Hey guys, so I've just had my 2010 yamaha xt 125 rejetted so that it would idle without cutting out. It worked perfect for a couple of days, starting off of the button first time. Now it's been almost a week and the bike is dying again whilst idling, with any amount of choke. So is this thr carb yet again? Thanks in advance

Sounds like you have got crap in your tank,try cleaning the carb and installing a in line fuel filter.

Thanks dt50, the carb was spotless but I'll do it again. Fuel filter a cheap job?

Yep under 10 bucks cut the line and install with the arrow going to the carb,just get one the same size as your fuel line

You could also clean the tank with vinager and some screws,nuts what ever,just put them in and give it a realy good shaking, remove the fuel tap first though dont want to break the res/on pipe.If the tank is realy rusty then you might want to seal it with Kreem tank sealer.

The tank is a hard plastic so if there is crap in there it'll be from the cap, so maybe this isn't the problem

Why did you rejet for idle! It works off a different part of the carb.

Check the air screw is set too the correct amount of turns and then the tickover knob, after that look for air leaks also make sure the spark plug is tight. That should keep you going for a while.

PS. If you open the choke on a hot engine it should cut out its only for cold starting.

Sorry for the misunderstanding Preload. My girlfriends Dad did it, he's great with bikes, so he jetted the bike in whichever way so it ran well, which it did, for a while. The choke starts the bike well at 1/4 in and then it goes straight off as I've heard that's what's best. I'll check the air screw and tickover. Thanks

I see Scott it was a separate issue.

, so he jetted the bike in whichever way so it ran well,

So" that means he swapped jets ? [ jetted] or did he remove and clean the standard jets?, sounds like the pilot jet is blocked,

Hi blackhat, I'm not a mechanic nor am I great with the terminology aha. As far as I'm aware he removed and cleaned everything on the carb, including the jets, and then rebuilt it. So he kept the original jets. Now it's been a few weeks the bike only cuts out when started some of the time, and other times runs well. Maybe it's just this cold weather?

By cuts out do you mean it just stalls and then you can restart it?

I see you said 1/4 choke and then off immeaditaly after starting,no bike will run cold well you have to give it a few minutes to warm up before turning the choke off fully.

How many bikes have you owned?

Yeah the bike can be restarted straight away. That's the thing dt50, when the bike is cold started with or without choke it will idle quite low at around 900 rpm and then die after around 5 seconds. This will happen only when very cold for the first 3 or 4 times of starting the bike. Secodondly at this same point of cutting out, if I give the bike throttle it will die also. So should this just be a carb clean again?

This is my first ever bike, I'm 19 and I've only just been able to afford one you see.

Also just to add, the choke does work.

Try starting the bike with choke and let it run with the choke until the revs start to pick up on thier own.This sould only take 1 minute or so dont give any throttle untill then.Once the revs pick up give it a bit of throttle and turn the choke of gradualy.

The other thing you can do is to turn the idle up to about 1200 with the bike warmed up,to do this you just need to turn the thumb screw on the side of the carb clock wise.As Airhead said it could just be the idle is set too low or the pilot needs richining for the colder weather.

Try this and report back,it's possible you have a small air leak cold but we can cover that later.

Ok I'll give that a go in the morning when I'll be riding it to work. Right now the bike idles at 1100 when warm so 1200 won't hurt to try. My carb doesn't have a thumb screw so it take a bit of messing to get to the screw, but it's easily done. I have checked around the carb for an air leak with wd40 and didn't find anything. Thanks for your time guys, it means a lot with me just starting out with my first bike.

The bigger picture is to finish the years insurance on this bike, and in that time get to grips with the mechanical side of it, and then do my A2 test and get a 250.

Just turned the idle up slightly like you said. The thing with the choke is, and I've heard this is the case with many bikes, is that there's a 'sweet spot'. Under that isn't enough and over that is too much. So sometimes if I don't go straight to the kick start after trying the button once or twice, to save battery, then the bike will start off of the button and won't cut out.

You may have just answered your problems,if your battery is weak then cold starts will be poor.

You should be able to crank the motor over for 1 min without the battery droping,to a point it cant turn the motor ...is the case the battery falls off quickly?

No the battery is almost full and was new two months ago. One thing I have noticed though, I'm not sure if the bike is supposed to be like this or has an electrical fault, but off the button the bike will only spark twice and then not again until I repress the button.

Are you holding the button or just pressing it and releasing it?

Haynes advises idle speed should be between 1650 &1850. Mines is usually between 1600 &1700. My bike usually takes a minute or 2 to warm up. Are you holding the start button in until it starts or just pressing and releasing?