Topic: Throttle sticks/rises

[slkern]

Hi, I'm having trouble with my throttle.  I own a CB750 K2 and when I first kickstart the bike, it idles nicely but after I ride a little while I noticed my throttle tends to hang around 3,000 RPM.  Sometimes when I'm stopped, it will even rise on its own.  I can cause the RPMs to slowly drop if I force the throttle forward.  Now I'm relatively new to bikes and was wondering if any of you SOHC4 maestros could help me diagnose the issue?

Thanks,
--Samuel K.

P.s.  Could this possibly be related to my throttle stop/idle screw?  A friend of mine recently disassembled, cleaned, and synced the carbs but accidentally snapped the throttle stop/idle screw, which I replaced with a temporary screw.

[ekpent]

What I notice on the early 750's due to the fact that do not have a fast idle built into the choke or carbs when starting cold is that the idle is generally lower than normal and as they warm up the idle may become higher and more smooth.I cannot usually just walk away and let mine idle when its colds without manually increasing it with the idle adjuster knob,then backing it back off when warm to my desired idle.
  That being said if you can force your throttle closed more to decrease its idle or drop the slides more the problem may be in your push pull cable adjstuments or routing.
 

[dusterdude]

True,thats the way mine is,have to let it get good and warm before setting idle speed

[slkern]

All right, I’ll try warming up the bike before adjusting the idle.  I believe my push/pull cables are properly adjusted but I’ll check them as well.  Thanks for the tips.

[dusterdude]

Hope it works

[slkern]

Hey guys, I adjusted the idle screw once the bike warmed and it worked!  However, I noticed after I fixed the idle, my left exhaust would pop on deceleration.  Any ideas on that?  Is it related to the idle screw or something completely different?

[ekpent]

Could be an exhaust valve out of adjustment,cylinder running a little lean or a slight leak of somekind.Do not think it would be related to the idle adjuustment. How stock is your set up for intake exhaust etc.?

[slkern]

I have a 4-into-2 exhaust with Uni pod filters instead of a stock 4-into-4 with a single air filter.

[flybox1]

popping on decel means you are lean (not to mention the fact you have a filter system that will lean you out, too)
you will need to adjust all four of your fuel mixture screws slightly richer. 
1/8 turn adjustment.  ride.  adjust more if needed.

[slkern]

Thank you!  I'll do that now.  But before I do, I should probably know what screw to turn.  Haha.  I attached a picture of my carbs, can you identify the fuel mixture screw?  Also, do you turn the screws out to richen the mixture or vice versa?

[flybox1]

note is position.  its between the carb slide and air intake, so it meters AIR.. out is more air(leaner) in is less air (richer)

[slkern]

Awesome.  Thanks so much.  I'll get to it and report back here in time.

[Psychonaut]

Popping on decel does not necessarily mean you are lean. Low back pressure exhaust will pop on decel. 

[flybox1]

Low back pressure exhaust will pop on decel.

exactly.  thats what he's talkin' bout!    
slkern, 1/8 turn in to richen it and you should be pretty close.
you can check your plug color to verify (before and after)

[slkern]

Well, I did as you said and that seemed to work!  There's no longer popping on deceleration.  Thank you flybox1 and to everyone else, I really appreciate it.  Now it's on to the next thing.