Topic: Carburator overflow issues

[eigenvector]

I ask this here because I find that of all the forums on motorcycles - this is the only one that people consistently offer opinions on.

On my Sabre I discovered that the petcock was leaking, I "fixed" it by creating a new gasket for the petcock - that fix apparently didn't work.

Go to start it and it refuses to budge.  On a lark I pulled the front right spark plug and cranked it again.  Gas goes spewing out of the hole.  Yup - gas filled the cylinders on the front 2 cylinders.  Guess I have some work ahead of me.

So here's my real question - wasn't the carb bowl overflow tube supposed to catch that?  I know those overflow tubes are clear - so how was gas able to drain into the cylinders and bypass the overflow?

Just for reference - on the Sabre the front two cylinders are positioned under the carburetors.
http://thumbs3.ebaystatic.com/d/l225/m/mkmhRm2shHBI4VoECYhEc_Q.jpg

You can see the cylinders on the lower left of the image.

[dragracer]

Curious, is this a vacuum activated petcock? If so, was the diaphragm torn or removed? Should either be the case, fuel is constantly running out of the tank, into the carb and then likely overflowing into the cylinders- not good. Get a good petcock if this one isn't properly working. Verify that the float isn't sticking in the carb(s) allowing fuel to overflow into the engine. Also, does the petcock  have a "prime" position? This typically allows fuel to bypass the hole normally open through the diaphragm activation.


Mind you, I'm not familiar with the Honda petcock but my KZ 1000 petcock of the same era was set up in this manner. Regardless, no matter what you do, don't try to crank the engine again until you remedy this problem. Hydraulic lock from that fuel in the engine can cause bad things to happen.

Just my 2 cents.