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idling problem

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idling problem

Hi guys

 I seem to have a problem with my honda cbf250. When i start the bike from cold i turn the choke on which usually increases the revs to warm up , though recently it doesn't and I have to hold the throttle to keep it running.It doesn't always stay idling when fully warmed up either or restarting when warm it just cuts out.

I've changed the spark plug but funny enough it didn't solve the problem (though did notice a slight performance increase), the colour of the previous plug was a dry biscuity brown (digestive).Also checked the air filter and that was fine (very light colour) ,also checked the battery although it did improve briefly when the battery had just been charged but not for long.There is an throttle cable stop screw on the side of the carb it works to help the idling initially when warming up but i have to adjust it again when its warm as its revving too high(normal revs 1400 rpm). I'm wondering if its an electrical or a choke problem??

anyone have any ideas??

If putting the choke on or off doesn't change the engine running then it sounds like there's a carb or fuel problem.Most of the symptoms suggest the choke's sticking on (except for the dry, brown colour of the spark plugs, and the fact it doesn't idle fast while warming up anymore), so it's probably worth checking that as it won't take long.Another check you might find helpful is to check the fuel height. Depending on the carbs you should be able to do this with them still on the bike by connecting a U-bend of clear PVC tube (from B&Q etc) to the float bowl drains on the carbs, your Haynes manual might tell you what the level should be, but as a rough guide the fuel should be roughly level with the float bowl gasket joint. If it's very different, or there's a big difference from one carb to the other then it's worth further investigation. Assuming the fuel height's correct, then having to adjust the throttle further open to idle, and then dropping it when it's warm suggests that either some of the fuel jets or the air bypass jets are blocked. These are jets that allow air thru' the carbs while the throttle is closed, and pick up a bit of fuel on the way. The inlets to the air jets are usually a couple of small holes at the bottom of the bell-mouth where the carb meets the airbox. It can be worth blowing these thru' with some compressed air (if you're desperate you can rig an air line off a car spare wheel). This is best done with the float bowl off as that sort of pressure over a large area could cause damage.If the bike's got normal power most of the time then it's unlikely to be fuel starvation, but debris or rust / crud brought down from the tank could've clogged the jets or the float bowl, so if you find the carbs are a bit full of crap, it's worth cleaning out the fuel lines, tank, and fuel tap (be careful when you take it off). It's also worth fitted an in-line fuel filter. Most local bike shops (not snotty nosed main dealers) will sell them - just make sure you get the right size for your fuel pipes.I'm bound to have forgotten loads, and missed something obvious, but maybe consider some of these in the mean time.

thanks for the tips tappy!, will check them out

Thanks for the useful

Thanks for the useful information! I helped your advice!

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