F2 Carb Cleaning

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F2 Carb Cleaning

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F2 Carb Cleaning - 8/6/2008 8:19:05 AM

WARDEN26

Posts: 5
Joined: 8/6/2008
Status: offline

Hi,

I have a 91 CBR 600 that was sitting for a year and would not start. I drained the tank and put in fresh gas then had to clean the carbs out. The bike start and runs at all speeds now, however, when I apply throttle it is slow to return to idle. I know that the rubber diaphragms were ok on the needle sliders when I disassmebled. This is my first carb cleaning, so I''m not sure what to do next.

thanks

Post #: 1

RE: F2 Carb Cleaning - 8/6/2008 12:36:07 PM

Clorox09

Posts: 34
Joined: 4/15/2008
Status: offline

When you put it all back together by any chance is the throttle cable somehow hitting the choke cable a little bit or the choke sticking?if not what about the needle screw how many turns out did you put that screw out in the carbs i put my 91 to about 2 1/2.

(in reply to WARDEN26)

Post #: 2

RE: F2 Carb Cleaning - 8/6/2008 6:01:25 PM

punkfish

Posts: 47
Joined: 6/19/2008
Status: offline

isn''t factory 1.5 turns from the bottom for the pilot screw

(in reply to Clorox09)

Post #: 3

RE: F2 Carb Cleaning - 8/7/2008 2:48:23 AM

vallip

Posts: 28
Joined: 10/28/2006
Status: offline

This can be an indication that the engine is getting air past the carbs that is the rubbers between the carbs and the cylinder head may be bad. One other thing is fuel mixture, if it is way to lean this can happen. At what RPM will this problem start ?

(in reply to punkfish)

Post #: 4

RE: F2 Carb Cleaning - 8/7/2008 1:39:19 PM

WARDEN26

Posts: 5
Joined: 8/6/2008
Status: offline

I think the cables are ok. I backed out the pilot screws two turns. The Rubber for the intake ports seemed ok, but the whole assmbly took some force to get on and seat properly.

One thing that I forgot to mention is that the small foam air filter (not sure what it is called or what it does) that is attached to the hose going to the carb body is missing. Would this cause too much air? Is this a breather mechanism of some sort?

(in reply to vallip)

Post #: 5

RE: F2 Carb Cleaning - 8/7/2008 1:44:35 PM

WARDEN26

Posts: 5
Joined: 8/6/2008
Status: offline

Hey Vallip,

The problem seems to be on the lower end of the rev range. If I opened up the throttle to say 7k or so then let off it seemed to linger at around 3.5-4k and would take a long time to return to idle.

thanks

(in reply to WARDEN26)

Post #: 6

RE: F2 Carb Cleaning - 8/7/2008 2:41:15 PM

vallip

Posts: 28
Joined: 10/28/2006
Status: offline

Ok if you are sure it is not the rubbers then I am leaning towards the pilot screws, try turning them 1/4 turn each time and see if that works, obviously there is a limit to how much you turn them out roughly 3 1/2 turns.

One thing you can do is take out a spark plug take a photo of it and post it, judging the A/F ratio from a photo is not the best but we can give that a try.

(in reply to WARDEN26)

Post #: 7

RE: F2 Carb Cleaning - 8/19/2008 7:12:46 PM

WARDEN26

Posts: 5
Joined: 8/6/2008
Status: offline

here is a pic of the #1 cylinder plug. Pic is a bit fuzzy, but the tip was covered in a white clky powder that I could wipe off, the rest of the plug looked normal. These plugs were new and only had 15 or so miles on them.

Thumbnail Image

Thumbnail Image

Attachment (2)

(in reply to vallip)

Post #: 8

RE: F2 Carb Cleaning - 8/20/2008 4:45:24 AM

woo545

Posts: 2400
Joined: 6/3/2007
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Download the service manual and follow the instructions for adjusting the pilot screws.

The starting point is approximately 1.5 turns, but can end up being more or less after adjustments are done.

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Chugga chugga WOO WOO!!!

(in reply to WARDEN26)

Post #: 9

RE: F2 Carb Cleaning - 8/20/2008 6:16:34 AM

vallip

Posts: 28
Joined: 10/28/2006
Status: offline

Hi there,

now as you say the photos are a bit fussy and difficult to read but it seems that the steel tip ( the bent part coming from the outside of the plug ) is a bit white, correct me if I am wrong, and that tells me that the bike is not getting sufficient fuel during idling. Have you tried turning the pilot screws out ?

(in reply to woo545)

Post #: 10

RE: F2 Carb Cleaning - 8/20/2008 1:28:23 PM

Rickracer

Posts: 134
Joined: 7/18/2008
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Just so you know, you dont read the ground strap, you need to read the porcelain. It looks lean too though. Id open up the pilot screws a bit and see what happens.

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A.S.E Master Auto Technician and Engine Swap Guru

(in reply to vallip)

Post #: 11

RE: F2 Carb Cleaning - 8/20/2008 4:59:42 PM

vallip

Posts: 28
Joined: 10/28/2006
Status: offline

Well I have read quite a bit on how to read spark plugs and discussed this with racers and tuners both here and in the states. Now some say that the porcelain will not tell you a thing, can be white as a bone and still be to rich, others say that the porcelain tells you how the midrange is. I have been tuning and racing for quite a few years now and have found that the porcelain is a good indication on the midrange, but saying that now that I have the F3 carbs in with the ram air system I am not getting as good of a reading on the porcelain as I did.

There are many things to consider when reading spark plugs for example how deep in to the plug the shoot is going.

< Message edited by vallip -- 8/20/2008 5:01:21 PM >

(in reply to Rickracer)

Post #: 12

RE: F2 Carb Cleaning - 8/21/2008 7:15:22 AM

Rickracer

Posts: 134
Joined: 7/18/2008
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In order to get an accurate read, you need to operate in the range you wish to calibrate for for at least a few seconds, then kill the motor in that range. For instance, if you wish to know the fuel mixture @WOT, then kill the motor clean at the end of a 1/4 mile run. If one is only wishing to know a general overall, then I''d suggest pulling and read all the plugs after a normal ride. Plug reading is an inexact science at best, but it''s cheap to do, and can be quite successful with some practice.

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Rickracer
A.S.E Master Auto Technician and Engine Swap Guru

(in reply to vallip)

Post #: 13

RE: F2 Carb Cleaning - 8/22/2008 9:00:39 AM

Chris07

Posts: 28
Joined: 11/20/2007
Status: offline

Actually you don''t read the porcelain you read the base ring. But it’s all irrelevant, as you really can’t read plugs these days. I have jetting many quads and bikes and never got it right with out a dyno and AF gauge. I have a KFX700 quad that will blacken plugs when its lean. 14:1 – 15:1 and the plugs will be black.

http://members.uia.net/pkelley2/sparkplugreading.html

(in reply to Rickracer)

Post #: 14