carburetor schenanigans - TwoWheelForum: Motorcycle and Sportbike forums
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 03-02-2007, 05:47 PM Thread Starter
 
Join Date: Apr 2006
Posts: 844
carburetor schenanigans

hey everyone, on my old ride (1989 CB-1 also known as a CB400F) I have problems starting it in colder weather (40-65 degrees). I think it may have something to do with the carburetors and the jetting/needle positioning. I know alot of these Honda motorcycles had similar carb setups, so if you know anything about this please drop a line. thanks.
CB1terror is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 03-02-2007, 05:55 PM
 
Join Date: Sep 2006
Posts: 114
normally hard starting when cold is actually created by a lean condition, sounds odd? well ideally the fuel needs to be atomised for good combustion. When engine is cold it condenses in and drips into the cylinder...

Have you tried using a quick burst of starter fluid to see if she will live? i cnt remember if the cold start system has a removeable jet...

Has the bike been sitting for any period of time? if so clean the carbs, if not, check the float height and we'll go from there!
KillerR33d is offline  
post #3 of 8 (permalink) Old 03-03-2007, 10:58 AM
 
Join Date: Aug 2004
Posts: 2,394
A CB1, I love it. This bike was great, but nobody wanted a 400cc bike back then. A four-cylinder 400 has small pistons and small carbs. The tiny jets and air bleeds can clog very quickly if it's not run during a spell of bad weather. I agree with Killer that you should clean the carbs. But right now, I would pull each spark plug in order, check them for color, and put in new plugs.
No Worries is offline  
Sponsored Links
Advertisement
 
post #4 of 8 (permalink) Old 03-03-2007, 11:08 AM Thread Starter
 
Join Date: Apr 2006
Posts: 844
sounds good. I was thinking about cleaning the carbs, but seeings how they are buried, I figured I'd do some research before hand.

Note: When its warmer outside, or the bikes already warmed up, it runs and starts perfectly fine. It only has starting/running problems when its cold.
CB1terror is offline  
post #5 of 8 (permalink) Old 03-03-2007, 11:48 AM
V-Twin Moddin
 
Gas Man's Avatar
 
Join Date: Jul 2004
Location: SE Michigan
Posts: 38,916
No worries will be the best guy to listen to on this. He not only was around during that time. Seems to be the resident carb expert.




-Chris
aka Gas Man



Was: 2002 Kaw ZX-9R
IS:


is me till the
Gas Man is offline  
post #6 of 8 (permalink) Old 03-03-2007, 08:21 PM
 
Join Date: Apr 2006
Posts: 2,142
If it only does it during the cold months, it sounds like a lean running issue due to air density to me. probably because its just not a big bike, like the 600's are, or similar bikes.
King Bob is offline  
post #7 of 8 (permalink) Old 03-03-2007, 09:24 PM
 
Join Date: Aug 2004
Posts: 2,394
Different carbs use different types of chokes to get more fuel to a cold engine. Your CB1 is the same vintage as my CBR. Pulling on my choke opens an air bleed, which pressurizes the diaphram, which allows the piston/needle to rise slightly, making for a richer mixture. If your carbs work the same, those air bleeds are probably clogged.

Cleaning carbs is an easy and fun process. Taking off and putting back on the carbs is the hard part. Of course, synchronizing, and adjusting the mixture after cleaning (and adjusting the valves) gives the bike that snap. At 1000cc's, I rarely have my throttle wide-open, but I certainly like that "snap" where the bike lunges forward with a partly-open throttle.
No Worries is offline  
post #8 of 8 (permalink) Old 03-04-2007, 12:33 PM Thread Starter
 
Join Date: Apr 2006
Posts: 844
ah yes syncing carbs. We have a '73 CB350 Four and the first time we synced those carbs we didn't have the right tools and that took forever. now we picked up some pressure gauges so syncing is a snap. Thanks for the advice No Worries, I'm gonna try that. Oh ya here is that 350 Four its one of my favorites (its got an aftermarket Jardine exhaust on it, so its sounds mean):

CB1terror is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the TwoWheelForum: Motorcycle and Sportbike forums 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










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