Author Topic: Carb problem, Bike cannot go to idle.HELP~~ (Read 3788 times)

Marco83 · « **on:** November 16, 2006, 07:35:20 AM »

Hi all,
Recently I got a 2nd hand cb400f carb off from ebay.
The carb look quite nice to me and I bought 4 set of keyster carb rebuild kit from ebay to
rebuild the carb. The carb is fully rebuild( change every part) and clean. But once I install the carb onto my bike, my bike fire up right away(My old carb cannot get my bike start).

But once the bike start, the RPM will run up to 2-3k..After a while the bike just die off.
When I start again but still encounter the same problem, the bike just cannot go to idle mode.

I already try to adjust the idle screw (the main one), but seen no different.
How do i sync to make it right?Btw i got no vaccum meter. I have read the FAQ for Carb but still dun understand how it work...

Really need help on this issue.
Pls advise..
The attach photo was taken after the rebuild.

Thank
Marco

bryanj · « **Reply #1 on:** November 16, 2006, 07:52:18 AM »

You need to do a full service (points,timing,tappets,camchain) then use vacuum gauges on the carbs

Klark Kent · « **Reply #2 on:** November 16, 2006, 07:54:07 AM »

also check spark plugs caps and wires for old-badness.

-KK

Marco83 · « **Reply #3 on:** November 16, 2006, 07:58:36 AM »

last year my bike still running with my old carb..

Marco83 · « **Reply #4 on:** November 16, 2006, 08:00:06 AM »

Quote from: Klark Kent on November 16, 2006, 07:54:07 AM

also check spark plugs caps and wires for old-badness.

-KK

Had check everything..Bike always start with a few kick.
But just cannot enter idle mode..

dave550K · « **Reply #5 on:** November 16, 2006, 11:43:53 AM »

I had the same problem and it was a dead battery. Just a thought.
Dave

mb3000gt · « **Reply #6 on:** November 16, 2006, 01:09:52 PM »

did you bench sync them after rebuilding? what are the air screws set at? are you sure the rubber boots are tight?

Marco83 · « **Reply #7 on:** November 16, 2006, 03:56:26 PM »

Quote from: dave550K on November 16, 2006, 11:43:53 AM

I had the same problem and it was a dead battery. Just a thought.
Dave

it work fine when i put in another carb..

Marco83 · « **Reply #8 on:** November 16, 2006, 03:59:17 PM »

Quote from: mb3000gt on November 16, 2006, 01:09:52 PM

did you bench sync them after rebuilding? what are the air screws set at? are you sure the rubber boots are tight?

nope, never set and how to set the Bench sync??
nope also, how to set the air screws?
rubber boots are tight!''

thank
marco

heffay · « **Reply #9 on:** November 16, 2006, 04:00:47 PM »

did you add the idle grease?

Hockers Choppers · « **Reply #10 on:** November 16, 2006, 04:10:09 PM »

Turn your air screws in all the way and then back them out 1 1/2 turns and see what you have then. If that doesn't work you may have some blocked idle circuit's. take off the carbs again and try blowing carb cleaner thru all of the small passages.

Marco83 · « **Reply #11 on:** November 16, 2006, 04:11:13 PM »

Quote from: heffay on November 16, 2006, 04:00:47 PM

did you add the idle grease?

what is idle grease?
really not very good at this.
pls advise..

Thank

Hockers Choppers · « **Reply #12 on:** November 16, 2006, 04:12:28 PM »

Quote from: heffay on November 16, 2006, 04:00:47 PM

did you add the idle grease?

Come on man!

Marco83 · « **Reply #13 on:** November 16, 2006, 04:14:53 PM »

Quote from: Hockers Choppers on November 16, 2006, 04:10:09 PM

Turn your air screws in all the way and then back them out 1 1/2 turns and see what you have then. If that doesn't work you may have some blocked idle circuit's. take off the carbs again and try blowing carb cleaner thru all of the small passages.

I will try this tonight.

Marco83 · « **Reply #14 on:** November 16, 2006, 04:15:13 PM »

Quote from: Hockers Choppers on November 16, 2006, 04:12:28 PM

Quote from: heffay on November 16, 2006, 04:00:47 PM
did you add the idle grease?
Come on man!

Bob Wessner · « **Reply #15 on:** November 16, 2006, 04:44:10 PM »

Marco,

He was pulling your leg. Not fair.

Marco83 · « **Reply #16 on:** November 16, 2006, 04:50:19 PM »

Quote from: Bob Wessner on November 16, 2006, 04:44:10 PM

Marco,

He was pulling your leg. Not fair.

guys pls help!

upperlake04 · « **Reply #17 on:** November 16, 2006, 06:47:47 PM »

Quote

how to set the Bench sync??

Marco - I don't know if the 400F has a non-adjustable slide in the #2 carb, but remove the caps from the tops of the carbs and look at the linkages. If #2 doesn't have the adjuster screw, use the main idle adjust thumbcrew to lower its slide to just friction fit a drill bit (or something else). Then adjust the other slides with their linkage adjuster screws so all are the same. Bench synch is not as accurate as a vacuum synch but it will get you close. Good luck!

Klark Kent · « **Reply #18 on:** November 16, 2006, 06:54:37 PM »

does size of drill bit matter? i used a 1/16" bit, and youve got what looks like a 1/4"... is there a suggested spec?
-KK

upperlake04 · « **Reply #19 on:** November 16, 2006, 07:06:57 PM »

KK - no, it doesn't matter. The idea is to adjust them to the same height - then use the thumbscrew to adjust the idle.

Marco83 · « **Reply #20 on:** November 16, 2006, 07:12:44 PM »

Quote from: upperlake04 on November 16, 2006, 07:06:57 PM

KK - no, it doesn't matter. The idea is to adjust them to the same height - then use the thumbscrew to adjust the idle.

will that work after adjust?
Can you post the step by step with the pic?i' very noob on bike.
Really a big thank if you can do that!

Marco

miles nowhere · « **Reply #21 on:** November 16, 2006, 08:16:35 PM »

you could also have an air leak somewhere between the carbs. If you broke the carbs down completely, they might not have gone back together tight enough.

Marco83 · « **Reply #22 on:** November 16, 2006, 09:34:57 PM »

Quote from: miles nowhere on November 16, 2006, 08:16:35 PM

you could also have an air leak somewhere between the carbs. If you broke the carbs down completely, they might not have gone back together tight enough.

What are those i need to look for?i mean where are those place properly will encounter air leak?

Thank
Marco

oldbiker · « **Reply #23 on:** November 17, 2006, 02:53:12 AM »

He means check the rubber connecting tubes for good fit..

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Author Topic: Carb problem, Bike cannot go to idle.HELP~~ (Read 3788 times)

dave550K

upperlake04

upperlake04