Why is the vacuum line on cylinder #3?

I was wondering if the vacuum line could be placed in a ny other cylinder.

My bike only runs on PRIme, so I will check the line, but if that is not the issue I would like to try the vacuum in another cylinder.

I rebuilt the petcock last year so that should'nt be the issue.

My vacuum line might be melted since it is so close to the heat!

Any problems if I run the bike on PRI and put it on ON when I park it?

Any other things to check out?

Thank you!

 

The PRI will tend to flood the carbs as fuel is constantly flowing. With motorcycles, the floats are more sensitive to road bumps and turning and if you have one carb float needle not seating quite completley, then you can actually get gas in the oil and that is a whole new set of issues. If you don't have an inline filter, the oriface is so small, it tends to clog. Compressed air will fix that. An inline filter from your local cycle shop only cost a few dollars and is priceless on the headaches it solves.

 

The line is attached to #3 because that is the dedicated carb. This means that when syncing the carbs #3 is not changed. #4 is changed to match #3.
This way the vacuum can not be adjusted out making the petcock fail. It can be attached to any other cylinder so long as the bike is tuned properly.
The lack of fuel flowing means that either no vacuum is reaching the petcock or it is clogged or the diaphraghm inside the petcock is damaged. Doesn't matter that you rebuilt it, it is not functioning. The prime setting bypasses the vacuum by pushing the plunger open and allowing fuel to flow. Since you talk about the vacuum line maybe being melted I would pull it and check for damage. Sometimes they split from age and don't provide enough vacuum to operate the petcock. IF the line did in fact melt then either it is the wrong type of line or the engine is running terribly hot. It should be a fuel grade line which can withstand the heat.

 

Replaced fuel line and vacuum line, and added an inline filter.

I also got a new battery that is charging right now, and new spark plugs. Once everything is on the bike I will try.

With the petcock on PRI only a little bit of gas goes down the line, is that enough? (Just a couple drops per crank)

 

I have an inline filter on my Seca and it never fills with fuel. Even in prime. The bike still runs great though so after an initial head scratching session I decided to leave well enough alone. I replace the fuel filter every year and it is allways the same.

 

on prime it should flow freely. I bet you your problem lies in your in tank filter. I would drain the tank, remove the petcock assembly from the tank and check the internal filter. My inline filter never fills with gas completley either and my bike runs great.

 

That's about right. Fuel will flow as it is needed. This is controlled by the float valves in the carb bowls. The highest flow will be at hwy speeds.

 

Either that ... or you're actually turning the valve too Reserve and not Prime.

I see that happen a lot!

You may have also thrown the Petcock filter screen.
If the screen popped out of the petcock from where it belongs ... remove the drain screw and blow air through the petcock from where the fuel line attached to the side outlet.

Probe the Outlet with a piece of plastic weed-whacker line.