when i push in the choke the bike stops, have cleaned the jets, how do i adjust the mixture, is it screwed al the way in to make it richer or leaner.

this is my sons first bike and trying to sort it out for him, it will run ok on choke, have cleaned out the fuel tank and clean petrol

any help will be really appreciated and grateful
thanks

gary

gary stuart, August 2010

yes without a doubt its a fuel stavation problem so the main jet must be blocked or the slide needle may not be at the right level or the float height may not be right.taking the air filter out will make it worse and its no good for it anyway,try this...take the part at the top of the carb off where the cable goes into it it will just unscrew,then lift the slide out of the carb and then push the cable down and out of the slot that it sits in so you just have a slide in your hand then pull the small clip out that holds the needle in in the centre of the slide and take the needle out from the middle of the slide then look at the grooves on the slide and notice the position of the circlip it should be in the middle if it is then move it to groove nearest the pointed end of the needle an if its at the groove nearest the blunt end of the needle then move it to the middle or the neareset to the pointed end.see how it goes and let me know

adam bike doctor, September 2010

thanks so much, i did indeed mess around with the mixture screw and managed to get it ticking over with the choke completely off.

its a single carb

however when i try to increase the revs it cuts out, no matter how i mess around with the screw it wont play ball.

tried taking out the air filter still no joy.

as you say if i need new jets or a complete carb would you know of where i may be able to get one please.

i cannot thank you enough for taking the time to reply to my question, really appreciate it.



hopefully i may get him either a new carb or jets,
thanks again

gary

gary stuart, August 2010

ok the mixture screw/s on these are set 1.5 turns out from being all the way in.if the bike still only rns on choke then the pilot jets are blocked up or narrowed enough to cause lean running or possibly there is an internal tract in the carb that has blocked up and then the carb/s will need to ultrasonically cleaned.p.s i cant remeber if the cm125 uses a twin carb or a single carb to a split inlet manifold i know its basically a cb125tdc engine though.

adam bike doctor, August 2010