need atleast 1.0mm in shims per needle.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote
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post #10 of 13 (permalink) Old 07-21-2009, 12:48 AM
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Just as Doug stated, you can get the washers from radio shack, ask for their assorted washer package that has the #4 washers in it and for $1.99 your out the door with more shims than you will EVER want, I am talking like 20 #4's and all the rest...LOL

Peace

"You came out of your mom looking like SHlT. She thought you were beautiful. Don't know what scared me most, your looks or her judgment."











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