« previous next »
Pages: [1]   Go Down

Author Topic: The carb with a mind of it's own.  (Read 775 times)

0 Members and 1 Guest are viewing this topic.

nwest4

  • Guest
The carb with a mind of it's own.
« on: April 05, 2009, 06:46:01 PM »
Hi folks, long time since I have posted.  I have a question on a 78 CB750K.  Have gone thru the carbs completely and blown out all passages and jets and bench synched as close as possible.  Also have set the points, timing and valve adjustment.  My dilemma is when synching the carbs, I get all four matched up pretty close to perfect with a nice idle and all. When I whack the throttle to verify settings once idled back down, No. 1 carb is out of synch rather badly.  It does this almost every time after opening the throttle quickly.  It also seems to take an inordinate amount of adjustment again to get her back to the other carb settings.  I have checked for vacuum leaks and anything else I can think of.  Sticking slide?  Carb gods mad at me?  This bike is currently running pod air filters which I hate, but have not gone back to stock airbox yet due to lack of funding.  I would'nt think this is the issue but who knows.  I have used my gauges on numerous other bikes in the past and has worked like a champ on all of them, but this one is kicking my a** right now.  Any suggestions greatly appreciated.  Thanx, Neil ???
Logged

Offline OldSchool_IsCool

  • Really feeling like an
  • Old Timer
  • ******
  • Posts: 4,349
  • WARNING: Objects in mirror appear to be LOSING!
Re: The carb with a mind of it's own.
« Reply #1 on: April 05, 2009, 06:59:00 PM »
Stripped adjusting screw or nut?
Logged
Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline eurban

  • Master
  • *****
  • Posts: 1,625
Re: The carb with a mind of it's own.
« Reply #2 on: April 05, 2009, 07:11:42 PM »
After your bench synch (all slides open exactly the same amount at a given throttle setting) and you put your gauges on the carbs, are they close to being synched up?  If not then start looking some more for air leaks, or mechanical issues with the engine. . . .  If you can get things into good gauge based adjustment with just a bit of tweaking then . . . .When the the synch goes out of whack, have you pulled the air filters and checked to see if the #1 slide appears to be out of position, ie has it dramatically moved from where you set it during the bench synch?  If so, look to OldSchool's stripped nut or linkage issues.
Logged

Offline Spanner 1

  • Old Timer
  • ******
  • Posts: 4,092
  • CB 750 K0 ( always thought it was a K1!) + CB750K8
Re: The carb with a mind of it's own.
« Reply #3 on: April 05, 2009, 07:28:22 PM »
Think it's air leak still...try grabbing the carb rack left and right, sitting on bike at idle with gauges connected and 'rock' the carbs up and down to help show-up any manifold leak while looking at the vac. gauges for any changes...also #1 valve leak would cause this also.....
Logged
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

nwest4

  • Guest
Re: The carb with a mind of it's own.
« Reply #4 on: April 06, 2009, 06:27:15 PM »
thanks for the replies, will check all of the above and see what shakes out of the tree.  Any other possibilities, I'm all ears.  Thanks again.
Logged
Pages: [1]   Go Up
« previous next »