Awful Gas Mileage - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
All fuel system discussion

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 06-12-2019, 09:47 AM Thread Starter
Senior Member
 
dunthyon's Avatar
 
Join Date: Dec 2017
Location: Virginia Beach, VA
Posts: 111
iTrader: (0)
 
Garage
Awful Gas Mileage

Hello! So lately my bike has been getting maybe 25-35 miles to the gallon, usually making me stop to refill at about 65 or 80 miles. I don't see any noticeable leaks, and the bike has smoke on startup that goes away pretty quickly. Also, when hot, if I turn her off she'll refuse to start up again until a very loud backfire occurs, then she'll start up a few turns after. Any ideas gentlemen?

I have a love/hate relationship with this bike I swear to God.
dunthyon is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 06-12-2019, 09:52 AM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 6,585
iTrader: (5)
   
Check the petcock vacuum line after running a bit. If it's wet, that's a problem. Oil smells like gas?

If I open the throttle on a hot start, it will backfire every time. Sometimes it needs choked just stopping long enough for gas.

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
Spockster is offline  
post #3 of 12 (permalink) Old 06-12-2019, 09:55 AM Thread Starter
Senior Member
 
dunthyon's Avatar
 
Join Date: Dec 2017
Location: Virginia Beach, VA
Posts: 111
iTrader: (0)
 
Garage
Vacuum lines are dry, oil smells like regular oil, but I may have messed up with choking on hot starts. Friend of mine said it may be the valve stem seals but I'm really trying to avoid having to try to get the engine off as I'm a parking lot mechanic lol.

I have a love/hate relationship with this bike I swear to God.
dunthyon is offline  
 
post #4 of 12 (permalink) Old 06-12-2019, 10:14 AM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 6,585
iTrader: (5)
   
Valve seals? For which problem?

If it's not running rich for some reason, see if the front brakes are dragging after being applied. Rear brake too for that matter.

Is it down on power? Running on both cylinders? 65 miles to reserve, that's about half the mpg as normal.

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
Spockster is offline  
post #5 of 12 (permalink) Old 06-12-2019, 10:26 AM Thread Starter
Senior Member
 
dunthyon's Avatar
 
Join Date: Dec 2017
Location: Virginia Beach, VA
Posts: 111
iTrader: (0)
 
Garage
From what I can tell, she's running on both cylinders. Both pipes are hot, and no loss of power is noticed, as I used to have to deal with single-cylinder running quite often (wrong petcock issue there, fixed now haha). I haven't checked the brakes though, but you're right, it isn't running rich or smoking while running so the gas usage shouldn't be so dramatic. I've seen this bike get at least 125 miles before a fillup before, and that was at a 1/4 of a tank, so I'm not sure what's up. I'll take a look at the brakes later tonight and fill it up to keep track of it again.

I have a love/hate relationship with this bike I swear to God.
dunthyon is offline  
post #6 of 12 (permalink) Old 06-12-2019, 11:00 AM
Retired USAF (IYAAYAS)
 
Chris and Shim's Avatar
 
Join Date: Mar 2010
Location: Fredrickson Wa
Posts: 614
iTrader: (0)
 
Garage
Let's check simple stuff first:

Air Filters ok?
Run a healthy dose of SeaFoam in the tank.
Is it good gas and not from a mom-n-pop store?
Drain the carbs.
Brakes not dragging?
All plugs firing?
Air pressure in tires good?
Oil good and at correct level?

TOC MCCTs
Saddlebags, hard mounted
Fork mounted tool bag (now hard mounted)
Relocated rear turn signals
LED turn signals, brake lights and running lights
LED license plate frame
Engine Guard and Highway pegs
National Cycles Low Boy Heavy Duty windshield
Home made lowers (nice)
Custom seat (made by a local guy)
Iridium plugs (DPR7EIX-9)
Shenko 230 Tour Master tires at 11,123 miles
Splines lubed at 11,123 miles
Luggage rack
Light bar with LED lights
Chris and Shim is offline  
post #7 of 12 (permalink) Old 06-12-2019, 04:45 PM
Senior Member
 
Jason Pittenger's Avatar
 
Join Date: Apr 2018
Location: Northern Illinois (Not Chicago)
Posts: 239
iTrader: (0)
 
Garage
Quote:
Originally Posted by Chris and Shim View Post
All plugs firing?
I second this!
I had a bad plug wire that was grounding on the cylinder head. It was only firing one plug. I was new to the bike and didn't know what it should have felt like. It sounded almost normal, and both pipes were hot.

This bike runs 5-25 degrees of timing advance. My truck (1 plug per cylinder) runs 14-45 degrees. Losing a plug is like retarding the timing by 10-15 degrees!


'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
Jason Pittenger is offline  
post #8 of 12 (permalink) Old 06-12-2019, 06:20 PM
Members who have donated towards server costs
 
Join Date: Nov 2007
Location: Chandler, Arizona
Posts: 2,850
iTrader: (0)
 
There are only so many possibilities here. Did this happen all at once? Has anything else changed? The gas has to be going somewhere. It is either running really rich (check the plugs) it is leaking, either outside or inside the engine (check and see if thee oil level has gone up) or something is putting a huge load on it. It is not likely the brakes. They would have overheated and failed fairly quickly, though you can put the bike on the centerstand and spin the wheels and see if they turn easily. Since you have smoke on startup, hard starting, and backfiring, I'd say it is probably running too rich. Mine has hit 35 mpg at 80 mph on the freeway many times, but goes back up to around 50 mpg when I slow down to around 65 mph. How fast are you riding?

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
VN750Rider/Jerry is offline  
post #9 of 12 (permalink) Old 06-12-2019, 07:29 PM
Super Moderator
 
Join Date: Feb 2013
Location: SW Florida
Posts: 2,451
iTrader: (5)
 
biggest thing to affect mileage is riding style.. the more you twist the right grip, the lower the mileage

2005 VN750

Sold 11-27-17
michiganteddybear is offline  
post #10 of 12 (permalink) Old 06-12-2019, 11:05 PM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 6,585
iTrader: (5)
   
We did have a poster recently with a collapsed front brake hose holding pressure. When this happens, the brake can stay applied for a varying period of time after the lever/pedal is released. One application of of the brake starts the process over.

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
Spockster is offline  
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Once registered, your User Name"cannot be changed". We can make exceptions within 7 days, but after that, it is set in stone.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome