Intermittent RPM drop - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Engine / Exhaust / Cooling
\ From the radiator, through the case and out
the exhaust. If it has to do with the cooling,
engine or exhaust, discuss it here!

 3Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 08-02-2018, 05:41 PM Thread Starter
Junior Member
 
ateam's Avatar
 
Join Date: Jun 2016
Location: Norwich, Norfolk, UK
Posts: 23
iTrader: (0)
 
Garage
Exclamation Intermittent RPM drop

Hi Vulcan owners,

I have developed strange fault and seek advice to see if itís normal.

Intermittently when I stop at a junction or lights, if I hold the clutch in the rpmís drop to 800rpm almost sounding like it will stall, if I put it into nutreal and release the clutch the rpms go back up to 1100rpm, this only happens once or twice on my journey to work most of the time it holds the 1100rpm.

Does anybody else have this problem or do you have a suggestion to cure this.

Many thanks for your help.
ateam is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 08-02-2018, 06:16 PM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 6,685
iTrader: (5)
   
Is the clutch dragging when it happens? Cable getting ready to break?

Was thinking vacuum leak or dirt hitting the pilot jets, but it doesn't happen all the time. .. and going to neutral speeds it up.

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 08-02-2018, 06:20 PM
Senior Member
 
Join Date: Nov 2015
Location: Pittsburgh, PA
Posts: 1,104
iTrader: (0)
 
Garage
Followup to Spockster's question about it possibly being a dragging clutch: if you put it in neutral and keep the clutch lever pulled, does it stay at 800?

1992 US-nonCA * tuxedo mod * r/r relocated

Vulcan slang for newcomers
Service Manual Download
Wiring Diagram + annotations * still undergoing revisions, but still more useful than the generic one. Let me know if you find mistakes or think something additional should be added
Thorn is online now  
 
post #4 of 12 (permalink) Old 08-02-2018, 06:23 PM
Old Fart
 
Knifemaker's Avatar
 
Join Date: Jun 2004
Location: Catawissa, MO
Posts: 11,679
iTrader: (4)
     
Garage
Worn or improperly adjusted clutch. Try adjusting the play in the clutch lever.
(You can adjust the cable so there is NO play in the cable and see if it solves the problem.. if it does, you have a worn or warped clutch plate(s))
If rpms are dropping while it's in gear, the clutch plates are not disengaging completely...

If You Are Not Sure If I Am Joking or Not....I AM !!Photos:
http://www.flickr.com/photos/knifemaker1954/sets/
Knifemaker is offline  
post #5 of 12 (permalink) Old 08-02-2018, 07:02 PM Thread Starter
Junior Member
 
ateam's Avatar
 
Join Date: Jun 2016
Location: Norwich, Norfolk, UK
Posts: 23
iTrader: (0)
 
Garage
Hi all,

Thanks for the replies.

The revs still drop even in neutral with clutch pulled, it doesnt affect the bike while cruising, just when I stop and pull the clutch in nuetral or with a gear selected and lever pulled.

It doesnít do it every time, but I will adjust the clutch cable at the weekend.
ateam is offline  
post #6 of 12 (permalink) Old 08-02-2018, 09:40 PM
Super Moderator
 
Join Date: Feb 2013
Location: SW Florida
Posts: 2,467
iTrader: (5)
 
mine would drop rpm when the fan kicked on when at a light, but it didnt drop that much, only 100-150 rpm drop.
JETHRO likes this.

2005 VN750

Sold 11-27-17
michiganteddybear is offline  
post #7 of 12 (permalink) Old 08-03-2018, 05:19 AM
Senior Member
 
JETHRO's Avatar
 
Join Date: Aug 2012
Location: herefordshire England
Posts: 132
iTrader: (0)
 
Garage
Quote:
Originally Posted by michiganteddybear View Post
mine would drop rpm when the fan kicked on when at a light, but it didnt drop that much, only 100-150 rpm drop.
yes MTB with a slightly weak battery this would cause it, also there is the clutch basket mod which can eliminate drag and coffee grinding noise.

Vn 750 A2 1986 rebuilt engine, crank shaft, half casing,shell bearings,con rods,rear cylinder head,oil pump,water pump ,(had ceased bearing rusted up),tie bar upgrade,clutch basket drilled,front cylinder cam chains,toc springs,stator,shaved, rectifier,agm battery,solenoid ,starter motor (used) re-spray ongoing.
JETHRO is offline  
post #8 of 12 (permalink) Old 08-03-2018, 02:15 PM
Senior Member
 
Join Date: Nov 2015
Location: Pittsburgh, PA
Posts: 1,104
iTrader: (0)
 
Garage
Quote:
Originally Posted by ateam View Post
Hi all,

Thanks for the replies.

The revs still drop even in neutral with clutch pulled, it doesnt affect the bike while cruising, just when I stop and pull the clutch in nuetral or with a gear selected and lever pulled.

It doesnít do it every time, but I will adjust the clutch cable at the weekend.
Do the cable adjustment first, but it's possible there's a weak short to ground in the clutch switch wiring (aka lockout switch) causing a drain on the electrical system when the lever is pulled. Never heard of that happening, but it's strange that the rpm drop happens when the bike is in neutral since that should remove clutch drag as a cause.
ateam likes this.

1992 US-nonCA * tuxedo mod * r/r relocated

Vulcan slang for newcomers
Service Manual Download
Wiring Diagram + annotations * still undergoing revisions, but still more useful than the generic one. Let me know if you find mistakes or think something additional should be added
Thorn is online now  
post #9 of 12 (permalink) Old 08-03-2018, 05:33 PM
Senior Member
 
kryptonianjorel's Avatar
 
Join Date: Jul 2014
Location: Washington DC
Posts: 167
iTrader: (0)
 
Could a general bad ground connection somewhere cause this to happen?
kryptonianjorel is offline  
post #10 of 12 (permalink) Old 08-03-2018, 05:38 PM
Old Fart
 
Knifemaker's Avatar
 
Join Date: Jun 2004
Location: Catawissa, MO
Posts: 11,679
iTrader: (4)
     
Garage
Quote:
Originally Posted by kryptonianjorel View Post
Could a general bad ground connection somewhere cause this to happen?
Well the clutch lever does have a switch in it. You could check there to start.
ateam likes this.

If You Are Not Sure If I Am Joking or Not....I AM !!Photos:
http://www.flickr.com/photos/knifemaker1954/sets/
Knifemaker 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