Topic: Always Need to mess with the choke To Run Good

[Dunstall_74]

CB750, 4-1 header, K&N Pods, 125 Main, 40 idle, dyna-s ignition ,Dyna 5 ohm coils.  I cleaned the carbs and made sure jets were clear.  I ran some gas through it, then cleaned the petcock fuel screen.  Took the bike out the next week w/fresh tank of super. The bike ran like crap.  It had erratic idle, and would want to die on take off unless I just revved the piss out of it and rode the clutch a little.  I found that I could get it to straighten out from time to time when I messed with the choke.  When I would find the sweet spot on the choke the bike would just come to life and take off like a bat out of hell.  It seemed that about 2/3rds closed on the choke was optimum when at cruising speed.  Less than cruising speed, it was near impossible to find that happy medium.

I am at my wits end.   I have yet to completely rebuild the carbs, although I have replaced the main jets and float bowl needles and seats.  I just ordered Honda factory rebuild kits for all four carbs, which I hope fixes the problem.  Other than that and replacing the Intake boots with fresh new rubber, not sure where to look.

[750goes]

Your Jets may be clear but the complete idle circuit throughout the carb body may be plugged or have junk in it..
also the emulsion tube could be blocked up..

sounds like having to use the choke 2/3rd's on it's starving for fuel..
check your plugs for condition, and have they been synched, and are all your manifold rubbers intact and firm ?

is this just a recent condition or is this the result of you cleaning the carbs ??

[gerhed]

I thought 3 ohm coils were recommended for Dyna-S ingnition ?
I realize that's probably not causing the current problem, though.

[kghost]

Jets may be clear but the internals aint.

Dirty carbs

[TwoTired]

I cleaned the carbs and made sure jets were clear.  I ran some gas through it, then cleaned the petcock fuel screen.  Took the bike out the next week w/fresh tank of super. The bike ran like crap.

Procedure error.  Clean the fuel supply BEFORE cleaning the carbs.  Feed clean carbs dirty fuel and you don't have clean carbs anymore.
You don't need super.

Also, pull the plugs to see of there is carbon on the center insulator.  Abrasive blast, or replace, if so.

Are the pods oiled?

What setting did you use for the air bleeds on the carbs?

Where did you set the throttle jet needles?

With the mods you made, you can't expect the slow circuit and throttle valve setting to remain at stock settings.   Some assembly required. 

Cheers,

[Dunstall_74]

I have yet to do a plug chop, but the filters are oiled, the air screws are a turn and a half out, and I am not really sure where the clip is on the throttle needle.  I will soon find out as I am going to rebuild the carbs.  I have avoided the clip position as I hate syncing the carbs.  It would be nice if you could change the clip position without screwing up your carb sync.  I will get back as I find out more