Big Chief scooter starts and dies? I need help!

[sonarbiscuit]

Hello everyone,

first of all these forums have been very helpful in troubleshooting my scooter however it's not enough. I hope that you all can help me solve my scooter woes with this post!

I purchased a used Big Chief 50cc four stroke scooter (for $180 I couldn't resist!). I was told that it needed some carburetor cleaning so I went ahead and did so.

Before and after cleaning the carb, the scooter would start up, idle for around 30 seconds and slowly die. I would give it gas and it would slowly die too.

The electric choke was not working so I purchased a whole new carb which came with the electric choke for a reasonable price. I put it in and the scooter started right up. Again, 30 seconds later the scooter would slowly die! I've adjusted the idle speed and the fuel mixture screw which may have helped a bit but the scooter still dies. Here is what I've done so far:

Spark plug is in working order
New fuel line and fuel filter to the carb
Replaced the old carb with a brand new carburetor
Seafoam carb cleaner added to new gas
Gas is getting to the carb properly
Added new oil


Here are some things that I haven't investigated:

The automatic choke has two wires: green and yellow and plugs into the scooter one way using a plastic connector. When plugging the automatic choke into the scooter plug (only one way to plug it in), the yellow connects to green, rather than green plugging into green. I removed the plastic connector and connected the green to green and yellow to yellow. This didn't seem to make any difference. Polarity problem? I tested the voltage and the scooter is supplying power to the choke.

The air filter box has a tube 1.5-2 inches in diameter coming off of it which extends towards the front of the scooter about six inches. It came like this and maybe it is supposed to connect to something?

There is also a tube extending from the metal plate cover of the kickstart (magnito?) which also isn't connected to anything.


Sometimes the scooter idles at a rather high speed and sometimes is starts up idling low.

Anyway, thanks for reading and any advice is much appreciated. I've pretty much given up but maybe there's hope!

[jimh]

How many miles are on this scooter may determine whether it's ready for a valve adjustment...

[sonarbiscuit]

My apologies, forgot to mention that. The scooter has about 1300 miles on it. I'm assuming that this isn't a lot of miles but then again it's my first scooter so I don't know!

[D-cat]

There are various possibilities. The autochoke is AC so wire polarity isn't one of them.

Possibility 1: Tight Valve(s) - take the valve cover off and adjust the valve gaps appropriately. .004" each (double manual spec) is what I like. Many tout the benefit of .005" exhaust.

Possibility 2: Fuel Delivery - petcocks and fuel filters crap up just as easily as carbs, so replace the filter and test the petcock, replace if it fails. Also double check that your carb's float needle is sliding freely and that the float isn't set too low. You may need to do a more thorough carb cleaning (Carb Cleaning 101).

Possibility 3: Ignition component failure - I doubt it with a 30 second predictability and a slow down before quit, but can't ignore it just because I don't like it. If you have a multi-meter you can monitor for a spark pulse out of the CDI, see if the signal gets weak or dies as the scooter is dying out (this will not catch a spark plug or ignition coil failure, but will verify at least that the CDI and other associated coils are working).

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Pin 2 (typically Green/Yellow or Black/Yellow) is the output to the ignition coil. It delivers pulses in excess of 120V to the ignition coil.

[D-cat]

BTW forgot to mention: don't worry about those intake hoses that don't go anywhere. Their job is to draw air from a location that isn't going to suck in a ton of water, mud, bugs, etc... just somewhere between the floor panels is generally fine.