Mpg - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #1 of 29 (permalink) Old 07-18-2009, 11:56 AM Thread Starter
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Mpg

Ok this is driving me crazy. I only get about 80 miles to the tank around town which is down from 120/125. Can't find a thing wrong and bike runs fine. Mech can't find a prob either. It seems to have started after I replaced a Cam Adjuster ( or soon after) Any ideas? ( bad when gas is so pricey)
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post #2 of 29 (permalink) Old 07-18-2009, 12:47 PM
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Was the tank removed? check hoses
Cam chains tight and adjusted?
Is the choke opening and closing?
Check plugs for richness (black, wet)

For a reference, I'm running 140 jets and get a consistent 58 mpg if I don't push it.
Good luck, it's these little things that can be a pain to troubleshoot.

DT

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Last edited by dirtrack650; 07-18-2009 at 12:49 PM.
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post #3 of 29 (permalink) Old 07-18-2009, 03:25 PM
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Hey Brian, even 125 miles to a full tank isn't that great. That's under 40 mpg. Have you cleaned your system with seafoam? And since you say your mpg's have gone down since you changed your cam chain tensioners, you may have to adjust them better. I would think if they're too loose the drag could be wasting a lot of gas. Just a guess though.

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For a reference, I'm running 140 jets and get a consistent 58 mpg if I don't push it.
DT
DT that's great gas mileage. I usually get 46-48 combined city/hwy, and about 52 straight hwy. Could I get better mileage re-jetting? I live in Ft. Lauderdale which is right at sea level.

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post #4 of 29 (permalink) Old 07-18-2009, 06:45 PM
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Quote:
Originally Posted by PLPIBrian View Post
Ok this is driving me crazy. I only get about 80 miles to the tank around town which is down from 120/125. Can't find a thing wrong and bike runs fine. Mech can't find a prob either. It seems to have started after I replaced a Cam Adjuster ( or soon after) Any ideas? ( bad when gas is so pricey)
Is that with or without reserve?


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
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post #5 of 29 (permalink) Old 07-18-2009, 09:46 PM
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i can get about 125 without reserve. 51 pretty consistently and 58 if I baby her, so I pretty much get 51. your brakes or anything aren't dragging you back any are they?

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post #6 of 29 (permalink) Old 07-18-2009, 10:29 PM
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did you over oil the air filters? This will make the engine run rich.

I bet you have a fuel leak though. 80 miles per tank is really really bad. JMHO
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post #7 of 29 (permalink) Old 07-18-2009, 11:36 PM
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Quote:
Originally Posted by spiral_72 View Post
did you over oil the air filters? This will make the engine run rich.
I bet you have a fuel leak though. 80 miles per tank is really really bad. JMHO
Our carbs are CV Constant velocity, which means the fuel is metered by the amount of incomming air by the piston/diaphram assembly. If the filters are partialy clogged it would suffer in performance and not gas milage. You can have Wide Open Throttle but the piston may only open half way.

Just by switching fron 87 octain to 93 octain will cause a massive drop in MPG.


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

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post #8 of 29 (permalink) Old 07-19-2009, 02:03 AM
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Quote:
Originally Posted by rubyrick View Post
DT that's great gas mileage. I usually get 46-48 combined city/hwy, and about 52 straight hwy. Could I get better mileage re-jetting? I live in Ft. Lauderdale which is right at sea level.
I jetted because I use EMGO (K&N style) air filters and glass packs for pipes (no restrictions). Note I did say if I don't push it. Riding the interstate at 70 + or -, and the mpg goes down quick.

If you're stock, no need to re jet.

DT

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GL1100 front fender
OEM engine guard
OEM high back rest
'V-Twin' HWY pegs
Black 750 Spectre handlebars
SunPro Volt Meter (Amazon)
Maier bug shield (JCW)
Bar Ends anti-vibe (JCW)
Emgo air filters
Tank bag-Eclipse
Tail bag-FroZone Cooler
Back Rest-Igloo 6 pak cooler
WalMart Saddle Bags
R/R Relocate
Dry Splines Lubed
AGM DieHard-Sears
Gutted Goat
Sporster XL Mufflers
LED's-stop,tail,turn,marker
Pickup coil mod to .45mm
Silverstar headlight
Rotella T6
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post #9 of 29 (permalink) Old 07-19-2009, 11:33 PM Thread Starter
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Thanks for the advice guys! Cleaned the filters and changed plugs no change... No leaks...Only run 93 when I want a light cleaning...breaks are in good working order... Going to seafoam it and check the cam chains and cross my fingers. lol oh and rub a rabbits foot.Thanks again.
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post #10 of 29 (permalink) Old 07-20-2009, 12:09 AM
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This bike runs best on 87 octane, you only spend more if you use higher.
I have used 87 all the way to 104 and there is not enough power difference that the price is worth

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