Finally borrowed a battery and working on 50 cc motor scooter.
It doesn't start right away -- kick starting would never work because of that -- but after maybe the 4th try at 10 to 15 seconds each, it starts, but then starts to slow down 10 seconds later. Sometimes stalls right then. Turning the accelerator sometimes makes it speed back up but then 10 seconds later it slows and stalls.
What's the problem?
A little bit of old gas but a gallon of new gas (which is about half a tank.)
I'm not sure if ether helps or not. It certainly doesn't start right away when I use it.
I think I remember reading that there was a fuel filter, but I haven't seen it.
For some reason I started another thread, where I point out that it starts every 10 minutes, so I don't think it's a gunked up carb, but maybe it takes 10 minutes for 30 seconds of fuel to seep through the filter. It might run on ether too, but of course that either dissipates or gets burned up in about 15 seconds also.
If I had someone to spray while it was running, I coudl see if it ran longer. I know it's bad for the engine, but another minute total won't hurt. I have to hold the brake so I can't spray too. If the engine runs fast enough, the, get this, automatic transmission puts it in drive so if I don't hold the brake, who knows where it would go?
Get a gas can, disconnect the gas line at the carb, and let a quart run into the can. Does the gas flow out or is it running slow? Replace the fuel filter if it runs slow. Reattach the gas line. Ok, you've eliminated the old gas and the gas line/filter. Try and start it now. If the symptoms have not changed I'd suspect crud in the carb. What's the story behind this scooter?
Pinched line? If you take the gas cap off will it run longer? If there's no way for the tank to breathe that could cut off flow.
What kind of petcock does it have? I've got a manual on one bike and if I forget to turn it on I can get about 100 yards before the float bowl runs dry. Vacuum actuated petcocks can act up too or the vacuum line could be leaking. Is there a prime position?
I tried to disconnect it there, and I got the thin spring wire "hose clamp" to move down the hose but couldnt' get the hose off.
If I took off the electric choke (two phillips screws) I might have more access, not sure. All the pictures/diagrams are from the right side, and this is on the left. (182 page manual, 22 megs)
No chance of getting even a little can in there. I was just going to spill some.
Then I tried just below the fuel-pump-like-thing (well not really except it's in the middle of the fuel line, where a pump would be. I assume gravity is the major pump). They call it the control valve and it has a vacuum line on it. The line goes to the base of the carburetor, so I guess when there is vacuum there it either opens or closes the gasoline path, maybe. This might be broken.
Got the gas hose clip moved and there was room to put in a screw driver, but didn't have one.
Then I tried just above the control valve, moved the hose clip, and I did have a tool to get in there, but it didnt' budge yet. Hoses get stuck to the metal. Then I went on to something else.
The sell a filter for this engine, $5, but I don't think I saw it in there. Maybe it was just under the tank*** and if that's the case, any of those three places to disconnect will be good enough for testing.
*** Tomorrow I'll use a mirror. If it's there, it seems more likely than the control valve. It's not mentioned in the manual. (using Adobe reader, for some reason Find doesn't work, at least with these manuals. It says it's searching 180 pages, but never finds words I know are there. Well I just changed to a word showing on the page I'm on, and it immediately said it wasn't found, it didn't even scan all the pages. Also can't highlight or copy from the long, repair manual **** but I can from the owners manual, though find doesn't work right there either. If I search for one word, then another, it says it can't find the second, unless I scroll in between. No Adobe Reader updates available.
****Under file/properties it says there is "password security" and I don't know the password, or even where to enter it.
Found it in the woods near my house. Called the police but he looked at it, saw all the damage I guess, and said he didn't want it. No reports of a missing scooter, he said. A neighbor said it had been there for 2 days. Plent of time to be reported. I told him to come back if he got a report. Well, what she said is that she'd seen two teenagers pushing it down the street in front of our houses. Why they didn't just leave it where they were, I can't guess. Maybe it's de rigeur to dump things in the woods. Although in 30 years there have only been this and 2 bicycles and one shopping cart.
I'm not sure it has any. It has something called a control valve, with gas in and out and a vacuum line from the base of the carburetor. ??
Is that what the control valve is?
I doubt it. The hoses all look in good condition. But there's a diaphragm inside, I presume. Maybe something's wrong there.
I have to see if gas is coming through the filter -- there must be filter because it's in the maintenance schedule, even if there's no other mention in the repair or owners manual.
And I have to see if gas is coming through the control valve. Tomorrow.
Sounds like a vacuum operated petcock. A potential problem with gravity feed fuel systems is a leaking float needle in the carburetor itself or a stuck float. The float bowl fills and the gasoline starts to run out of the carb. Worst case, it fills the cylinder and/or crankcase with gasoline.
Traditionally there was just a manually operated valve on the bottom of the tank, with on, off, and maybe reserve. Reserve just uncovered a lower hole in the tube inside the tank. When you started sputtering in the normal position you switched to reserve and might get a half gallon or so additional fuel. Of course, if you reached down and found you were already on reserve you started walking.
Like everything else, that was too complicated for people, so they went to a vacuum operated valve, with a hose going to the carb for the vacuum. Those generally still have a three way lever, on, off, and prime. Prime manually opens the valve in case there's a problem with the vacuum operator.
With my Sportster, the filter is in the tank itself. You remove the fitting and the whole assembly comes out. Of course, being in the bottom of the tank means you wait until the tank is less than half full, remove it, and prop it up on its side. Or, if you're not too mechanically savvy you remove the fitting in place and pour a couple of gallons of unleaded down your leg. Adds character to your jeans like in the old ZZ Top song.
Every time I take the nozzle out of my oil furnace, I pour the oil that's in the tube connected to the nozzle onto the floor, or my shoe. Except the last time. After 15 or 20 times, I finally remembered not to do that.
So I have 14 times to go before i get the scooter gas tank right.
I'm glad you posted. If that's where it is, I wouuldn't have found it.
What kind of scooter is it? There should be some service information online. Unless it's a Chung King Lightning Bolt or one of those other cheap Chinese scoots. They are creative. One of them was called something like Fubar 800. The displacement was around 50cc but the crankcase held 800cc's of oil.
That's right. Low actually. 50cc's and 1 liter of oil. The piston is only 1.33 inches and the stroke is 1.63 inches.
(and I see it has the factory-specified plug, and I measure the gap and it was just right.)
It's a Tautau 50cc ATM50-A1. People won't find more documentation on-line than I have, I was pretty diligent and I found plenty. I have dl'd the owner's manual, 40 pages, and the generic service manual, 180 pages (including the wiring schematic which almost? exactly matches the scooter), and some other manuals for similar scooters, GY6 and Panterra, but none of them show the gas filter. They list it in the mainenance schedule, though, so I figured there was one.
**Some other models are 49.5cc. I think there are some laws that apply to bikes 50cc and above, so they made those less.
I also have the GY6 troubleshooting guide, which I had forgotten to look at (I actually avoided looking at it until today, but today I'm willing to look.) The closest it has is for Low Engine RPM, for which it lists: Air filter blocked Fuel choke Fuel tank cap air bleeder blocked -- so it really could have been the cap after all, but it's not. Exhaust pipe blocked Auto choke bad Carburetor diaphragm Automatic oil cup bad.
Like most troubleshooting charts it doesn't list everything that could be the problem.
Plus I joined a scooter web list, but I hate web lists, and it's only worth asking there about things that are too obscure for the people here to know. Like where can you get body parts for this model.
.... It has an overhead cam engine! But a maximum speed of 30, iirc.
Have you looked at YouTube, lots of repair videos? Are you using high octane fuel? This scooter does not have a fuel pump. It does have a fuel regulator. What you've been describing may be a vacuum leak somewhere.
First thing to do is eliminate the vacuum operated fuel petcock. Take the block out of the fuel line and join the lines with an inline splice or a manyal huel shutoff. Plug the vac line. See if it runs then.
From your description - a 4 stroke 50cc scooter, that is the most likely problem - followed by a junked up carb.
Removong thr float bowl and checking for "greenies" and other crap would tell you if that is the problem - but because it actually runs for a short time, I'd put that well down the probability scale from the fuel shutoff block.
Sure, why not. OHC implies it's a four stroke. A lot of the 50cc class are two stroke since you can get about twice the power even if you are trailing a blue cloud of smoke. The 49.9cc may also work for the two stroke bans.
I did most of this today. Test 1: I took the hose off the fuel filter and gas poured out.
I put that back and took the hose off the exit of the vacuum petcock. A little bit of gas dribbled out, though later it didnt' seem to always dribble when closed.
But I disconnected the vacuum line and sucked on it and gas pretty much poured out of the petcock. Probably not as much as Test 1. That is, the stream narrowed a bit right after coming out of the petcock. Hmmm. that didn't worry me at the time, but tomorrow i'll do what you say, an inline splice.
Still, later I found some 1/4" OD hose and put a piece where the vac line was and plugged it with a nail. I also put a 2" piece on the port that had had the 2" piece that went nowhere. And I tied the brake handle closed so I didn't have to keep holding it. And I put a long hose on the petcock. Then, when it was started, I sucked on the hose and that was enough to open it when the engine wasn't running, but still it started to stall in just about the same length of time, and loped slowly for another 10 seconds. Several times.
Later I was finally able to get the fuel hose off the carburetor and when I sucked on the petcock, the fuel came out pretty fast. **
A video had used red and blue "clear" tubing, so I used clear tubing, and while I was sucking, I could still see my saliva going down the tube pretty fast. I didn't think I was letting any out, so that was strange. But it never made it closer than a foot from the petcock.
I also was able to spray starter fluid while it was running and that didnt' seem to make it run longer. Once it ran faster, for a short while but even that didnt' usually happen. Is it possible to spray in too much ether. It never was in a car but those engines were probably
200x as big.
When it's running, it sounds pretty good.
**OTOH, even after diluting the old gas with a new gallon, now that I see the gas coming out of the disconnected hose is creamy brown, not transparent brown like I remember. I also got some on my hands and it doesn't smell like I remember gasoline smelling.
I should drain all this crappy gas, shouldn't I, but if it runs with it for 15 seconds, that couldn't be the reason it stalls, could it?
I googled "old gas makes engine stall" and got several hits and I'm reading them now (well, not right now.)
Here's one:
formatting link
Phase Separation in Ethanol Blended Gasoline Happens when there's too much water in the gasoline.
It turns into layers. Maybe when I wait 10 minutes, the gasoline rises to the top of the carburetor bowl.
Now that I have the extra hose, I can find a coupling and drain the gas into something.
BTW, I no longer think thieves or vandals removed the seat. The owner took the seat off to get to the engine to try to fix this thing. Maybe he even did the other damage too when he fell. Why it was rolled/pushed to the woods is still a mystery.
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