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What are the reasons for having to rebuild a fuel petcock? Does it become plugged over time in the same way that carb jets do?

The reason I'm asking is that my bike will run dry (of fuel) if the petcock is left in the ON or RES position (obviously stalling when the bowls eventually empty), but it WILL function in the PRI position.

Unfortunately, it slowly starts to flood the carbs if left in PRI when riding. And also eventually stalls (epecially if the throttle isn't wide open).



Any input?
Thanks in advance.

maximnewb wrote:What are the reasons for having to rebuild a fuel petcock? Does it become plugged over time in the same way that carb jets do?

The reason I'm asking is that my bike will run dry (of fuel) if the petcock is left in the ON or RES position (obviously stalling when the bowls eventually empty), but it WILL function in the PRI position.

Unfortunately, it slowly starts to flood the carbs if left in PRI when riding. And also eventually stalls (epecially if the throttle isn't wide open).



Any input?
Thanks in advance.

It sounds like you have more than just one problem. Let's start with the carbs running dry of fuel when riding in the ON or RES position.

ON and RES function when there is engine vacuum applied to the petcock. If there is no vacuum to pull open a diaphragm in the petcock, no fuel flows. This could be solved by either a good cleaning or a petcock rebuild. I'd say rebuild it, parts are usually inexpensive.

The next problem is when the carbs overflow. They will only do this if they cannot stop the fuel from filling them, which is controlled by the float needles and seats. The needles like to wear out on those and they are pretty pricey to replace, but I'd put money on that being the overflow problem.

I would also venture the stalling problem is related to the needles and seats. I recommend giving this page[/url and [url=http://www.dansmc.com/carbs2.htm]this page a read.

Good luck, keep us posted.

could it be that there is no vacumm?

and that the petcock is fine?

maybe u shud check the vacum in the carbs no?

im really new to vaccum fed carbs so correct me if im wrong

sidecarguy wrote:could it be that there is no vacumm?

That's what I think too. Make sure your vacuum line is connected from one of the ports on the carbs (usually the 3rd one on a maxim) to the small port on the petcock. Additionally, make sure the line has no cracks or cuts and it is not pinched anywhere.

Skier wrote: The next problem is when the carbs overflow. They will only do this if they cannot stop the fuel from filling them, which is controlled by the float needles and seats. The needles like to wear out on those and they are pretty pricey to replace, but I'd put money on that being the overflow problem.

Sometimes an accumulation of crud can form in between the needle and the seat. This will cause symptoms that you are describing and only requires a thorough cleaning to fix.

You can tell if your needles are worn by looking at the rubber tips. If they are notched or cut or something, or the spring is worn out inside the needle, then they are bad.