Won't stay on! By purplebeanie77 (Read 1,233 times)

[purplebeanie77]

So my 139qmb scooter 80cc bore kit, new racing cdi, new racing intuition coil starts but it won't stay on until I hold the gas at one exact point. I also have to play with the throttle to get it to start. My timing is good, I cleaned the carb 2 weeks ago and when it's on the back tire doesn't move. I'm not sure what to do as a next step. It's been sitting for two weeks.

[Alleyoop]

Its a Fuel Ratio Mixture problem is all. Cannot see cause the video is to dark but what type of Air Filter do you have attached? The other thing you can do is Turn the FUEL RATIO MIXTURE screw clockwise until it stops and then Turn it Counter Clockwise 2 1/2 turns and see if it wants to start better and stay running.

Once you get it to stay running just let it idle and warm up about 5 minutes then adjust the carb.
Alleyoop

Here is the procedure to follow it is a step by step and how to.
scooterdoc.proboards.com/thread/1499/4ts-carb-tuning

[purplebeanie77]

There is no fuel ratio mixture screw

[jerryscript]

The air/fuel mix screw is probably capped with a brass plug. It is located on the top right of the picture, so when standing on the left side it is on the lower side near the front. You can drill a small hole in it, then use a screw to remove it.

[Alleyoop]

Well you have TWO choices buy a aftermarket carb for around 25 bucks. They do not have the Fuel Ratio plugged drill out eh plug to get at the screw.
Here is how to take the Fuel Ratio Mixture plug out.
Alleyoop

[purplebeanie77]

So after you do that there is a screw under there? I might just go buy a80cc carb I have the upgraded jet in this one!

[Alleyoop]

Yep, they plug up the screw so customers cannot change the LEAN setting to pass emissions for the EPA.
There is no 80cc carbs for the 50cc motors. The 50cc scoots come with a 18mm carb which is what is on yours and you can buy 19mm and 20mm. But your problem is not the MAIN JET its the PILOT JET and the ability to adjust the fuel mixture to match the amount of air coming in.
Alleyoop

[purplebeanie77]

Oh well I'll try getting into that cap but I have no drill

[Alleyoop]

You see in the VIDEO he drilled it a little then used a Pointed Screw to screw into the drilled hole. Well you can Get a small pointed screw and maybe tap it it into the center of the plug IT IS BRASS and it is soft and see if you can use a screw driver to see if it will grab and the plug will turn then maybe you can work the plug out.

Or you can get a cheap drill and a small bit set for about the same as an aftermarket carb will cost you.
Alleyoop

[jerryscript]

The last one I pulled out, I took one of the body panel screws, tapped it gently with a hammer till it just punctured the brass, then turned the screw with a screw driver and it popped right out, 10 seconds and done!

Alleyoop, I think you left the s in https when you posted that video, which prevents it from playing while embedded.

[purplebeanie77]

I'm using the phone app to post the video! I'll add it in next time tho! I'm about to try to get that cap off now

[purplebeanie77]

Jan 8, 2016 19:02:50 GMT -6 Alleyoop said:

Its a Fuel Ratio Mixture problem is all. Cannot see cause the video is to dark but what type of Air Filter do you have attached? The other thing you can do is Turn the FUEL RATIO MIXTURE screw clockwise until it stops and then Turn it Counter Clockwise 2 1/2 turns and see if it wants to start better and stay running.

Once you get it to stay running just let it idle and warm up about 5 minutes then adjust the carb.
Alleyoop

Here is the procedure to follow it is a step by step and how to.
scooterdoc.proboards.com/thread/1499/4ts-carb-tuning

Now I have removed that brass cap what way do I turn it

[Alleyoop]

To try to get it to stay running so that you can fine tune it DO THIS:
A. Turn it clockwise until it stops AND COUNT THE NUMBER OF TURNS IT TOOK TO STOP.

1. If it took 2 TURNS OR LESS to stop THEN TURN IT COUNTER CLOCKWISE 3 turns.
2. If it took 3 TURNS OR MORE to stop THEN TURN IT COUNTER CLOCKWISE 2 turns.

You need to at least set it so that it stays running so you can fine tune it after it warms up.

[purplebeanie77]

It turned about 3 times and I turned it back 2 1/2 so when I get home I'll try turning it till I can get it to stay on

[Alleyoop]

Great, that is what I thought it needed !! Since you had to open the throttle at a certain position it needed more air IT is getting to MUCH FUEL. So turning it CLOCKWISE to LEAN it out a little will help.
Alleyoop