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Post by bigmac on Jul 17, 2015 12:47:20 GMT -5
About two years ago, I bought a new vacuum operated fuel shutoff valve because my old one appeared to have some gas leaking into its vacuum line. My fuel filter has clear, see through plastic and is between the shutoff valve and carburetor. Before getting this new shutoff valve, I would see that the fuel filter was always full of gas after every ride. However, with this new one, the filter is always around half full after every ride.
When I turn the engine over by hand with the kick start lever, I do see drops of gas fall into the filter. I even turned it over until the filter was completely full without an air pocket inside, but it went back to being partially full after the engine started.
Is this normal for these vacuum operated fuel shutoff valves?
I think this shutoff valve is being too restrictive and not allowing gas to flow freely enough. Also, I noticed if the engine speed is high for about a minute or more, it starts to act like it's running out of gas.
These shutoff valves are cheap, so I could easily get another one. I just want to find out if this one is indeed not working normally before getting another one.
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Post by nimajneb on Jul 17, 2015 12:58:14 GMT -5
The filter should be before the vacuum shut off... that way nothing can get into it and clog up the valve. if your worried about it buy a manual shut off valve. Thats what im doing so i dont have to replace it so often.
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Post by bigmac on Jul 17, 2015 14:02:48 GMT -5
I always assumed it would be better to have the fuel filter before the shutoff valve to prevent a clog. My scooter came with the filter after the shut off valve and I never changed it. Perhaps I will get some fuel line and change that setup in the near future.
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Post by nimajneb on Jul 17, 2015 15:16:27 GMT -5
Thats weird mine came before the valve. I know that some people put one after and one before. But i figured that would slow down the flow. maybe some more people will chime in and we will find out...
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Post by keikara on Jul 17, 2015 15:25:41 GMT -5
When my scoot was new it only had the filter before the vacuum operated pump, after about 300 miles my carb's float stuck open, when the dealer fixed it he put another one after the pump. I also noticed the filter after the pump never filled completely, and eventually I had issues where the scooter was running out of gas to the carb, removed the filter after the pump, and have no more issues since.
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Post by geh3333 on Jul 17, 2015 17:58:19 GMT -5
I always assumed it would be better to have the fuel filter before the shutoff valve to prevent a clog. My scooter came with the filter after the shut off valve and I never changed it. Perhaps I will get some fuel line and change that setup in the near future. What up bigmac !! , just buy a manual shutoff valve . they are much more reliable. |
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Post by cyborg on Jul 17, 2015 19:35:31 GMT -5
I'm all manual on all my machines now,,,sick of the vac valves leaking not working whatever the story is today
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Post by geh3333 on Jul 17, 2015 20:05:19 GMT -5
I'm all manual on all my machines now,,,sick of the vac valves leaking not working whatever the story is today Its nice having all vacuum lines sealed off. One less thing to worry about. |
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Post by bigmac on Jul 18, 2015 13:18:05 GMT -5
Alright. I'll look at some of the manual shutoff valves then.
I just did an oil change and air filter cleaning because I'm pushing 4,000 miles now. I really don't want to do work of any kind to it until the 5,000 mark, especially since my whole headlight fiasco. I've had this vacuum operated valve for about two years now, so I can live with it until then.
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Post by geh3333 on Jul 19, 2015 23:20:48 GMT -5
Alright. I'll look at some of the manual shutoff valves then. I just did an oil change and air filter cleaning because I'm pushing 4,000 miles now. I really don't want to do work of any kind to it until the 5,000 mark, especially since my whole headlight fiasco. I've had this vacuum operated valve for about two years now, so I can live with it until then. You say " an air filter cleaning " . what type of air filter and how did you clean it ? If it is a regular stock type air filter , then there is no cleaning , only buying a new one . those things lock in dirt and dust and if you used water to clean it then its probably toast. |
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Post by bigmac on Jul 21, 2015 13:26:05 GMT -5
You're suppose to buy a new one each time? I have the stock filter. It's a foam type of filter. The owner's manual says to wash it by hand with soap and water every 1,000 miles and oil it with motor oil afterwards, then replace it every 5,000 miles.
I haven't noticed any issues with cleaning foam filters instead of replacing them.
My Briggs & Stratton lawnmower has a similar type of foam air filter. That filter sometimes gets dirty to the point at which the mower begins to run rich, but it goes back to running properly after cleaning the filter with soap and water.
My Yamaha Zuma also has a foam filter for its CVT. Owner's manual says to clean it with a solvent every 2,000 miles.
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Post by geh3333 on Jul 24, 2015 2:27:31 GMT -5
You're suppose to buy a new one each time? I have the stock filter. It's a foam type of filter. The owner's manual says to wash it by hand with soap and water every 1,000 miles and oil it with motor oil afterwards, then replace it every 5,000 miles. I haven't noticed any issues with cleaning foam filters instead of replacing them. My Briggs & Stratton lawnmower has a similar type of foam air filter. That filter sometimes gets dirty to the point at which the mower begins to run rich, but it goes back to running properly after cleaning the filter with soap and water. My Yamaha Zuma also has a foam filter for its CVT. Owner's manual says to clean it with a solvent every 2,000 miles. OK , if its a foam filter then its ok to clean . most stock filters are the paper type, but since yours is foam , your in good shape. |
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Post by bigmac on Jul 29, 2015 20:16:35 GMT -5
I was wondering, does anyone know how narrow of an opening a vacuum operated fuel shutoff valve has when suction is applied? I'm sure it varies between each shutoff valve, but do you think it's extremely small?
I'm curious about the odds of a clog occurring in one of them since debris I've seen in gas cans and gas tanks don't look much larger than grains of sand.
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Post by bigmac on Dec 20, 2015 14:44:16 GMT -5
Turns out the vacuum operated fuel shutoff valve was the problem.
The shutoff valve's diaphragm broke, causing gas to get sucked down its vacuum line. I know it's bad, but I put on yet another vacuum operated fuel shutoff valve. I was able to get one for free from someone I know, so I took it. Now the engine can run at high speeds without beginning to act like it's running out of gas, so the previous shutoff valve must have been too restrictive.
The diaphragm broke at a friend's house, 17 miles away. It seemed normal when I arrived, but when I started the engine upon leaving, the engine surged way up, then stalled right afterwards. The scooter was able to crawl back home though.
The next day, I hooked a clear vacuum line to the shutoff valve and turned the engine over with the kick start lever. I watched as a lot of gas flowed into the vacuum line. Gas was even dripping off the bottom of the shutoff valve. I'm surprised it was able to run at all with that much gas being dumped into the engine.
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Post by dollartwentyfive on Dec 20, 2015 16:22:12 GMT -5
vacuum shutoff valves for 50cc engines shouldn't pose much of a problem.
mine never gave any problems.
the issue arises with 250cc engines, and probably 150cc too.
i simply had enough of the constant WOT then release.
twist fully open, then having to close the throttle.
finally tossed the vacuum valve and at first got an electrically operated pump.
i do not recommend a electrically operated pump.
i went to NAPA and got a manual valve for a briggs and stratton engine.
you need to be aware of shutting off the fuel EVERY TIME you get off your ride.
carb floats usually work pretty good at shutting off fuel flow, but sometimes they stick open.
combine that with a particular position of the combustion cycle and you can wind up with an engine full of gas.
i finally eliminated all of my vacuum lines except for the air cutoff valve.
i would have eliminated that one too but i didn't like my scoot back firing on closed throttle.
6 inches from fuel tank outlet to carb inlet is sufficient for constant fuel flow for a 250, even at WOT.
the reason i don't recommend an electrical pump is because of the pressure of the fuel.
i found this out the hard way.
i didn't get one of my band clamps tight enough and the fuel line to the carb blew off at speed.
my chines scoot just up and died, and there i am thinking "what now?"
so i park the ride, raised the seat, and started looking around, then finally noticed the stream of gas shooting out of the fuel line.
that could have been a very bad situation.
OTOH, some type of pump will be required for a tank below the carb inlet.
just be careful with an electric pump.
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