My bike wont idle, but will run if you hold the revs up.

[tomf]

Hi i have just brought a cheap bike for driving round the farm on but the bike wont hold the revs it will kick over and fire up, but if you dont hold the throttle partually open it will die.

This is a side image of the carb, i have twised the sprung screw in the middle all the way in and all bar 1 thread out and it made no difference to the idle speed...

https://i92.photobucket.com/albums/l34/tomfc/120300030-2_blank_500.jpg

there does appear to be be kind of screws a and both the air filer and engine side of the carb as can be seen in these pictures.

air filter side

https://i92.photobucket.com/albums/l34/tomfc/120300030_blank_500.jpg

engine side

https://i92.photobucket.com/albums/l34/tomfc/120300030-3_blank_500.jpg

I have completely striiped the carb down and everything was imacculate inside, i did still clean everything in the parts washer and blow all the holes through with the air line. THis cleaning process didnt appear to bring up even the finnest spec of dirt.

If anyone has any ideas on why the bike wont idle that would be great, please dont write back saying about cleaning the carb as it really is completely spotlesst, iv not had it off 4 times to try and find something blocking something but there is no dirt in there atall.

[lonie]

well my first thought was the pilot jet but if you say its clean then... have you taken the jets out and cleand them?
it has to be a fueling problem have when you start it do you use the choke?
how much choke do you use try holding the revs up andthen takeing the choke off and see what that does

[tomf]

Thanks for getting back to me.

I have tried the choke in all the positions, it starts alot easier with the choke all the way out but it just wont keep the bike idling.

As for the jets i dont belive i have removed these as im unsure where they are located. i removed the throttle damper part and the float bowl and just thoroughly cleaned everthink visible.

Do you have any idea what the piolet jet looks like or where it would be located?

Sorry if i am asking silly questions, if you havent guessed im new to bikes.

[Bladey]

Yep i agree..gotta be the jets... and if im not mistaken..someone correct me if i am, but there is (in most cases), an idling jet seperate from the main jet and also independently controlled, via thumbwheel or screw/locknut.
____________________
No Bike ...No Life, i can Live without the Wife
Kawasaki ZX6R '01' Red/White <--Summer Days
CBR 600F '98' Black <-- Any goddamn Day

[tomf]

Thanks atleast it looks like it might be fixable.

So does anyone know what the jets look like so i can remove and clean them up?

would it be the bolt and both the air filter side and engine side that come up from the bottom? they can both be seen in the pictures above.

or are they internal?

[mr rip]

I would also guess at it being down to the pilot jet blocked or the mixture screw being turned all the way in

if you look at that last picture you posted the mixture screw is that brass one coming up from underneath, in front of the float bowl,

check that it hasn't been screwed all the way in before you start stripping it any further, as a rule of thumb it should be about 2- 2.5 turns out

if this isn't the problem then whip the float bowl off, the mixture jet will be the smallest of the 2 jets in there, normally closest to the engine side of the carb, & is some times recessed into the body, you will need a thin screwdriver to remove it although you could probably get away with just blowing it out in situ
____________________
never criticise a man until you've walked a mile in his shoes, then when the muck hits the fan you'll be a mile away & you'll have his shoes

[----]

Part of cleaning the carbs is to also remove/clean and blow through the jets.
To get an idea what they look like simply do a search in google images for idle jet.It's just a case of removing the float bowl to get at them.

What condition is the inlet manifold in? A really small split in the intake can cause these symptoms.
____________________
DRZ-400sm

[lonie]

ok its obvios that you havent cleand the jets then so take the carb off and remove the float bowl just as you did before now look in the top of the carb and you will see two bits of brass sticking up the bigger one is your main jet get a flat head screwdrivwer and unscrew it raise it up to the light and you should bne able to see throught the hole itl only be a little pinprick of a hole though then get a can off compressed air and spraigh through it to clear any crap outa it

now the pilot jet is the other brass bit same method remove and clean

then reassemble and viola hopefully a fixed bike

hope this helps got ma fingers crossed for ya mate

lonie

[tomf]

Thanks everyone, really cleared everything up for me, ill hopefully be able to strip the carb down on wednesday. Ill let you know how i get on.

Thank again, Tom

[tomf]

OK a bit of a twist to this.

I went to have a go at sorting the non idling problem today.

I started the bike up and it would run for about 5 minutes (still have to hold the throttle open though) and then the bike just died and wouldnt fire back up.

So i took the plug out to find i couldnt see a spark at the plug, so i tried a new plug and exactly the same, so i checked the wires going to the coil, one was an earth and one was a live.

Im unsure how to test the coil so i put the multi-meter into the end of the ht lead and measured the voltage, i was getting around 12v depending how hard i kicked it over, but this voltage was near enough exactly the same as what was going to the + side of the coil and i thought the coil was supposed to hugely increase the voltage is it now?

any help on this would be great.

[kt]

The voltage on the input side should stay around 12 volts but the output side will be several thousand so the readings you have sound correct.

[tomf]

Thanks so does that sound like the coil is knackard then as im getting the 12v at both imput side and the out put at the end of the ht lead.

[Noxious89123]

Can't see how it would be possible for it to output 12v tbh. And I think if you put it on the HT side of the coil it would likely blow up your multi-meter?
____________________
'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[tomf]

Im not sure how its going it but it is, the coil have one black wire going to it and one green wire, with the ht lead as the output.

black wire shows 12v
green wire sows 0v
HT lead shows 12v

im not sure why im getting these results but i tested these atleast 10 times and got the same results every time...

Anyone got any ideas atall, as i thought surely if the coil failed it wouldnt give any output atall, all i can think of is maybe the internals have broken down somehow and the input is shorting, bypassing the coil somehow to the other side of the coil, but i cant really see how this could work...

Really regretting buying this bike now.

[mr rip]

if it was a two stroke I would be suggesting you check your magneto side crank seal about now, but looking at the choke on that carb it would have to be a four stroke

if you let us know what the bike is, someone here might have a manual for it or could probably tell you the best way to go about testing it
____________________
never criticise a man until you've walked a mile in his shoes, then when the muck hits the fan you'll be a mile away & you'll have his shoes

[tomf]

You are correct the bike is a 4 stroke.

Its a lifan gy125.

[molex]

Maybe read this post also


https://www.bikechatforums.com/viewtopic.php?t=198114&highlight=