Not a gs500 question, but you guys seem to know a lot more than me....
I have a 250cc (cf moto v3) that isn't getting gas.  I rebuilt the carb, and replaced some the gas lines. Problem is that the gas line coming out of the vacuum regulator/diaphragm is dry. It's gravity fed, the vacuum controlled diaphragm inline between tank and carb. (I'm assuming it's to prevent the carb from overflowing when the machine is off.) The outlet side to the carb of this device is bone dry. Tank is full, line out is full.

Thoughts on how to get the gas flowing?

Remove the device and run a straight line to the carb? Use a hand-held vac pump to simulate vac? Something obvious I'm missing?

Most vacuum activated petcocks have a prime setting which should allow fuel to flow through without vacuum.

The vacuum setups are a cool idea as you don't have to set the fuel to "off" when you park the bike, but they totally suck once they stop working which they all seem to do.  I'd just bypass it.

Don't just remove the valve and run the line straight into the carbs, I'd replace the vacuum valve with an on/off ball valve.  If you can't find one locally they are found online easily enough.

You also have to plug the vacuum line out of the carbs.  Just cut the hose shorter, kink it, and tie it off, or get a little rubber plug for it.  They are cheap and can be found at any auto parts store.


Does your bike have a reserve line?  If so I'd suggest running 2 on/off valves and a T-fitting so you don't lose reserve function.  You can see pics of how I set up my GS500 in this thread: http://gstwins.com/gsboard/index.php?topic=68991.msg830278#msg830278

Works much better than stock, and is a lot easier to work with.

There's no reserve line, or petcock/shut off switch. Single line w/vacuum device only. Been thinking about installing a shut off switch mainly for maintenance ease.
I'll try bypassing and gittin' this thing running already!

cheers!

Just don't go straight to the carb without some sort of shut-off

why not straight to the carb? safety reasons?

For safety in case a leak starts and because it just takes a micron of dirt to old open your float needle. If you have your fuel turned off when that happens your bike may spill a little gas. If you run the line straight to the carb when that happens it will empty your gas tank completely. Or when you park on a steep hill, etc.

So I ran a direct line from the tank to the carb. Still no gas inside the carb. I checked the rubber plunger w/the pin at the end, moves freely. Checked for adjustment on the floats, (no adjustment needed) and made sure the mixture screw was out a couple turns. The carb is completely bone dry, not even the smell of gas. The rebuild kit was spec'd for this bike, and everything fit perfectly, but if there was a problem the carb would at least have gas in it.
When I took the carb apart the only problem I saw was crystallization in the float bowl. Otherwise it looked very clean.

I'm going to try and blast some carb cleaner into the main fuel port, in case of blockage.

Any other ideas?

Rebuilt the carb for a 4th time!  like being in the military where you have to take apart and rebuild your gun over and over.... i think this time it worked. the needle (?) under the floats was either stuck or a blockage right near it. blowing it out w/compressed air helped.
when i hooked up the gas line i could hear the carb filling. glug, glug, glug....i thought it was running out onto the garage floor! couldn't start it though, too loud and too late (neighbors.)  still a win!

maybe now i can start the tuning process.

[attachment deleted by admin]