At wit's end- Won't start!

[animusdraconis]

I bought this 49 CC TaoTao about a month ago. Daily use for doordash, downtown Denver. Been driving it about 80 miles a day, been chugging along with no issue.



Uuuntil yesterday. I filled up with 91 and got about another 2 miles upon which on a downhill stretch the engine started chugging and was kinda sputtering, once on flat ground again, it would not climb above 15 mph. I turned it off, and it hasn't started since.

Now, 2 days ago I took a spill cuz it started raining really hard out of nowhere. I think that might've been part of the problem but I am not sure. There are no broken wires though, and I was doing 5 mph coming into my apartment parking lot on a turn so not sure what it could've done.

So far, I have replaced the spark plug, checked the vacuum line and fuel line - both fine, although I had a bit of a leak in my fuel line, which I did repair. The fuel valve functuons fine, spits a nice stream of gas when the fuel line is disengaged.

I've checked that there is indeed a spark. I have pulled the spark and let it air for 3 hours in 92 F, sunny weather, I drained the carburetor of gas, I have tried manually choking I have tried starting and throttling. I pulled the case and checked the starter belt - it is a little frayed, but otherwise fine.

I have tried partial starts by getting a run and hopping on.

I cannot think of anything else beyond a seized engine, but if I start without a plug, it free spins just fine.

Somebody save me lol.

[tortoise2]

No mention of checking valve clearance?

[animusdraconis]

Jun 28, 2019 21:03:04 GMT -5 tortoise2 said:

No mention of checking valve clearance?

This, I was not aware of! Will try in the morning. Is this a problem that pops out of nowhere, or could a fall cause it??

[GrumpyUnk]

You cannot push start a Taotao, or any other China 139QMB scooter. The rear wheel, via the gearbox, will spin the 'clutch bell' very fast when you try to push start.
A frayed belt is a worn belt, and likely in need of replacement.

Take a look at where the belt is currently riding in the front(variator) and rear(clutch) pulleys. If the rear pulley is down near the center, and the front near the outer edge, you likely have a broken clutch(actually the part that moves the pulley sidewall) that has jammed up with the ratio being in 'high gear'.
You should be able to grab hold of the clutch pulley vee and squeeze it towards yourself, allowing the belt to get loose enough for removal. The vee should move, not easily, but not jammed and immobile.
The front pulley(variator) should naturally have the belt down in the groove as far as it can go. The clutch pulley should have pulled it there as you slowed down back when. If the variator pulley is not down in the bottom of the vee, then something is wrong. The sliders want to squeeze the vee together, making the 'pulley' effectively become larger. If it is already squeezed... something is broke.
Over time the gizzards that allow the clutch pulley to get wide and narrow become worn, and can get jammed. If you go real fast(not that you did) it seems that is the time they like to break. I dunno why. If it is broken, the belt will be down in the clutch pulley vee rather deep.
If you crank the engine using the kick starter, by HAND, can you feel the piston go round- intake, compress, fire, exhaust. You should feel more resistance for 1/2 of a revolution during compression. If not, pull the plug, and put a thumb over the spark plug hole while using the kick starter to rotate the crankshaft. There should be enough compression to move your/someones thumb off the plug hole.
tom

[ncsteve]

My first thought is a tank of bad gas. If the sputtering started right after filling up,I would drain the tank and carb and try some fresh gas.

[oldunclestevo]

Jun 28, 2019 21:37:29 GMT -5 animusdraconis said:

Jun 28, 2019 21:03:04 GMT -5 tortoise2 said:

No mention of checking valve clearance?

This, I was not aware of! Will try in the morning. Is this a problem that pops out of nowhere, or could a fall cause it??

Ive had valve adjustments creep up on me in the past. It was usually a little more gradual, but IMO it could come out of nowhere seemingly. Regardless checking the valve clearance is a good idea

[crawford]

compression test will tell a lot