Broken Idle Adjustment Knob/Manual Idle - 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 13 (permalink) Old 04-30-2020, 03:53 AM Thread Starter
Junior Member
 
Join Date: Apr 2020
Posts: 16
iTrader: (0)
 
Broken Idle Adjustment Knob/Manual Idle

Hello everyone,

First post here. First off, I have a 2003 vn750 with 23k miles that I bought a week ago. The bike runs pretty good albeit it's got some old bike problems that I'll address one at a time through this quarantine.

This post is in regards to idle adjustment. Once the bike warms up, it'll idle anywhere between 1500 and 2000. It doesn't float between the two, it'll either be at 2000 which it seems to prefer, or drop down to 1500 at some point (seems temperature dependent?). Anyways, it seems to prefer to idle right around 2000, which is much greater than the 1100 recommended in the manual. Unfortunately, my idle adjustment knob is broken and I've heard that replacing it is both expensive and a PITA. Given that it's something you don't do too often, is there a way for me to manually adjust the idle without having to replace the cable and/or take the carbs off?

Thank you!

Last edited by Amir Razai; 04-30-2020 at 03:56 AM. Reason: submitted before finished
Amir Razai is offline  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old 04-30-2020, 11:24 PM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 7,265
iTrader: (5)
   
The idle is dependent on temperature on this one. You set the idle with the engine fully warmed up. If the ambient temperature changes a lot during a ride, the idle can be too high/low when you come to a stop.

Like if you set the idle, engine warm, on a 40 morning, when you roll to a stop at 80 in the afternoon, it's too fast.

Unfortunately, the idle set knob is the best place to adjust. You might be able set the knob all the way down to lowest rpm, then adjust the idle upward using the throttle cable, but it could be unstable, and there would be no free play in the throttle cable.

Every once in a while, a pair of low price carbs will go through ebay. Have to look every day to catch them.

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 13 (permalink) Old 05-01-2020, 12:47 AM
Senior Member
 
Join Date: Nov 2015
Location: Pittsburgh, PA
Posts: 1,213
iTrader: (0)
 
Garage
Hi Amir,
Is it just the black knob that's broken, or is it more serious than that?

If you're looking for a single adjustment, you can just spin that hex bolt head that used to be under the knob using a wrench. If you're looking to be able to adjust while in the saddle, then replacing the cable is the only way to do it.

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 13 (permalink) Old 05-01-2020, 03:21 AM Thread Starter
Junior Member
 
Join Date: Apr 2020
Posts: 16
iTrader: (0)
 
Hey Thorn!

Thanks for the reply. Seems more serious than that. The knob is fine and spins freely, but it's not attached to anything. I can see a frayed metal cable hanging off the back of the carbs that seems like what might have been attached there before. I went to the right side of the bike today and I saw what I thought might be the idle adjustment screw? It had a little metal rim covering it that seemed like it had been sanded down a bit by a mechanic in order to gain access to the screw. Is this the screw I need to turn on a one off adjustment? It looks like a very small flathead screw that is gold'ish in color? I am okay with the one time adjustments, don't want to drop $100+ on a cable I'd never use, that's like 10% of the bike lol.

Thank you!
Amir Razai is offline  
post #5 of 13 (permalink) Old 05-01-2020, 05:13 AM
Senior Member
 
Join Date: Nov 2015
Location: Pittsburgh, PA
Posts: 1,213
iTrader: (0)
 
Garage
This is going to be rough without pictures...

So, at the bottom of the carbs is the "throttle cam" that you can see move when you twist the throttle control. The idle adjustment screw should be at the bottom end of that frayed cable, which comes at a downward angle from the rear of the bike. You should see the very small threaded tip of a bolt sticking through a metal bracket which acts as an adjustable stop that the throttle cam hits against when it reaches the end of it's travel.

Presumably you could trim away the outer part of that cable and twist the inner core with pliers or whatever.

There is another screw right there on the throttle cam itself. I *THINK* that's involved with throttle balancing between the two halves of the carb, but I don't know. It's not the main idle adjust, though.

As for the screw you saw on the right side, you might have found one of the adjustments to the air/fuel mix, but you shouldn't mess with that just to lower the idle.

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 #6 of 13 (permalink) Old 05-01-2020, 03:33 PM Thread Starter
Junior Member
 
Join Date: Apr 2020
Posts: 16
iTrader: (0)
 
Hey Thorn!

Thank you again for your reply. It seems like someone may have already gone at this before I purchased the bike. Here is a picture, in the pic, I'm pointing to what I believe is the idle adjustment screw. Let me know what you think!

p.s.- plz excuse motorcycle nails. Haven't had clean nails since I bought this thing lol

Amir
Attached Thumbnails
Click image for larger version

Name:	IMG_1169.jpg
Views:	22
Size:	92.7 KB
ID:	47653  
Amir Razai is offline  
post #7 of 13 (permalink) Old 05-01-2020, 03:43 PM
Senior Member
 
mmart's Avatar
 
Join Date: Jan 2019
Location: Philadelphia
Posts: 424
iTrader: (1)
 
That looks like the air/fuel mixture screw. The idle adjustment is on the left hand side of the bike. The screw you’re pointing at is covered at the factory. Someone grounded off the covering.
mmart is online now  
post #8 of 13 (permalink) Old 05-01-2020, 04:23 PM Thread Starter
Junior Member
 
Join Date: Apr 2020
Posts: 16
iTrader: (0)
 
idle screw location

hey mmart, thanks. I watched a youtube video where someone replaced this screw with an after market and called it idle adjust, but it does appear as this is an a/f mixture screw. Is there anywhere that has instructions on replacing the idle cable?? At least I'll know what I should be turning in that case lol.

Thanks!

Amir
Amir Razai is offline  
post #9 of 13 (permalink) Old 05-01-2020, 04:36 PM Thread Starter
Junior Member
 
Join Date: Apr 2020
Posts: 16
iTrader: (0)
 
Hey Thorn!

I just went down and checked it out and I now understand where the idle screw is. Thanks for your description it made a lot of sense. Seems like the side of the cable on the left side of the bike is just frayed and hanging close to the rear cylinder. Once I get back on the bike and warm it up, I'll try to twist these frayed wires and cross my fingers that that translates to a turning screw.

Thank you for your help!

Amir
Amir Razai is offline  
post #10 of 13 (permalink) Old 05-01-2020, 04:46 PM
Senior Member
 
Join Date: Nov 2015
Location: Pittsburgh, PA
Posts: 1,213
iTrader: (0)
 
Garage
Hopefully the pliers-on-the-cable does the trick, but I imagine that cable could be completely removed if you swear at it enough, and an appropriately threaded bolt could be installed as an adjuster. (probably with a dab of blue thread locker). Let us know what works and what doesn't!

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  
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