When starting the bike it runs at 4-5000 RPM

[Bradleyrayner]

Hi there i have a sinnis apache 125 58 plate. When i start it from cold within 30 seconds the bike starts to run at 4-5000 rpm. I was wondering if anyone could help me with this problem. I have tried playing with the idle screw but this does not make a change. I need to get it fixed before it starts to break my camshaft and cylinder head.

Thank You

[Krasi]

Is that a 2 or 4 stroke engine?

If it's 4 stroke, the best would be to take off the carburetor to clean it and check for the choke sticking or something.

[Bradleyrayner]

Hi there mate it is a 4 stroke engine and i was thinking about taking off the carb and cleaning it. Also when i start the bike, the choke is up which i am presuming is on. I leave the bike to warm up and when the bike is hot enough i turn the choke off and it dies. No matter how hot the engine gets the choke doesn't want to turn off. Can you please help me with that.

[Krasi]

Do you have an air filter? Clean and lubed? Check for air leaks too (e.g. by spraying starting fluid around the carb while the engine is running).

It sounds, like your pilot jet could be clogged. Before taking the carb apart to clean it, try to tap it few times with the handle of a screwdriver or something. Hopefully this will make the clog drop back into the bowl and free the pilot jet.

[Bradleyrayner]

Hi there sorry its been a while but that still has not fixed it. Have you got any other ideas?

[Krasi]

Well, high rpms mean a lot of fuel and/or a lot of air. So, if you don't have an air leak, the carb is not clogged or missing jets, and your throttle is not stuck, I think you can apply for a Nobel prize as you've invented "perpetum mobile"

[MJH]

You may have a couple things going on, I suspect the throttle cable is not adjusted correctly and you have the choke position backwards.


Check the limit on the throttle cable, if the idle screw is doing nothing that makes me think you are not moving the arm with it or in other words your beyond the range of the idle adjustment screw already at 4-5K rpm.
When you adjust the screw it should either touch and move the arm or completely loose contact with it, the former being turning up the idle the later being lowest setting for the idle.


The throttle cable moves the arm with each twist, when the throttle is released the arm should drop to the limit of the arms range of movement, the idle screw raises it off the end limit.


When the choke is applied to a warm engine you are cutting off the air supply it will stall. You are effectively likely starting the bike with the throttle above the idle and with the choke off just like giving it more gas


Check the cable make sure it is at its limit and not too tight , turn the throttle and check its range of movement at the arm, were it attaches to the carburetor, with a twist it moves, with release it drops to the limit. The idle screw is next to the arm it moves it off the limit when turned.