VL 125 idle problem

[bikeradam]

Hi everyone, first time on the forums so i'll introduce myself first. I'm 17, been riding for just under a year, had an Aprilia rs50 once i passed my CBT, then moved onto a vl125 last summer.:thumbu:

Now heres the problem. Once the engine is warmed up and left at idle speed with the choke off, the revs will rise quite high, then fall really low, really quickly. This repeats a couple of times until they fall enough to cut the engine out.

Any throttle applied when the revs are dropping doesn't make any difference.

Any help will be much appreciated.

Cheers

[John Hopkins]

Hi bikeradam, welcome to the forum.

Fill in the UserCP up there on the left so that we know something about you.

Are you male 'adam' female or poof..do you like sheep,

take the bike for a run with whats left of the petrol in the tank then half fill it with fresh petrol and bung a swage of carb cleaner in the tank and run it again..do that before you start thinking of other stuff you might get lucky.

John.

[bikeradam]

hi john

i've updated my details, i'm a lad, and no i dont like sheep :thumbd:

ive been running the bike with the carb cleaner in the tank for the past couple of days, with no difference at all. :(

its really starting to annoy me now :mad:

cheers

[John Hopkins]

OK Adam,

From the sound of it you have carb trouble.

you haven't given any history yet so this is the time to do it.

How old is the bike.

How long have you had it.

has it been standing in the rain or under a tarp for an extended period.

have you or anybody else done any recent work on it.

how long have you been aware of the problem.

[Grav]

Welcome to the forum, Adam. :)

It sounds like it's running on one cylinder and the revs rise when it fires on both and falls off again as it drops back to one cylinder again.

Check the simple stuff first, Adam. Check the spark plugs are clean and correctly gapped and make sure they are giving a good spark. As you take them out, check the colour of the electrode as this will tell you which cylinder is running intermittently. The following link will give you advice on what's happening and why.

http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

Once you're happy it's sparking properly take a look at your throttle and choke cables. Make sure they are moving smoothly as a sticking cable can also give you the problem you described.


My Mrs had a VL 125 and it's a cracking little bike to ride. :)

[John Hopkins]

Easy way to check if it is on one cylinder, one exhaust pipe will be hot and the other cold..

John.

[johnr]

Easy way to check if it is on one cylinder, one exhaust pipe will be hot and the other cold..

John.

tricky on the vl, the silencers are linked together and the downpipes are tiny sleeved pipes so you can run it for 5 minutes and the downpipes will still be cold!

having similar probs with my eldest daughters boyfriends vl125lc at the mo. firstly, get yerself somewhere dry to work,

ok, seat off first, then tank off, chromed plastic airbox pods off too.
right, you need to check some stuff first, the carb has a push/pull cable. if you dont have the return cable, the carb might not shut fully when you shut off. on a motor as small as the vl it doesnt need much to get it revving up and down.
assuming its got both cables, take the carb off, it means removing the rubber elbow to the air box, the cables and choke cable and a couple of wires that connect to a carb heater to prevent carb icing.
carefully strip the carb and soak everything overnight in carb cleaner in a coffee jar, all the jets can be soaked in vinegar to clean them up!
put it all back as you found it, gently wind in the air screw as far as it will go, then wind it back out 1 1/2 turns.
now before you go further take off the ht caps remove the plugs and clean them, check that the coils are tight on their mounts. unscrew the ht leads from the coils, cut a half inch off the end of the leads and then screw them back in nice and tight, they tend to work loose after a while and can missfire which is more apparent at tickover cos it makes it lumpy as hell.
then, try it. i cant make any guarantees, but this has so far worked for us, and it eliminates a few of the variables.
its also worth checking that the bike is charging ok, low voltage makes the bike cutout as the cdi cant cope with under 12v.

[Grav]

One thing I did find on the wife's VL125 was the needle jet assembly had a nasty habit of unseating itself from it's guide pin and swivelling round. Once corrected it ran without any more hassles. The assembly i'm on about is the bit where the long needle on the end of the throttle slider goes into. There's a small guide pin the assembly locates into and it has been known to spin round. There is a small hole in the assembly that must be pointing in the right direction or the vacuum generated by the movement of the pistons will not be able to suck the right amount of fuel into the cylinders. It's a simple fix but does require removing the carb to get at it.

I have some parts diagrams on pdf. If anyone wants them PM me your e-mail address and I will send them. :)

[johnr]

I have some parts diagrams on pdf. If anyone wants them PM me your e-mail address and I will send them. :)

you got my email grav?

[Grav]

No John, i haven't.

[John Hopkins]

tricky on the vl, the silencers are linked together and the downpipes are tiny sleeved pipes so you can run it for 5 minutes and the downpipes will still be cold!

.

Feel the pots..

John.

[jcb]

sounds like you have an air leak in carbs to airbox area or possibly the inlet manifolds.
or a plug isnt seated right..
or water in fuel tank...
or...:unsure:

[johnr]

vl is single carb.

[jcb]

never heard a a vl125 heh.
ill go with water in fuel or blocked fuel filter mebbe but with no idea of its history/condition etc etc then could be anything.:rolleyes:

[John Hopkins]

Y'know Adam has only posted twice and may never return to this forum, he is only 17 and probably hasn't even got a licence yet so we shouldn't expect too much from him in the way of repair ability..

So Adam..if you are still there..

Your previous bike was a two stroke which used petrol and oil mixed..this one is a four stroke that uses straight petrol..do you know that if you use the remains of a tank of two stroke fuel in the VL125 instead of straight petrol the engine will run uneven and cut out..

John.

[johnr]

Y'know Adam has only posted twice and may never return to this forum, he is only 17 and probably hasn't even got a licence yet so we shouldn't expect too much from him in the way of repair ability..

So Adam..if you are still there..

Your previous bike was a two stroke which used petrol and oil mixed..this one is a four stroke that uses straight petrol..do you know that if you use the remains of a tank of two stroke fuel in the VL125 instead of straight petrol the engine will run uneven and cut out..

John.

aprillia 50 was autolube, you give your age away, its been at least 20 years since anyone sold a bike that ran on premix!! my last premix bike was the bantam that lives in the corner of my lounge!

[John Hopkins]

aprillia 50 was autolube, you give your age away, its been at least 20 years since anyone sold a bike that ran on premix!! my last premix bike was the bantam that lives in the corner of my lounge!

Yes I have heard about these new fangled ideas..next they will start fitting electric starters and disk brakes..

John.

[bikeradam]

Thanks for all your replies.
John I definetly havent put 2stroke in it! Ive had the bike for about 6 months, its a 2000 model and use it for college most days except when its snowing. Its always kept in the garage on a night, and only kept outside when I'm at college.

Its been running great up until the cold weather came in. I did all the easy things at the weekend, checked the plugs and chopped a bit off leads, I took the bottom of the carb and squirted carb cleaner through all the jets I could see. Still no better. Will have more time this weekend so going to do proper carb strip down.

It does sound like its going onto one cylinder but as its only got one carb feeding both cylinders will it be the carb? Could it be the fuel pump or would a faulty pump just stop it running altogether?

Cheers
Adam

[John Hopkins]

Its been running great up until the cold weather came in. I did all the easy things at the weekend, checked the plugs and chopped a bit off leads, I took the bottom of the carb and squirted carb cleaner through all the jets I could see. Still no better. Will have more time this weekend so going to do proper carb strip down.

It does sound like its going onto one cylinder but as its only got one carb feeding both cylinders will it be the carb? Could it be the fuel pump or would a faulty pump just stop it running altogether?

Cheers
Adam

It could still be a dirty carb but it is less likely..did you replace the sparkplugs with new ones or did you just clean the old ones, plugs can look good but break down when used so new ones are cheap..if that has been done. don't just cut bits off replace the HT leads with new ones they can also break down in cold weather and they are cheap enough to replace.

Easy and cheap things first..

John.

[Mistress Maker]

Dont know these bikes.....however as john says , look to the lectricals.

Makes sure the coils are properly mounted, check the wiring from the coil, the low tension side, a fault here espescially an intemittent one will be hard to find but probably something simple. bad connection, etc, or an earth fault.

A method I once had success with on HT leads breaking down was, run the bike till its warm etc, then put it in the garage with lights off at night, so there is no natural light. start it and if leads are breaking down and making contatc anywhere else you may see a small spark. Don run it more thqan a couple of seconds then re open the door. dont want to gas your self.

also try the bike open with the petrol cap open see if it still does it, it might not be sucking enough fuel through and pulling a vacuum in the tank. simple to check, may be a complete waste of time, but worth checking.