Fuel in the airbox, and thus, on my floor

[Dan]

One thing you can do while waiting for your new petcock is to check the current one.

Get two sections of hose that will reach from the petcock to the floor. Find two glass jars (jelly jars are good), run the two hoses to the two ports on the petcock into the two glass jars. Leave it overnight, see which jar has fuel in it. If the fuel port has dripped, you have a leaky o-ring in the petcock or a weak spring. If the vacuum port has leaked, you have a bad diaphragm.

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Thanks Steve - I had already done this to test the petcock, sorta. I had the tank off the bike with fuel in it, on blocks over paper towels. I did not have hoses on the petcock, but it was set on ON, where it has been for 3 days now with no leaks.

[Gorminrider]

With a full tank? Knockoff petcocks can have weak springs holding the diaphragm plug in and gravity fuel pressure can push them out..OR the petcock can be intended for a bike with some kind of pump-regulator up the line....even so, your float needles should be holding the fuel back....

[Dan]

With a full tank? Knockoff petcocks can have weak springs holding the diaphragm plug in and gravity fuel pressure can push them out..OR the petcock can be intended for a bike with some kind of pump-regulator up the line....even so, your float needles should be holding the fuel back....

Actually - I had filled the tank recently. First I've heard of this line of thought. But the tank is still nearly full, has been on my bench for 3 days, petcock in, in the ON position, with no leaks. But I'm still hoping it's the petcock. Will swap out with the OEM petcock when it comes in. Thanks

[Gorminrider]

hmm.new petcock might help , if the one you have is sticking open when the bike is running but I'd still include the float needles and seats inspected, especially if it can't hold fuel back on prime the bike will run rich in normal operation if the float needles aren't working.
There's an O ring sealing seats so cross your fingers and hope this is it but otherwise if cleaning or a desperate attempt to burnish a scratch on the seat doesn't fix(fine valve grind compound), you need the whole kit.Previous owners (curse them!) have been known to scrape away with screw drivers in there attempting to...what-get the seat out?

[Dan]

hmm.new petcock might help , if the one you have is sticking open when the bike is running but I'd still include the float needles and seats inspected, especially if it can't hold fuel back on prime the bike will run rich in normal operation if the float needles aren't working.
There's an O ring sealing seats so cross your fingers and hope this is it but otherwise if cleaning or a desperate attempt to burnish a scratch on the seat doesn't fix(fine valve grind compound), you need the whole kit.Previous owners (curse them!) have been known to scrape away with screw drivers in there attempting to...what-get the seat out?

Thanks - hoping the new OEM petcock will help. The bike seems to be running great otherwise other than an occasional downhill backfire. Will post results.

[salty_monk]

You can probably blame that backfire on the same thing.... even if it was the petcock (which I doubt) you still need new float valves and seats.

as someone said above, they should be able to hold back the full tank by themselves in theory...

[Dan]

You can probably blame that backfire on the same thing.... even if it was the petcock (which I doubt) you still need new float valves and seats.

as someone said above, they should be able to hold back the full tank by themselves in theory...

Thanks, and I suspect you're right. I pulled the carbs today and did a visual inspection of the floats and needles. There was some rust stain in the bowls, which isn't great but I assume came from the tank, but the needles and floats seemed to be clean and moving free. I didn't note anything stuck. I did not look at the seats, but the carbs were recently rebuilt so I'm hoping that's not the case. Changed the gassy oil and I'll install the new OEM petcock tomorrow and we'll see.

[Dan]

Just following up in case someone finds this later. New OEM petock installed today. And I removed the carbs and checked that no floats or needle valves were stuck. (Incidentally, removing and reinstalling the carbs was not nearly the pain in the rear it was during the rebuild. The new rubber boots have reshaped themselves around the carbs a bit, and maybe I knew what to expect a bit more.) I pulled the needles out and inspected the chambers but didn't remove the chambers or get into the seats. I didn't see any obstructions and everything seemed to move freely. I may have dislodged something small I suppose. But there is no mistake, the bike definitely runs better now. No more backfiring or sputtering, idle is smoother, acceleration is smoother. Starting is instantaneous. I didn't think it was bad before, but it's better now. I can't say for sure if it was the petcock or the floats / needles, but so far at least, no more leaks. The real test will be over the next couple of days after sitting on the kickstand.

Thanks for all the help.

[Gorminrider]

good news! It's not unusual to go through stuff twice to catch a gremlin. They are tiny critters and can hide in small corners.