1989 50cc wont start without help By elitecop50 (Read 733 times)

[elitecop50]

Hey all,
Newbie here. Having a small problem with my scooter starting. Here's the deal. It sat in storage for about 23 years. Got it home, flushed, cleaned, replaced spark plug, broke down carb and cleaned. replaced oil and gas and was running fine for about two weeks. Tried to start one morning with no luck. Checked fuel sending unit and is working fine. Replaced electronic choke and still nothing. The only way it will start and stay running is if I hold two fingers over the carb where the filter element attaches. it then seams to load up with gas, but stays running as I let small amounts of air pass through between my fingers. Almost as if its a vacuum leak. I cant figure this out.
Any help would be greatly appreciated.
Thanks, Mark.

[sumdawgtwigg]

I had the same exact problem with a Taotao. I cleaned the carb twice and thought it look perfect both times, and it still would do the same exact thing as you described. Finally got sick of it and bought a new carb, and it ran perfect.

[jct842]

Did you clean out the 2 jets? and the passage ways to them? You have to remove the jets to do this.

[elitecop50]

I took the carb completely apart including removing the jets and cleaned everything. Sprayed it through and made sure jets were see through. Still no luck. Made sure the float and needle seat were properly installed as well. The carbs bowl is filling with gas, so no problem there. I'm pretty skilled at rebuilding carbs and mechanically a do it all, however, I could have missed something. this thing has me stumped.

[jct842]

one of those passages is plugged. They do need an air cleaner on them to run right but if you are hand choking you have a lot more restrictions than an air cleaner.

Now that you mention it I recall just yesterday I was doing about the same thing to keep my tractor running while pulling logs, but it was intermittent and some thing is bobbing around in there. Its been that way the last 4 or 5 times I used it and I just hate to get a wrench out!

[Alleyoop]

Since you have to cut air off for it to get fuel that right there tells you, you have to much air coming in and not enough fuel. So since you cleaned the carb you may have disturbed the mixture screw settings. I do not know what type of carb you have but it needs more fuel(IF YOU DO NOT HAVE AN AIR LEAK).

If a SCREW is next to the AIR INTAKE FILTER that is a AIR RATIO MIXTURE SCREW.
TO RICHEN it up you turn it CLOCKWISE to cut some air off. ON those 1/8 turns because they are finicky to get the HIGHEST IDLE out of the setting.

If a SCREW is next to the INTAKE MANIFOLD that is a FUEL RATIO MIXTURE SCREW.
To RICHEN it up you turn it COUNTER CLOCKWISE to give it more fuel. On those turn it 1/4 turns to get the HIGHEST IDLE out of the setting.

Alleyoop

[elitecop50]

I'm all too familiar with the air/ fuel mixture. Made several adjustments with the only one on the carb, but to no avail. No vacuum leaks that I can see. The bike only has 200 miles on it. Even though it sat for 23 years, it was in a dry storage. IT was running fine up to this point.

[shop242]

Im gonna agree with alley.. Get a new carb.. or retro-fit..

[Alleyoop]

There should be TWO screws on the carb, 1 is your IDLE SPEED Screw and one the mixture. If the mixture screw does nothing then whichever carb you have AIR MIXTURE or FUEL MIXTURE the passage is clogged.
Alleyoop

[scooterbob]

Did you check the intake manifold o ring, vacuum hoses for cracking? I'm inclined to believe it's a air leak. Good luck stay with it you will solve the problem.

[elitecop50]

Alleyoop,
I completely cleaned the carb which included removing the said set screws and making sure they were not clogged. After cleaning, I blew through them with high air pressure to assure they were free of any obstructions.
Scooterbob,
I'm starting to believe it is going to be a vacuum leak somewhere. I would have this type of problem with the street race cars I built back in the day. It was usually a blown intake manifold gasket or vacuum line from the carb.
The only vacuum line I can see is the one from the gas tank valve to the intake, and that one is new. The intake gasket is hard plastic and I checked it with some dish soap and water. Guess my next step is to pony up the dough for a new carb.
Will let you guys know the outcome in a few weeks.
Thanks for all the help. it's very much appreciated.
Mark