Vacuum Petcock Question

[hkelman]

Have Wildfire 150S scooter.

I have posted twice before in an effort to diagnose my non-runnnig scooter. All suggestions have been tried including new carb, all new electrics - CDI, Volt Regulator, Coil, traced grounds and wiring. Almost ruled out electrical. At first the mechanic thought the engine was running too lean. Ruled that out with new jets & still either lean or bad spark thus the new carb and new electricals. This evening after trying all the new parts, I saw the fuel filter was totally empty. I sucked on the vac tube to the petcock as was done to prime the fuel lies when the scooter was first assembled and no fuel entered the filter. My questions are:
1: How does the petcock work? Does the vacuum suck fuel into the lines or is it gravity fed and vacuum only opens the valve?
2: Will I do any harm and will the engine run if I run a line direct from the tank to the engine to bypass and test the petcock?
2: Why is the fuel filter after the petcock and not right off the fuel tank?
3: How do I wire a small electric fuel pump and would one flood the carb?
4: Where do I obtain an electric pump that will work on these scooters.
Thank you in advance for any insight all y'all can give.

[owenbrau]

The vacuum petcock is simply a valve that opens when the engine is running, due to the slight vacuum produced by airflow through the intake manifold. If you suck gently and no fuel flows, it's bad. I'd try a better quality petcock before going to a electric pump. Running the hose without a petcock could over-fill the carb bowl, as could a pump, if the float valve doesn't seal perfectly.

[hkelman]

WOW! Quick response! Thanks. I assume from your answer that the valve opens and fuel flows by gravity rather than being forced by mechanical or vacuum means.
Where do I obtain a better quality part? Price not an issue at this time since I already have spent as much as I bought the bike for trying to fix it. I am committed now. I WILL get this thing running How do I know it is a better quality part?

[WildMan]

hkelman
I have 2 150cc scoots, I just worked through the same issues.. If your gas tank is above the carb, get rid of that vacuum petcock & run new 1/4" corded neoprene fuel line from gas tank to 1/4" in line fuel shut off valve from like Briggs & Stanton (you can get them from Napa), then 1/4" fuel line from shut off valve to a new disposable fuel filter, then run 3/16" corded neoprene fuel line from filter to carb inlet (keep 3/16" hose short, only enough to get filter 2 -3" from carb, 3/16" hose will stretch for 1/4" filter).. Keep every thing short as possible, also pay very close attention to the hose clamps you use and DO NOT OVER TIGHTEN if using worm gear type hose clamps.. If you over tighten hose clamps they will stretch the end of hoses causing hoses to suck air, air then causes VAPOR LOCK at the filter.

I replaced fuel lines 3 times before I figured out that over tightening the hose clamps was stretching the end of the hoses.. And shortening the length of fuel line to just the distance from the gas tank to the carb & no more, only then did I finally get rid of the air lock, & finally get filter to fill w/ gas..

Hope this helps..

[trigger]

WOW hkelman, I feel for ya.

Forget about the petcock for now, you have enough parts. bypass it with either another fuel filter, or a couple of hose connectors that you should be able to find at an auto parts store.

When I was tuning my 150 I ran this way for a couple of days, no problem, but you will want to go to one fuel filter when you figure it out. Now if your tank is above the carb it is gravity feed. Your carb has a float bowl cutoff that will prevent flooding during your testing, but when you are done you will need to put some type of fuel shutoff valve inline, so you are not relying entirely on the float cutoff.

I suspect a intake vacume leak. Remove it from the engine and inspect it carefully. Look for cracks or a missing O ring where it mates with the engine. There should also be a gasket or spacer between it and the engine.

Good luck, I will check back later.

[trigger]

PS. The vacume valves are fairly reliable, and easy to test, most pass a little gass (pun intended) even with the engine not running.

[njyuriy]

Hi! Here is the link to my problem,unfortunately I removed all the pix already.
Hope it helps!
scootdawg.proboards.com/index.cgi?board=talk&action=display&thread=25238

[DaveR]

hk,
Had the exact same problem on one of my scoots.. easy to test by just bypassing the petcock and make sure it runs fine.. I would only do that for testing though, then replace the vavle asap.. The manual valves others talk about are great, but if you forget to shut it off your carb could easily dump all your fuel on the ground if you get a speck of dirt in your needle and seat.. here is a link of one on Ebay.. I purchased a spare online and it works fine.. cgi.ebay.com/ebaymotors/New-Fuel-Pump-of-ATV-50cc-150cc-Moped-Scooter-Roketa_W0QQcmdZViewItemQQ_trksidZp3911Q2ec0Q2em14QQhashZitem25563422b1QQitemZ160360047281QQptZLHQ5fDefaultDomainQ5f100 ....
Good luck, Dave
PS: Just make sure when its running with the valve bypassed to check and make sure your getting vacuum to to valve from the engine.. It won't feel like much, but it doesn't need much to open..