Help: Fuel Leak

[Ron-P]

I'm new to motor-bicycling and these engines so I'm not sure if small leaks
are normal or not. I bought the bike with 36 miles on it. The owner had
a mixture of 20:1, I drained it and put in 30:1. I've notice an increase
in the leaking, but not 100% sure if it's due to the change in fuel/oil
mixture as I'm riding it much more since I've changed the fuel.

My best guess is the leak is coming from the air intake. I took off the
air filter and it had some fuel on it and a small puddle at the base
of the air filter housing. I cleaned and dried it and rode the bike for
a mile. I check and there's a small amount of fuel puddled again,
behind the air filter.

It seems to be dripping from behind the air filer, down the bikes seat
shaft and dripping on the base of the bike where the kick-stand is
mounted.

It's marked by the purple boxes in the pics below.










Also, in the top pic, to the upper left corner of the purple box there is a small
screw with a spring, can someone tell me what that does?



Happy Motoring!

[georgeknight]

Might check to see if your float is too high. I had to lower mine when I first got my bike together. The button with the spring is a primer. I never use mine my bike starts up without having to use it.
Hope this helps...........George

[Ghost0]

That is actually pretty common. It is most likely blowback from your intake. Since these engines don't have a reed valve the intake is open until the piston closes it. It will tend to blowback some of your intake charge. Once you break the engine in and running less oil it won't be as apparent. You may also be running a bit rich. After break in, get a new plug and check your mixture. You may want to go a little leaner, lower your needle by raising the e clip.

[Ron-P]

Thanks guys, but, I'm not sure what / or how to, adjust the float or lowering the needle and raising the e clip. Any chance you could point me in the direction of how to adjust these?

Is there any where I could locate an instruction manual / assembly manual for these engines that might help me get familiar with them.



Happy Motoring!

[seca40]

I"ll give it a go.

The float is inside the bowl shaped portion at the bottom of your carb. It functions the same way the float in the tank in your toilet does. It regulates how much fuel your carb has imediately available by opening and closing a tiny needle valve. When your bowl is low on fuel the float sinks. The needle drops with it and opens the inlet allowing fuel to flow in to the bowl. When this happens the float ... well, floats up and takes the needle with it eventually closing the valve. If your float is mal-adjusted it won't close that valve until after the bowl is too full causing a little fuel spill. I don't know if there is a known position that works for these carbs. If the problem is your float, you will probably have to do the ol trial and error thing. The float is on a thin metal tab. Bending the float down will lower the fuel level in the bowl. Bending it up will raise it. Make small adjustments.

Ghost o is probably right though. It may just be blowback accumulating in the air cleaner. Mine does the same thing.


The jet needle rides in the center of the carbs slide. The slide is the cyclindrical thing that goes up and down in the center (venturi) of you carb when you twist the throttle. If the air cleaner is off you can look in the hole and see it. The jet needle and needle jet work as a pair. When you twist the throttle the cable pulls the slide up taking the jet needle with it. As the tapered needle is pulled up out of the jets orifice it allows more fuel to pass into the air flowing through the venturi and past the slide. The slides movement regulates airflow. So, the position of the needle relative to the slide determines the ratio of fuel; air entering your engine. The needle is held in place by a tiny e - clip. The clip locks in to a groove in the needle. Raising the clip to a higher groove lowers the needle keeping the jet blocked a little more. This will lean your mix. More air less fuel. Lowering the clip raises the needle opening the jet more. This will richen your mix. More fuel less air. Now, how do you know what your engine wants mix wise? By reading your spark plug. If the electrode on your plug is oily, black, goopy. Your mix is too rich. Raise the clip a notch lowering the needle leaning the mix. If your electrode is very clean or white your mix is too lean. THIS WILL KILL YOUR ENGINE !!! Too much air and not enough fuel means not enough lubrication and an early death. Lower the e-clip raising the needle adding more fuel to the mix. Your plug should be the color of delicious chocolate milk.

Here's a chart

Spark Plugs

Make sure you don't have any air leaks before hassling this.

These might help too.

http://motorbicycling.com/f6/vendor-...uals-3536.html

Oh yeah. The screw with the spring on it is your idle adjustment screw. Screw it in and it raises the slide. More air/fuel. When you have the slide out, notice the 45 degree groove cut in it. That is where the screw lifts the slide.

[Ron-P]

Awesome, thanks seca40.

[Norman]

the classic posts will help it has pictures and other goodies there I know I did some of it.
Norman

[stude13]

you did a very nice job of illustrations. i noticed the cap nuts, toss those shown and the others too, replace with good nuts and lock washers and blue locktite.

[Ron-P]

I will, thanks for the tip.

[Dave31]

Running out of time here...Use these pics along with Secca post to help U out