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Post by GrumpyUnk on Aug 7, 2023 11:26:10 GMT -5
I do not remember what I said. If you have not checked for full diameter fuel line flow from the tank to a container, do so. Experience with small engines leads me to believe that 'stuff' can fall into the tank, slosh around, and migrate to the fuel outlet and clog up the flow from the tank into the petcock. Most petcocks have a plastic tube that looks partially made up of tiny screen material. I think it is molded that way. If grass clippings, or other, floats around or sloshes, it can move. You may be able to see into the tank if you get the right angle and observe if the outlet is gathering stuff. If so, remove the petcock and flush as needed. have fun today. tom
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timwhite74
Scoot Junior
Posts: 16
Location: Las Vegas, NV
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Post by timwhite74 on Aug 20, 2023 21:35:17 GMT -5
UPDATE: Sorry classacted and GrumpyUnk for not posting, I was out of town for 2 weeks. I did 2 things: #1. I sucked on the vacuum line that's connected to the intake elbow. I had to suck hard like getting a thick milkshake through a straw kinda suction. The fuel flowed out of the line thru the petcock and filter the full width of the line. No bubbles, or trickling... solid fuel flow. I drained the tank using that method then looked in the tank and it's clean, with nothing blocking the outlet. no crud. #2. I bent the tab on the carb bowl floater so that it's putting MORE pressure on the float needle, which does have a rubber tip (I thought it was a metal tip). RESULTS: The scooter runs consistently and is strong and fast UNTIL it runs out of gas at about a 1/4 mile (the tank is 3/4 full BTW). I'm speeding down the road at full throttle and it starts to die and no amount of throttle has an effect on RPMS or speed. I roll to a stop, hop off to look at the fuel filter, and it's empty. I start it up and have to give it a little throttle to start. I take off again, it's running great for about 1/4 mile and it dies again...empty fuel filter. If I cruise at a neighborhood speed after going fast it sputters constantly, like it's not getting enough fuel. My guess is that the carb bowl is getting full at the start then emptying and not getting filled up fast enough to keep up with fuel demand. Is this possible??? Thanks again guys.
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Post by GrumpyUnk on Aug 21, 2023 7:25:16 GMT -5
yes.
why not? if the vacuum in the intake falls, and it will due to WOT, then the diaphragm in the petcock may just comply with spring pressure and cut of the fuel flow. Change my mind.
tom
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timwhite74
Scoot Junior
Posts: 16
Location: Las Vegas, NV
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Post by timwhite74 on Aug 22, 2023 13:12:55 GMT -5
I’m not trying to change your mind, I believe you. 😁 I didn’t realize vacuum dropped at WOT. So, it seems that my initial problem is solved then? I hope. Another question, what are your thoughts on not using a petcock and just letting fuel flow by gravity from the tank? Thanks again.
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Post by classacted on Aug 22, 2023 13:29:36 GMT -5
in my opinion, the bad outweighs the good with that petcock. mine failed when I first started riding and I got rid of it. I also recommend you add in a quality shutoff valve where ever you think is best. you're lucky to have a scoot that is capable of being fuel gravity feed.
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Post by GrumpyUnk on Aug 24, 2023 7:41:21 GMT -5
Given the high qaulity of China float valves, I would want a fuel shutoff of some sort. A manually operated one would be fine. If getting something to fit into the fuel tank seems difficult, one can defeat the vacuum operated petcocks so they will flow fuel with or without vacuum. Just make the valve leak. Then install an in-line fuel cutoff accessible from one side or the other, and use it. I have had float valves fail once, on a mower. Luckily the fuel level was low, so not a lot of fuel was dripped onto the garage floor. Given that's the storage location and it is attached to the house, I am a religious user of fuel cutoff valves. So the scooter sitting over there has a cutoff, vacuum at the time, but susceptible to change if desired. I do not trust the carbs, and obviously the MANUFACTURER does not trust them either, as vacuum petcocks are standard equipment.
As far as vacuum at WOT, I think it would be close to zero. If you put a gauge on any car/truck intake, and bip the throttle, the gauge heads towards no vacuum, i.e., zero, or ambient barometric. That should allow a vacuum petcock to close. If that is true, I do not understand how these things work when driving WOT for any length of time. I got no clue. tom
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Post by classacted on Aug 24, 2023 11:35:52 GMT -5
for months I had a plastic shutoff valve on the bike. fortunately it never leaked, but this particular valve was murder to turn the on/off dial and I'm lucky it didn't break because I always had to use a tool to turn it. I do NOT recommend a plastic valve. now I use a brass valve. fantastic valve. no longer a need for a tool, but how will it fare in the long run? we'll see.
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timwhite74
Scoot Junior
Posts: 16
Location: Las Vegas, NV
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Post by timwhite74 on Aug 24, 2023 15:27:01 GMT -5
GrumpyUnk and classacted, both good points. i'll leave the carb and petcock as they are for now. I think I slayed this gremlin and see how the scooter runs for a while. With vacuum dropping at increased throttle I'm surprised the petcock system works at all. I had to suck hard on the vacuum line to get the petcock to allow flow...interesting. At least I know more now than I did a few weeks ago! thanks again for all the patience and help! Tim
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Post by GrumpyUnk on Aug 25, 2023 10:39:02 GMT -5
It may be that there are pulses as the intake gets the mix pulled into the cylinder or the crankcase(2T). That may be enough to operate or keep the diaphragm pulled down for the petcock to work. I have a Kym super 9 that I cannot get to run for more than a few minutes. Vacuum petcock. When running, I can see the flow(bubbles) of the fuel in the line, and it is MOVING when I open the throttle. If I try to ride... bzzzzzzz. dead. Seems to run out of gas. I may try bottle feeding direct from a soda bottle to see if the petcock is causing the problem. As far as I know, it could be the crankshaft seals are worn and leaking. Gotta get my smoke machine finished and find out. tom
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