Fuel Petcock to Engine Head Connection?

[MidnightBlue]

I bought what was supposed to be a replacement fuel petcock for my '86 500. The old petcock had a rubber hose that ran from the diaphragm of the petcock to a nipple on the cylinder head. The new petcock does not have that connection. Can this simply be capped? What is the purpose of this connection at the head?

On a sad note, I will probably sell the bike because I won't be riding it much. I'm planning to sell a bunch of things in order to simplify my life and hit the road as a musician. I just don't want to sell this bike with a problem.

[MidnightBlue]

Here is a picture of the old petcock next to the connection I am talking about and and new petcock without the connection.

[gat803]

Your original petcock was, to a degree, vacuum operated. It was a safety feature that allowed gas to flow only when the engine was spinning....the engine vacuum pulled open the valve.

Since the new petcock doesn't have this feature, cap the vacuum port on the head and go on your merry way.

[gat803]

I should probably elaborate.

The ability to shut off the flow of fuel at the tank is important for more than the obvious reason. That reason being removal of the tank without draining.

Inside the carburetor is a small valve known as an inlet needle. This, in concert with the float, is what lets gasoline into the carb bowl and hence, into the engine to be burned. If this valve is working properly, when the engine is shut down or it has enough fuel for the current load demand, the inlet valve closes.

The problem is that if this valve becomes dirty or defective it can continue to pass fuel when it isn't supposed to. This can lead to potentially huge problems if the engine fills with gas.

The petcock, if closed when the engine isn't running, makes filling the engine with gasoline impossible. Now, this condition does isn't overly common, but it does happen. There are those riders that turn the petcock to off every time they shut off the motor. There are also those that never turn off the petcock....

It's up to you.

[MidnightBlue]

Thanks so much for the response.

[MidnightBlue]

I installed a new fuel line and I capped the vacuum port. After a test ride, everything seems to be fine except the damn rubber cap is orange so I will have to paint it. There's always something to paint...

I will also have to file down the handle on the petcock in order to clear the bottom lip of the tank, otherwise it will not full switch to RESERVE.

It is quite a nice day for a ride! Thanks!