fuel pick up prob

Ron j · Aug 5, 2012

my fuel hose keeps going dry. float seems to be working fine fuel tank filter and cock valve drain tank fine when carb is not hooked up. when pushing the float tickler gas will come out of air filter. but the hose will not fill when riding engine cuts out due to lack of gas. line has a rolling offset but is not pinched in any way and runs down hill the full length. is there any way to prime the line or do i have a carb or float issue???
thanks for replies
Ron j :-||

Goat Herder · Aug 5, 2012

There is many aspects to this. Does fuel flow through the fuel line when removed from the carb? Does fuel flow better when you remove the fuel cap from the tank? Might read this thread. https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNGszjRXd2kk1-8qoadc2mcc1MGaXA

Do simple things first.... See if fuel is flowing out of the fuel line from the tank. You don't need a torrential down pour out of the fuel line just a steady trickle. Enough flow for a engine that gets 100 miles to the gallon.

tooljunkie · Aug 5, 2012

if gas runs out of fuel line,its getting gas.
i pulled my in tank screen out and ran an inline filter.
i did this from new.
could be a vibration issue,or fuel cap isnt venting.l

Ron j · Aug 5, 2012

When hose is off the carb fuel runs good. When on carb and burping the float fuel will run out the air filter same when you pull out the bowl drain screw. But when running hose dries up and engine dies . Any more info to get a better petcock . I've already learned that the kit stuff is poor quality and have almost replaced all components one piece at a time.

GearNut · Aug 6, 2012

So you want a better petcock, eh?
http://www.sickbikeparts.com/catalo...ducts_id=50&osCsid=7ejmo53fjpmvtuo0460tmu1ue6

Ron j · Aug 6, 2012

Does the carb pick up fuel by just gravity or is there a vacuum siphon created by the engine pulling fuel from the carb??? Hoping that by priming the fuel line it should produce a siphon effect . Thanks for any input
Ron j

Help!!!

2door · Aug 6, 2012

It is a gravity flow system. The float/valve controls the flow. No pumps, diaphrams or suction.

It has been suggested twice that you check the fuel cap for venting. While you're riding and the fuel line goes empty, loosen the cap and see what happens. If the tank can't vent it is like holding your thumb over a straw. A non vented vessel will flow until the pressure inside is reduced to below atmospheric then you have a negative pressure effect and the fuel can't flow out.

Try riding your bike with the fuel cap loose and let us know what happens.

Tom

Ron j · Aug 7, 2012

Thanks Tom
Thought it was only gravity fed but wasn't 100% sure. I'm on my third tank first due to denting it while placing bike on a bike rack, second due to trying to rethread a badly machined stud. All three gas caps seem to vent intermittently. Also the float seems to be an issue. NT carb and the float seem to intermittently stick in the open and shut position. Took it apart today and shot it with carb cleaner but that seemed to not be the cure. Any way to insure the tank cap is venting??? And any suggestions on my float issue?? Any 411 and suggestions are welcome!!!
Thanks biker buddies.
Ron j

Road America 's Rockin Ronny

GearNut · Aug 7, 2012

An intermittently venting cap is a bizarre problem.
There are no moving parts on them. They vent through the center portion, the cup that holds the spring in place, and through a passage (sometimes many passages) created by a ribbed crimp where the pretty chrome top attaches to the underbody of the cap.
Some folks drill a teensy, tiny, itty bitty hole off center through the pretty shiny chrome top th insure that the cap will vent. This can lead to fuel weeping out of the hole as it shakes and vibrates inside the fuel tank while you are riding down the road. Just be aware of this possible side effect.

As for the float getting hung up in the open or closed position, the Brass fork that the float pushes against must be able top freely pivot on the small pin that holds it in place on the carburetor body. Check this area for anything that might cause an issue, and carefully correct it. Also the float needle, the pointy thing that the float fork operates, which is the actual fuel valve inside the carburetor, must be able to freely move inside the needle seat up inside the carburetor body.
A note for assembly: the pointy black rubber tip of the float needle goes up into the needle seat. The other metal end is what the float fork presses against.
While the following has no effect on fuel starvation it is still worthy of checking:
Check the float itself to be sure that it does not have any fuel inside of it. If it has a leak and is filling up with fuel, this will cause the float to turn into a no-float and the carburetor will flood all the time.

Ron j · Aug 8, 2012

Dear GearNut

Everything in my carb bowl seems o.k. Accidentally left the pet cock open last night and found a puddle on gas on the floor . So tank must be venting but that says the float must have stuck. The doughnut is empty and does float!! The needle valve moves easily without restriction . Should I maybe lube the jet stem and wall of the bowl??? Seems like the prob started when I cut my fuel to oil mix to 20:1. Instead of the 16:1 breaking in ratio. Not sure about it but think prob started after cutting it back! If lubing the jet stem and inside bowl sounds like an idea what should I use?? Vaseline ???
Thanks for any INPUT!!!!

Ron J
Road America's Rockin Ronny

P.S. only have about 2-300 miles on the bike.

Sent from my iPad

On Aug 6, 2012, at 23:23, "Motorized Bicycle: Engine Kit Forum" <[email protected]> wrote:

Dear Ron j,

GearNut has just replied to a thread you have subscribed to entitled - fuel pick up prob - in the Motorized Bicycle Trouble Shooting forum of Motorized Bicycle: Engine Kit Forum.

This thread is located at:
http://motorbicycling.com/showthread.php?t=41432&goto=newpost

Here is the message that has just been posted:
***************
An intermittently venting cap is a bizarre problem.
There are no moving parts on them. They vent through the center portion, the cup that holds the spring in place, and through a passage (sometimes many passages) created by a ribbed crimp where the pretty chrome top attaches to the underbody of the cap.
Some folks drill a teensy, tiny, itty bitty hole off center through the pretty shiny chrome top th insure that the cap will vent. This can lead to fuel weeping out of the hole as it shakes and vibrates inside the fuel tank while you are riding down the road. Just be aware of this possible side effect.

As for the float getting hung up in the open or closed position, the Brass fork that the float pushes against must be able top freely pivot on the small pin that holds it in place on the carburetor body. Check this area for anything that might cause an issue, and carefully correct it. Also the float needle, the pointy thing that the float fork operates, which is the actual fuel valve inside the carburetor, must be able to freely move inside the needle seat up inside the carburetor body.
A note for assembly: the pointy black rubber tip of the float needle goes up into the needle seat. The other metal end is what the float fork presses against.
While the following has no effect on fuel starvation it is still worthy of checking:
Check the float itself to be sure that it does not have any fuel inside of it. If it has a leak and is filling up with fuel, this will cause the float to turn into a no-float and the carburetor will flood all the time.
***************

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Ron j · Aug 8, 2012

Thanks for all the info! Drilled two holes right were the gas cap meets the underside with the spring cup and locks and the bike hasn't stalled yet even at 3/4 throttle for an extended time. Still think I might have a float issue but not 100% sure. Bike still likes to cycle surge and bog at WOT . Already have the carb at max lean. Haven't gone the other way on the mix yet but still think its to rich. Not quite sure how to do a spark chop or read. Pls explain proper way.

Thanks for all the info guys!!!!!!!!

MILES OF SMILES!!!!!!!!
Ron j
Road America's Rockin Ronny

2door · Aug 8, 2012

Ride at WOT, (wide open throttle) for at least a block, then shut the engine down (preferably with a kill switch) disengage the clutch and coast to a stop. Give it few minutes to cool (you don't want to remove the spark plug when the cylinder head is very hot) then remove the plug and look at the color of the center electrode and the surrounding porcelain. You're shooting for a nice chocolate brown color. Darker means you're running rich. Light tan to white and you're too lean.
Some synthetic oils will give you shades of grey as opposed to the tan/brown colors.

Tom

Ron j · Aug 9, 2012

Thanks 2door love the coup

Assume I need to pull & clean plug before the test? If its rich I have a stock nt carb have it set at max lean should look into changing the jet or go for the cns carb???
Little tiered of running for the cheap fix then having to buy the right part later . Rather fix it only once! Does it have a on carb chocke don't care for another cable on my handle bars!

Thanks
Ron j

GearNut · Aug 10, 2012

It is best to start out with a brand new spark plug, but you can do it with a used one too. A spark plug will color no matter how old it is. This is why when you do a plug chop it is important to kill the engine and pull in the clutch at the exact same time after running the engine at the RPM's in question for at least a 1/4 mile. If you let the engine idle or run at a different speed after the run and before you kill it, it will change the color print to a different color than the one you are trying to test for.

The CNS carb has a cable actuated enrichner (choke).
The CNS's can be a good carb if you like to pull your hair out and fiddle with it until the cows come home.
Folks that do all that seem really happy with it's performance when it is finally tuned up right. It is considered to be a higher performing carb than the NT by virtue of having more fuel circuits spread across a wider range of throttle positions to allow you to dial in the perfect tune for all throttle positions.

Here are a few threads concerning the CNS:
OMG I have to tune a CNS!!! Help
cns carb spacer
Inside the 2010 Grubee Skyhawk CNS Carb

george_n_texas · Aug 10, 2012

Just curious if anyone has ever tried to use an electric fuel pump? My dad told me they used to have to back up the mountain in a model T Ford because it was gravity feed. I'm sure you could run a fuel pump off a small motorcycle battery pretty easy. IDK if a 12 volt fuel pump would run off the white wire but for the little pressure you use in HT it wouldn't surprise me if it did.

GearNut · Aug 10, 2012

A vacuum operated fuel pump would be more practical. To power it all you would need is a fitting on the intake manifold, similar to one used for a boost bottle, only much, much smaller. This would provide a pulsing vacuum signal to the pump which is all they require to operate.
No battery or electrical wiring needed.
A MIG gun welding tip works very well for such a fitting.

george_n_texas · Aug 10, 2012

So ya think that sucker would work? (sorry couldn't resist LOL)
I just can't imagine how that setup would work. I may be missing something here.

Seems like to me that's pretty much what a carberater does? Sucks gas in at a pulsed rate as the engine needs it. Problem happens when the bowl gets too low and it sucks air. I guess alternatively a fellah could pressurise the fuel tank like you do a radiator when you test it.

GearNut · Aug 10, 2012

A carburetor with a float bowl does not suck fuel into the float chamber what so ever.
Here is a breif, non inclusive, simplified explanation:
It relies on a pressure system to get fuel into the float bowl. The float, working in conjunction with the float needle valve, regulates how much fuel is held inside of the float chamber.
Vehicles (or yard equipment) that have the fuel tank located above the carburetor utilize gravity to provide the pressure required to transfer the fuel.

Engines such as weed whackers, rototillers and similar, that have the fuel tank located below the carburetor utilize a fuel pump to draw up the fuel to itself then push the fuel up to or through the carburetor, even those that do not have a float chamber. Those critters are a totally different breed of carburetor, but still have a fuel chamber, it's just not float regulated which is why they have a hose to return unused fuel back to the fuel tank.
The most common fuel pump used with engines are a diaphragm style. They can be vacuum powered or mechanical powered.
As a note of reference, for many, many years automotive engines have used mechanical powered diaphragm pumps to transfer fuel from the fuel tank located under the vehicle up to the carburetor.
Fuel injected engines are an obvious exception to this design.

If you would like to learn how the fuel gets from the carburetor to inside the engine, google carburetor or more specifically Bernoulli's principal.

george_n_texas · Aug 10, 2012

Very good explanation GearNut I learned something from ya. Just curious tho do you think an electric pump would be a bad idea? I know I've swapped a mechanical fuel pump in a car for an electris was the simplest fix at the time.

GearNut · Aug 10, 2012

An electric powered fuel pump would work just as well as a vacuum powered fuel pump, only it would be more complicated and weigh alot more.
An electric powered pump requires a power source, associated wiring/ power switch, and are very large and heavy comparatively speaking.
A vacuum powered pump requires a pulsing vacuum signal as a power source ( can be sourced from the intake manifold or crankcase), can be suprisingly small, and weigh very little.
They have 3 hoses.
1. Vacuum.
2. Fuel in
3. Fuel out.
No wiring or electric motor to wear out either.
They turn on automatically when the engine is cranked over, even at hand starting speeds, and turn off automatically when the engine stops.
If the fuel tank is located below the carburetor you don't even need a fuel valve.

fuel pick up prob

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