Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: Sam Johnson on September 18, 2007, 04:18:51 PM

Title: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Sam Johnson on September 18, 2007, 04:18:51 PM

Hi,

Any ideas please?
There is slack in the cables, the throttle stop is screwed right away from the
stopper. The bike starts and runs fine but will not shut down to below 2.5 Thousand revs.

Help (CB750K2-standard trim)

Sam

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: daveh on September 18, 2007, 05:10:06 PM

I guess if none of the throttle slides are sticking open. Then check the ATD is retarding and has not stuck in the advance position.
best of luck
Daveh

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Spitfire on September 18, 2007, 06:57:54 PM

Ok, what condition is the bike in, has it been sitting for a long time, has the problem suddenly appeared, has the bike been worked on recently ? Do you have a manual ?

Are the throttle cables in good condition, and sdjusted correctly, 3-4 mm at the adjuster ot the carbs end.
Are there any leaks on the carb rubbers between the carbs and the cylinder head, spraying WD40 on these will speed up the tickover if there are any leaks..
Try pressing down on the tops of the carbs.
Is the throttle action smooth indicating that the slides are OK.
Take the tank off and see if anything is mechanically stopping the carb slides dropping.
There is another adjuster on the carb linkage just below the "pull" cable this is eccentric and there should be a 2-3 mm gap present between it and the throttle lever, this could hold the slides open. (it's called Overcross stop adjustemnt on the manual) When your cables are adjusted properly by firmly closing the throttle from the tick over position it will slow the tickover.
Look at the slide stem on top of the carb you should only see about 1 - 2 mm of shiny stem.
What are the pilot air screw set on, screw them all the way in (to contact only, don't force them) then screw them out 1 1/4 turns

Cheers

Den

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Dave M on September 19, 2007, 07:46:29 AM

Air leak or mixture screw sounds good especially if the bike's been stood with fuel in the carbs for a while.

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Sam Johnson on September 21, 2007, 12:14:49 PM

Thanks Gents for the info.

I think its down to the carbs. they appear to be way out. The bike starts fine on choke and rides fine.

There is slack in the cables so it must be that the slide rods are to open?

I have also found that the number 2 plug is crossthreaded!!!.

Kind regards
Sam

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Sam Johnson on October 02, 2007, 06:31:41 PM

SORTED,

Carbs set and tuned and the number 2 plug hole re-tapped. Bike runs fine now and even shuts down!!!

Looking for a new seat and any ideas of where to get the wheels rebuilt with rims and spokes?

Thanks for the ideas, great bunch of blokes.

Sam

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: SteveD CB500K0 on October 02, 2007, 07:41:33 PM

There are wheel builders around.

Where are you?  (complete "location" in your profile)

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Dave M on October 02, 2007, 08:42:55 PM

I've been looking around for wheel builders too and they're a bit thin on the ground however I have found a place in Liverpool who'll rebuild my rear wheel using a new rim and spokes on my own hub.

Shoud cost around

Title: Re: Throttle won't shut down to below 2.5 thousand RPM?
Post by: Spitfire on October 14, 2007, 04:46:16 PM

Hi  Sam, sent you a PM regarding wheel builders.

Cheers

Den