Demon 125cc china pitbike, choke question

[vic1616]

hello, i have a 125cc pitbike. its weird cause its runs all ****ty and stalls out when i have the (plastic) choke lever up. but when I have it down, thats when it runs well. I even start it with the choke down cause i figure theirs no use to have it up as it will just end up stalling. I just got the carb cleaned too, as this was a problem before the cleaning. Can anyone explain? Is this normal? heres my bike. It seems to run fine with the choke down, but not up..

 

[timeeh]

More than likely choke down is choke off, some chinas are like that. Nothing to worry about.

 

[vic1616]

yeah, thats what im saying. it runs fine when its down (off) but when i put it up it stalls out and doesnt rev well.

 

[timeeh]

but when i put it up it stalls out and doesnt rev well.

Which is what is meant to happen when your choke is on.

 

[timeeh]

Is this normal?

Yes.
.......

 

[vic1616]

so what is the point of having it on? if people say its better to have it on for it to warm up then take it off, when it doesnt even run when i put it on

 

[timeeh]

so what is the point of having it on? if people say its better to have it on for it to warm up then take it off, when it doesnt even run when i put it on

It is there to help with cold starting, what it essenstialy does is severly reduce the amount of air coming into the carby (such as the name "choke") which in turn makes for a "richer" mixture (more fuel) which helps the engine fire up, however this does not help when running the bike as the air/fuel mix is not correct until the choke is turned off letting more air in and creating a leaner mixture.

Long story short if your bike starts without the choke on, thats great, don't use it. However if you find it wont fire without it on (i.e too cold) then turn it on, fire up the bike, idle for a minute then turn it off and ride. Hope that helps

 

[my67xr]

i cant see the carby too well in your pics, but is it like one of these?
round fuel bowl, lever/butterfly choke on the the air filter side of the carby?

 

[vic1616]

thanks. but what if it wont idle when the choke is on, but is fine when its off. it just dies when its on. How can that be, i notice alot of people have there bike idling fine with choke on mine just bogs out when i hit it up.

 

[vic1616]

im not sure ide have to go look lol why would it make a diff tho

 

[my67xr]

take the air filter off, and have a look inside the carby
with the choke on, the butterfly/flap will be closed, and open/horizontal when the choke is off.

who cleaned the carby for you ?

 

[vic1616]

also, does anyone know the make of my bike? i baught nit off a friend i know its a 125cc but dont know what kind.

 

[my67xr]

we need to know what the carby is, or looks like to help you out

 

[vic1616]

a mechanic who works with pitbikes, he did a rear wheel allignment and also cleaned the carb

 

[timeeh]

Possible your not running the correct pilot jet, or it could be just a problem with the carb, nothing unusual with china carbs, lots of people have lots of problems with them. And if your bike is idling with the choke off, then why would you turn it on? Just leave it off.

 

[my67xr]

we need to know what the carby is, or looks like to help you out


the bike looks like an earlier? model of this Demon DXR125

http://www.demonxracing.com/dxr125.html

 

[my67xr]

as timeeh mentioned,
it does sound like the pilot jet possibly is blocked?
with the fuel bowl off, you will see 2 brass jets, on in the centre of the carby, the other smaller one slightly forward (towards the intake manifold end)
if you unscrew this jet and remove it, it has some tiny holes on the tube/extension of it, these need to be clear and see through.
they are easy to miss if you aren't looking for them.
also where this jet screws into in the bottom of the carby, there is a port that goes through to the main bore of the carby.
if this is blocked a little bit or completely blocked it will make the bike hard to start, and also it wont rev freely/clean, just bog a lot, and sound flat.

 

[vic1616]

i dont think, i think those stickers dont have anything to do with the pitbike company demon, cause demons use a distinct engine that has the logo that mine doesnt have

 

[vic1616]

and thanks, the bike seems to run fine with the choke down, so i dont see any use for having it up really, unless i want it to die out on me after a few seconds.

 

[vic1616]

is it fine if i start the bike with the choke down and just ride with it down once its warm?