idles rough/dies - idles better when fuel vent vacuum line is off

[HeyScooterGuys]

i'm having an issue with rough idle and dying out.  upon removing the seat bucket I noticed the vacuum line coming from the fuel vent was unattached at the "Y" connector near the intake on the RIGHT side.  When attached it won't idle at all.  Idle screw is all the way in to get it to barely idle as well.

It seems to idle with that line disconnected which results in vacuum leak.  I would think vacuum leak would kill the engine but the opposite is happening - runs better with vacuum leak, stalls with hose hooked up. 

also, on the LEFT side of the bike under the seat bucket, i found a two-pronged electrical connector not attached to anything.  I've looked all around and can't find anything for it to plug into.

any help would be greatly appreciated, thanks!
 

[Iahawk]

I don't have any answers for you but maybe posting some pictures will help get some replies?

[CROSSBOLT]

Idle screws on most carburetors control air to the idle circuit so all the way in means the air to the idle circuit is OFF. Try backing it out 2 1/4 turns, hook up vacuum  line and see what happens.

Karl

[big blue]

I don't know if you have a service manual for the scoot but here is a link to one.http://www.49ccscoot.com/manuals/Kymco_People_S_50-200_Service_Manual.pdf

[Redk]

It is nice when you can remove a seat bucket and tinker on engine components!
If any adjustment screw is All the Way in, it would indicate a problem elsewhere.
Congrats! You found it !

The un-attached connector may also be contributing. Components are generally well engineered, and wire lengths definitively appropriate for their function.  From age, it has most likely taken a set, to approximately where it should be attached, and the length will confirm that.

Considering your description, it could be going to an electronically controlled enrichener circuit.
redk

[big blue]

Do you know if the auto-bystarter (choke) is connected or even there? That electrical plug could be the connection for it. I think a carburetor tear-down may be in order and there are many YouTube vids to assist you with the process.

[HeyScooterGuys]

thanks for the responses fellas!  i've seen pics others have posted and i've seen the same vacuum line unattached. 

the carb was disassembled, soaked for a week, re-assembled and re-installed.   still having trouble getting it to run to my standards as the open vacuum port still has me scratching my head.   I found a link on resetting the tps sensor* and that has seemed to help get the idle a bit more acceptable. 

still, as soon as i cover the open vacuum port it will die immediately.  this is very strange as i've never seen this behavior on any other scooter.  In fact, just the opposite happens!  (pull off vacuum line and scooter dies)

I'm going to close it up where i'm at and call it a day as it's running well and reaching proper top speed, etc.

*tps reset - with key off, open throttle all the way.  turn on the key, wait 8-10 seconds.  slowly close the throttle and turn the key off.

fin!

btw - i work on scooters regularly.  this is the first one of the models to come through my shop.

[CROSSBOLT]

It dies because the air bleed (idle adjustment) is closed. The open vacuum port is supplying the air needed for a mixture that will burn.

Karl

[Redk]

I shall look forward to an opportunity to try that TPS reset method !
Tnx !
redk