The choke on my bike works ok but springs off when I release the lever. It was like that when I bought it about a month ago and I have been looking for some way to make the control lever lock without success. Finally today I adjusted the clutch lever handlebar mounting tight against it which has provided enough friction to stop it slipping  for now.  Could something be broken in the choke lever control or am I missing something really simple?
Any advice appreciated.

Possibly someone replaced the spring on the assembly by the carb with one that is too strong?  Not sure how that would happen as I think it is part of the cable assembly.  Maybe the cable is routed incorrectly and there is too much tension on it.  Do you have stock handlebars?

Look under the left hand control. Is there an open square slot? A friction thingy and spring go there, held in by a small metal clip. That provides friction so the choke lever stays in place.

what addy said ...

the friction thingy looks like a black single stud square of lego .. with a angled/sloped end where a lego stud normally is

the spring goes up inside of that .. the little clip bit screws over the spring...

i normally forget the spring and stud thing are in there when i undo the left control.. then spend a minute swearing and looking around the floor for there the 'little bugger' has bounced off to this time 

I followed your directions and found the square hole----- but no friction thingy  no spring-- nada. So I spent a happy hour making my own crude version using a small bolt, spring and a hard rubber washer ground to a square shape. I locked 'em in with a self tapping screw and an extended sprung washer. Works a treat. Cable and routing are ok and my bike is Euro spec. with clip-on bars.
Many thanks for pointing me in the right direction   

Quote from: adidasguy on October 28, 2013, 09:53:45 PM
Look under the left hand control. Is there an open square slot? A friction thingy and spring go there, held in by a small metal clip. That provides friction so the choke lever stays in place.

Oh yeah, I forgot about that.  I replaced my choke cable when I first bought the bike as it was broken inside the sheathing.  That's been 10 years ago at least.