vespa lx 50 running too fast after establish vacuum pipe!!

[hdaveharris]

ok this is my first post and I am not a mechanic so please be gentle!!! Smile

My son has a 2006 vespa LX50.
It would not start, battery was good and strong spark at the plug.
Tried few times and spark plug was dry, so thought fuel delivery problem. Took fuel line off carb and no fuel delivery, when turning over. Knowing this has a vacuum operated fuel tap. I also removed vacuum pipe from carb and when sucked on it to re-establish vacuum, fuel flowed easily.

Re-connected fuel pipe with fuel flowing, then re-connected vacuum pipe to carb.

Started her up and boom fired straight up!! SO whats the problem? Well whilst she started up, it is running way to fast and the back wheel spinning likes its flat out!! The throttle isn't sticking as it still turns and the engine revs even more!!!

Its running so fast its moving off across the garage floor whilst on stand!!

Expect may get a few replies to this bit (but be nice!! lol) - Did I suck too hard causing too much fuel to be delivered? or is something else amiss.

Really appreciate help as want to get him back on road for college.
Alternatively need to get it recovered to nearest scooter mechanic and they charge a fortune for collecting!

Thanks for your time

[Teflon-Mike]

Pull in the back brake to lock the transmission.
If it stalls then the engine revs are too high and centrifugal clutch permanently engaged or is stuck.
Has he been muggering around with it trying to make it go faster? (16 year olds have this myth that messing with the variator makes their peds uber much faster)
The throttle stop may need adjusting, or the throttle is jammed some-how? (again fiddle fingers to make it faster could be a culpret)
Has he fallen off it? That could be another cause, if a cable has been snagged or similar.
Is the choke on? Stuck on?
If its racing on the stand, could just be flooded, from non-starting, and may clear, if you hold the back brake in and put it under a little load while it burns off excess fuel.
If not, then may need to look for deeper cause; possibly a stuck float in the carb or undoing fiddle-finger-fastering.
____________________
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[hdaveharris]

Teflon-Mike - thanks for the reply I will have a go again in the morning and will try the back brake trick!

In fairness to him I doubt he has been fiddling as he wouldn't know where to start! It already goes to fast for my liking as must have been de-restricted before we bought it as it goes faster than the standard 28mph!!

Does this have an auto choke?

Hoping its flooded from when I re-connected fuel pipe with fuel flowing, but ran it for a few minutes in turbo nutter mode and didn't settle down...
Fallen off it - now that's a possibility!!! wouldn't be the first time!!!

thanks again and will keep playing...prefer my GSXR1000 as i just take that to the garage!!!

[hdaveharris]

Ok had a go this morning just to wake the lazy tykes and get them outta bed!!

Right so If I start it up holding the bake brake on and keeping it on, it starts fine and the back wheel holds with engine running at reasonable revs.

If I apply throttle it increases and decreases revs as you would expect.

Soon as let the back brake off, it builds momentum and reverts back to racing with the back wheel spinning as if at top speed. If I then apply brake whilst it stops back wheel spinning it sounds like something is about to give!!! and the revs maintain very high.

Any ideas greatly appreciated, if not think going to have to try and ride it myself to workshop!!! 17 stone on an LX50 ain't gonna be pretty!!!

[_Iain_]

[hdaveharris]

ok have cracked it.

Having gone back through Teflons advice I thought I would look up a diagram of the carb and then check cables, auto choke etc..

Clearly as from the photo's below when re-attaching vacuum pipe to carb I have moved the throttle cable to one side to allow access, this has obviously kinked cable causing it to over rev..

Soon as moved it back into a straight alignment, voila!!!

so sometimes the simple things work!!!

Thanks for the help Teflon.

[_Iain_]

Good to hear you got it sorted
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[hdaveharris]

thanks _Iain_... he will be relieved as wont be walking three miles down country lanes in the rain to train station!!! lol

This forum really helps to have someone to get ideas off.. I can work through things but sometimes need a bit of a steer in the right direction..

Keep up the good work..

Cheers