GY6 stalls immediately after starting

[eriswerks]

Hello all... I purchased a 150cc GY6 scooter about a month ago, and have been doing battle with the thing ever since. This board has a lot of good information, and I've tried a few things I have seen here to fix my problem, but I figured it's time to ask the experts.

Just like the subject says, the scooter consistently stalls out within a few seconds of starting. If I touch the throttle during those few seconds it is running, it will stall instantly. It began doing this about a week after I got it - prior to that it was fine.

Here's what I have tried so far: checked and re-checked every hose, checked the gas, changed the fuel filter, adjusted the idle screw, adjusted the mixture screw, changed the petcock valve, disassembled and thoroughly cleaned the carb, and replaced the spark plug just for fun. I live in Florida, by the way, so cold weather is a non-issue.

Cleaning the carb had no immediate effect, but the day after that it started working fine again for no apparent reason, for about two days. Then it went back to its usual stalling behavior.

I knew zero about engines when I got this thing, but it seems like I'm destined to learn whether I like it or not. Does anyone have any ideas on what I might try next?

Here's the specific scooter I own, if you'd like to see:
www.scooterdepot.us/Moped-150cc-Gas-Scooter-New-Design-p-430.html

[harrywr2]

1) Check for a cracked or loose intake manifold. Spray some starting fluid at your intake manifold while idling...it should not make a difference. The changed to carb didn't make a difference until a the day after leads me to think maybe a loose airbox or manifold As you would have to reseat both if you took the carb out.

2) Valves have been known to ship from the factory maladjusted.

Valve adjustment thread here...
scootdawg.proboards59.com/index.cgi?board=talk&action=display&thread=4344

[timmyjane]

try the ignition coil. sounds crazy but i had one not long ago that was doing the same thing. i changed the carb 2xs, new plug, cleaned fuel tank, replaced petcock, did a valve adjustment, new cdi and a new intake. turns out it was the ignition coil.

[eriswerks]

Thanks to both of you for the suggestions. Yesterday I tried spraying some carb cleaner on the air intake, and where the manifold meets the carburetor, to see if anything is cracked or loose. That didn't give any result, so today I think I'll try the valve adjustment.

If that doesn't do anything, I'll look at the ignition coil next. Did your problem come and go too, timmyjane?

[timmyjane]

yes for a little while it did then it got to be every time. it would idle but would die as soon as it was given throttle.

this was also a brand new bike.

[pedez2000]

check coil and valves.real common

[eriswerks]

I did a valve adjustment yesterday. Sure enough, the factory clearance was near zero. I set it to .005, closed everything back up and gave it a try... it started right up. I'm tentatively calling this thing fixed! I planned on swapping out the CDI to remove the RPM limit anyway, and the CDI I'm looking at comes with a new ignition coil, so I'll be doing that soon also for good measure.

[eriswerks]

Well, the scooter is offically un-fixed. After working fine for a week and a half, it's back to having the exact same problem.

Tonight I tried spraying some starter fluid into the air intake and then starting it... It ran like a bastard until the fluid was used up, and then sputtered and stalled. That sounds like a fuel delivery problem, right? Having already replaced the vacuum petcock and fuel filter, checked for kinked lines, and cleaned the carb, I'm not sure what to do next in that department. What have I overlooked?

[scootdoggydog]

maybe a gas tank vent problem try running it with the gas cap loose

[uniquescooter]

If the scoot has a vacuum operated fuel pump which it looks like it does. You will see 2 vacuum Y's going to no where. If it has vacuum Y's remove and discard them. Run 2 separate vacuum lines 1 straight to the fuel pump and one straight to the evaporative canister. Adjust the carb by backing out on the fuel mixture screw because now you will be getting adequate fuel pressure. Then ride like the wind.

[jake318]

2nd son scooter a MC-54-150 roketa new , same problem , ditching C.A.R.B carburator eventually a problem will occur and also adding mr gasket 42 inline fuel pump 40$ Jake

[jake318]

PS also you can (if you have an open space) get an inline petcock at advanced auto 3.99. Gives more fuel and is constant flow . Vaccum pumps pull less as revs increase , when you need more fuel to begin with . Jake

[jake318]

Regular cv carburator did the trick(2nd new C.A.R.B carburator I had to throw away) If you have a plug on your overflow curse a treehugger and order a cheap cv carb ...Jake

[eriswerks]

Thanks for the replies. I do have a vacuum petcock right now... I've replaced the original, but the replacement one is pretty much the same thing.

Is the mr gasket inline fuel pump an electric pump? Would you use that in combination with the inline petcock, which I'd assume is a manual switch and not vacuum-operated?

I'd like to get it working with the stock carb if I can. I see scooters driving around every day with this carb, so it can't be complete crap. Maybe I'm just stubborn, but I feel like it should have worked fine out of the box, and it shouldn't need to be souped up just to get basic functionality out of it.

I'll finally get to work on it again this weekend, so my plan is to change out the fuel line, try bypassing the petcock entirely to see if it changes anything (should I expect anything bad to happen?), and look into the gas tank vent.

[harrywr2]

Nov 28, 2008 11:12:38 GMT -5 eriswerks said:

Thanks for the replies. I do have a vacuum petcock right now... I've replaced the original, but the replacement one is pretty much the same thing.

Is the mr gasket inline fuel pump an electric pump? Would you use that in combination with the inline petcock, which I'd assume is a manual switch and not vacuum-operated?

I'd like to get it working with the stock carb if I can. I see scooters driving around every day with this carb, so it can't be complete crap. Maybe I'm just stubborn, but I feel like it should have worked fine out of the box, and it shouldn't need to be souped up just to get basic functionality out of it.

I'll finally get to work on it again this weekend, so my plan is to change out the fuel line, try bypassing the petcock entirely to see if it changes anything (should I expect anything bad to happen?), and look into the gas tank vent.

If your tank is the under your seat you have no need for a fuel pump. Bypassing the petcock altogether is fine for a test. When you replace the fuel lines you should replace the 'T's as well. They've been known to crack/leak.

On a 150cc bike, if your vacuum lines are nice and tight then there shouldn't be a lot of need for an electric pump even if your fuel tank is under the floor board.

Other things to look for are big gobs of paint on your fuel tank vent and fuel tank outlet.

[eriswerks]

My tank is right under the seat, higher than the carb. It sounds like the right thing to replace the vacuum petcock with, if it turns out to be necessary, is a manual fuel cutoff.. right? I guess I will pick up some T connectors too while I'm at it.

[harrywr2]

Nov 28, 2008 14:03:06 GMT -5 eriswerks said:

My tank is right under the seat, higher than the carb. It sounds like the right thing to replace the vacuum petcock with, if it turns out to be necessary, is a manual fuel cutoff.. right? I guess I will pick up some T connectors too while I'm at it.

Manual Petcock is correct. Ace has 1/4" brass Tees. 3/16" SAE J30/R7 automotive fuel/vacuum hose(About $1 a foot at most autoparts) will fit the 1/4" Tees with a little gasoline to lube the hose. Plastic tends to become brittle when cold. The automotive grade hose and brass tee's are good for at least 10 years.

I tried 1/4" hose for fuel lines but they didn't fit quite snug and ended up running all 3/16".

Standard OEM hose is 5mm which works out to be .2 inches.

[eriswerks]

Well, I think I've got it now. I replaced the fuel line with some much thicker, nicer-looking 3/16" line from the auto parts store. I shortened the run length a little and made sure everything was clearly downhill for the whole length.

I left the vacuum petcock in for now, but I chopped almost a foot of excess vacuum tube out of the line that feeds it. I changed the T around so that the petcock is in the straight through position, rather than the right angle... I can't decide if that ought to make a difference or if that's wishful thinking. I also moved the fuel filter above the petcock, which doesn't seem to hurt anything.

The scooter started right up and seems to be going strong. I took it for a ten mile ride with two pit stops where I turned it off and back on with my fingers crossed, and it was perfect!

By the way, I noticed that I'm going 55mph with my back to the wind and 48mph into the wind. Can I really be that un-aerodynamic?

[harrywr2]

Your only problem with the fuel filter above the petcock will be changing the fuel filter.

As far as Aerodynamics...a 50cc will get you up to 30 or so The rule of thumb in aerodymanics is double the speed, square the power. If a 3 HP 50cc will go 30 then it will take a 9HP engine to go 60.