intermittent fuel flow By scoot (Read 2,661 times)

[scoot]

Hi this problem has me really stumped, the scooter will start up no problem and will run down the road for about a mile or two, than it just runs out of gas, I'll pull over and take a look at the fuel filler and it will be dry, than if I blow into the vent tube the filter will fill and it will start right up again and run for a couple miles and than do the same thing over again.at first I thought the petcock was bad so I by pasted it till I could get a new one, no luck did the same thing then I thought the carb. float was sticking so I took it apart and cleaned it and checked the float and needle all was fine than I though maybe the valves had loosened up as I had just adjusted them a couple days ago they were fine also then I checked the fuel tank looked in side as well as I could with a flash light looked fine but couldn't see the vent line opening so I blow in the hose and could hear the air .than I thought maybe the vacuum hoses where wrong as I had disconnected the PAIRS system a few weeks ago .I have one hose from the intake manifold going to a T at the T one hose goes to the carb. and one goes to the petcock but the one to the petcock is now blocked off as I'm bypassing the petcock till I receive a new one.this has really got me stumped I think I'm pretty mechanically inclined But I need some new ideas HELP PLEASE.Thanks

[Bashan]

How can the one to the petcock be blocked off and the engine run? On another note, I know you checked the vent but just for giggles ride the bike with the cap loose and see if it still stalls because it sounds like classic venting issues.

[scoot]

scoot,Bashan sorry, I mean the vacuum hose that runs from the T to the petcock. and yes I've ran it with the gas cap not in the lock position sill no go.let me go over the vacuum hoses one hose goes from the intake manifold to the T from the T one hose goes to the carb. the other goes to the petcock the one that goes to the petcock is the one that is blocked off now.hope that helps.

[Guitarman]

Sounds like you have a 'floater' in the line somewhere.
It runs fine until the floater gets too close to where a line connects and gets stuck, blocking the line.
It could be in the tank also. Now that I think about it, they are usually in the tank.
Try taking your tank off and really cleaning it.

Put some nuts in there with pure Seafoam and shake it around for a good 10 minutes.  Empty and repeat.
See how much trash, gunk, clumps of 'what the f is that' kind of stuff comes out.
Repeat as many times as needed to really get it clean.  Use a bore scope to look inside.
The local parts place might have one you can use or rent for a small fee.

[scoot]

scoot,Bashan,Guitarman Thanks guitarman I've given up for the day but I'll try that first thing in the morning.I'm going to find this gremlin one way or another.thanks for the help.later Scoot.

[cyborg]

It does sound like a classic vent issue, and also may be a vacuum drop ,, had a very similar issue with a Vespa et4 150cc,,, under full throttle load it would starve out because the vacuum would drop and the cursed auto fuel tap would close,,,,damn I hated that thing,,,,my dr350 had a similar issue with the auto valve,,, it had a small split in the dia phragm ,,,i didn't realize it till I switched over to clear lines then I saw what was happening,,,it's all manual now on both bikes,,,,,problems solved,,,now the only problem is me,,,I forget to turn on the fuel,,,,,,I'm the dummy

[scoot]

cyborg Hey cyborg, are you taking about a manual petcock because I was thinking the same way just s%@# canning the vacuum set up but I'm not really sure that's my problem because I have eliminated the petcock and the problem is still there.and what about a non cv carb.I know you like mukuni carbs. do you know any that will work on a gy6?any help would be great.later  Scoot.

[cyborg]

I put an old style VM 24 round slide on my et4,,,,best thing that ever happened to that thing,,,,got it on eBay brand new in the box for under $40,,, and it was a real live mikuni too

[rks]

Sure sounds like a vent problem to me. Is it vented to atmosphere, or still connected to a canister somewhere?

You say you have bypassed the petcock...so right now it is gravity feed.

I would fill the tank with gas, have an empty gas can ready, pull the fuel line from carb, and see if it flows well until gas tank is empty. If you get a good solid stream until tank is empty, it would eliminate the fuel line, filter, crap in tank, and vent problem.......and mean your float or needle valve is the problem.

But I feel the gremlin is somewhere above your carb

[Alleyoop]

I'll pull over and take a look at the fuel filler and it will be dry, than if I blow into the vent tube the filter will fill and it will start right up again and run for a couple miles

It is obvious the problem is in the Tank because the fuel filter is empty which means fuel has not flowed down and into the fuel filter. He says if he BLOWS into the VENT hose it then starts to flow and the fuel filter fills up again. One of two things something like a piece of the float is blocking either the VENT and or the FUEL outlet and when he blows into the VENT hose it dislodges the piece of plastic and or stirs the gas enough to make it float from the fuel outlet inside the tank. MY THEORY and I am sticking to it BASED ON WHAT HE SAID.
Alleyoop

[scoot]

scoot,Bashan,Guitarman,cyborg,rks Hi ,yea I did the tank check, flow was good it seems to be with the carb. the fuel flow is good all the way thou the fuel filter I took the carb. off again today and adjusted the float level just a bit higher to no a vale also FYI I changed the vacuum and fuel lines when I disconnected the PARS system the old hoes were old and not in very good shape when I did this the bung on the carb. was smaller than the bung on the new fuel filter so I used a smaller in. dia. hose from the carb. to the filter and a larger in. dia. hose from the filter to the fuel tank I don't know if this would have any thing to do with the flow of fuel or not .so today I replaced the smaller hose with the same size hoes as the hose from the fuel tank to the filter.(hope it doesn't leak)I also readjusted the carb.(air/fuel)and found it way off I took it for a short ride and it seems to be better but the running out of fuel problem is so hit or miss It's hard to tale.right now I'm sick of working on this problem so I'm going to wait till tomorrow and take it for a long ride and see what happens.please wish me luck, and I'll let you know how it turns out.Later Scoot.

[tvnacman]

This sounds like a phone call I got today ,I did call back and left a message .
I suggested this and also the larger one .

John

[scoot]

Alleyoop You may be on to something here, it maybe just me but my fuel Gage doesn't seem to act the same as it has in the past .but I can put compressed air in the vent hose and hear it very well at the gas cap and I can see the outlet at the bottom of the fuel tank, no blockage I don't think it's the vent because I've ran it with the gas cap loose and it still does the same thing. today as I put the compressed air in the vent hose to check I watched for dabree in the tank but there was none.this really has me stumped.is there any thing as far as the adjustment or jetting to the carb, that would cause this problem? and just as a side note I finished my new stainless steel exhaust last week but I don't dare put it on till I fix this problem or I'll just be opening a can of worms.and not know what did what.thanks for your help.(got to find this gremlin)later Scoot.

[scoot]

scoot,Bashan,Guitarman,cyborg,rks,Alleyoop,tvnacman yea and I said even with the gas cap open it did the same thing ..so it can't be the vent.

[cyborg]

We're here to help scoot ,,,don't get wild,,, we'll find this gremlin and get it out of your life,,, if we can't get it nobody can ,,I still think it's a venting or fuel delivery problem