RPMs vary at idle - Honda Shadow Forums : Shadow Motorcycle Forum
 
LinkBack Thread Tools
post #1 of 7 (permalink) Old 12-09-2012, 08:24 PM Thread Starter
Junior Member
 
Join Date: Nov 2012
Posts: 6
RPMs vary at idle

Just bought this 2002 Honda Shadow 600. Cleaned the carb and installed a new K&N air filter and new plugs. It runs a whole lot better now.

However, all that work did not cure one problem. The RPMs will vary every couple seconds while at idle. It rides and accelerates just fine.

Any ideas? I'd hate to take it to a shop for something simple and have them charge me a bunch of money, just to say "sucker" behind my back as I walk out the door.
lugnutz is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old 12-09-2012, 08:55 PM
Senior Member
 
ZackDaniels's Avatar
 
Join Date: Dec 2006
Location: Chicago
Posts: 1,043
Garage
How much variation are we talking about here? Minor dips and bumps are reasonably normal especially if the bike is cold, but considering there's no tach on that bike it's probably not so minor if it's enough to notice...
ZackDaniels is offline  
post #3 of 7 (permalink) Old 12-09-2012, 09:10 PM
Senior Member
 
rkforrest's Avatar
 
Join Date: Jan 2011
Location: Taylors,SC
Posts: 2,404
Garage
It is a V-Twin.Smothness at Idle isnt its strong Point

03 VT750DC Spirit
00 XR650R (Sold 5/3/13)
rkforrest is offline  
post #4 of 7 (permalink) Old 12-09-2012, 11:17 PM
Senior Member
 
Scrapdog2grand's Avatar
 
Join Date: Sep 2011
Location: New Jersey
Posts: 2,257
Quote:
Originally Posted by lugnutz View Post
Just bought this 2002 Honda Shadow 600. Cleaned the carb and installed a new K&N air filter and new plugs. It runs a whole lot better now.

However, all that work did not cure one problem. The RPMs will vary every couple seconds while at idle. It rides and accelerates just fine.

Any ideas? I'd hate to take it to a shop for something simple and have them charge me a bunch of money, just to say "sucker" behind my back as I walk out the door.
You may have a small intake leak or need to richen up the idle mixture a tab, did you set your mixture srew when you where done with the cleaning and the install of the carb? also check the vacuum hose that runs from the auto fuel petcock to the rear cyclinder for a nice tight fit and no cracking in the hose.

1999 VLX
1998 SA750
1991 NSX

Scrapdog2grand is offline  
post #5 of 7 (permalink) Old 12-10-2012, 05:04 PM Thread Starter
Junior Member
 
Join Date: Nov 2012
Posts: 6
Quote:
Originally Posted by ZackDaniels View Post
How much variation are we talking about here? Minor dips and bumps are reasonably normal especially if the bike is cold, but considering there's no tach on that bike it's probably not so minor if it's enough to notice...
I'd estimate variation is 200 - 300 RPMs and it cycles every 2 to 3 seconds . . . mmmmmMMMMMMmmmmmmMMMMMMmmmmmmmMMMMMM
mmmmmMMMMMMmmmmmmmmMMMMMMMMmmmmm (humm along for a full sensory experience LOL!)
I've owned many bikes and have not experienced this before. I'd guess it has something to do with the carburetor mixture.


Quote:
Originally Posted by Scrapdog2grand View Post
You may have a small intake leak or need to richen up the idle mixture a tab, did you set your mixture srew when you where done with the cleaning and the install of the carb? also check the vacuum hose that runs from the auto fuel petcock to the rear cyclinder for a nice tight fit and no cracking in the hose.
Thanks for the tip! I'll definately check that stuff out. The bike is 10 years old and a vacuum leak might cause it. Good idea.
lugnutz is offline  
post #6 of 7 (permalink) Old 12-10-2012, 11:28 PM
Senior Member
 
ZackDaniels's Avatar
 
Join Date: Dec 2006
Location: Chicago
Posts: 1,043
Garage
That sounds somewhat normal for a bike that's been sitting for a bit. Double check your hoses and what not on the carb you just cleaned out. Be sure the breathers and what not are not clogged up... then ride it. Having purchased nothing but used bikes, I will say they tend to run a lot smoother after a heavy week of running following a garage stored past. I'm not mechanically inclined enough to say exactly why, but I imagine it's just clearing crap out of the various lines and lubricating things needing lubricated.
ZackDaniels is offline  
post #7 of 7 (permalink) Old 12-11-2012, 01:48 PM
Member
 
Join Date: Aug 2012
Location: Squamish,B.C
Posts: 203
Agree with Zack and check all your lines for leaks. Get a vacuum guage they are cheap enuf and take a few reading. The guage will find any leaks in the system!!
vonh is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



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

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









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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