Tao Tao 150 wont idle/just dies By lawless211 (Read 7,426 times)

[90GTVert]

Do your best to create a steady downhill routing of the fuel hose and you may improve flow. Personally, I ditch the vacuum petcocks. I hate them. They're way too prone to failure. I just replaced one on my 150 a few days ago because it was very slow filling the lines. If you measure the threads on your tank/petcock, sometimes you can find a manual shutoff that threads on. Mine was M16x1.5, but there are 14mm and probably others. I found it on eBay for $6 shipped. You can get them without the reserve function too. I don't really have a use for reserve, but it was $3-4 more for the plain ON/OFF version.



I don't know that the replacement is necessary here, because it runs above idle where it should demand more fuel. You can try a couple of simple things to see if fuel is playing a role in your starting difficulties. Cover the inlet of the airbox with your hand or partially cover it. That will restrict airflow and enrich the mixture. If it fires up and idles well doing that, you can be pretty sure you need to keep investigating fuel delivery. You can also disconnect the airbox and see if it starts that way. That leans it out and if it does better that way, you're getting too much fuel. You can look at the spark plug after you try to start it as well to see if it's wet or dry. If it's soaked you know you have fuel and possibly too much. If it's totally dry, you aren't getting fuel.

I think I'm seeing an aftermarket CDI, a blue one, mounted to the scoot. I can't really tell. If so, try putting the stock CDI on. I don't really think that is your problem. The reason I'm suggesting it is that it may help until you get it sorted out. Many aftermarket CDIs have a flat timing "curve", so they will advance the timing even at starting and idle speeds. This can make even a scooter in good working order harder to start.

[JR]

Here is another solution for replacing the petcock and I must stress blowing out all the drillings, with this you can get a simple inline gas cut off valve at any lawn mower shop:

thescooterprofessor.proboards.com/thread/4238/install-manual-fuel-cutoff-valve

Also remember you will need to plug off the vacuum line to the petcock.

JR

[lawless211]

JR

Fixed filter, double checked valves, re-set mixture screw, but there definitely seems to be a problem with the petcock, even though I got a solid flow when I tested it, but today it doesn't do anything when I pull syrenge on the air line.

If I do like in that last video and plug off the petcock, do I also just plug off the air lines coming from manifold and carb?

[JR]

Jan 17, 2016 13:43:01 GMT -6 lawless211 said:

JR

Fixed filter, double checked valves, re-set mixture screw, but there definitely seems to be a problem with the petcock, even though I got a solid flow when I tested it, but today it doesn't do anything when I pull syrenge on the air line.

If I do like in that last video and plug off the petcock, do I also just plug off the air lines coming from manifold and carb?

Like most scooters the line coming off the intake manifold splits with a Tee. Trace the line from the petcock and if it hooks to the Tee then remove it and then hook up a single line without the Tee to the other place the vacuum line goes to which most of the time is the carb. Now do also remember to plug the vacuum line input on the bottom of the fuel petcock like in the video. To test to see if the scooter will now run properly you can run the line direct from the petcock to the carb. You can install the manual fuel cutoff later.

also you do have the option of buying a new vacuum petcock if you want to.

JR

[lawless211]

JR

So jut hook up the line from carb --> intake manifold without the tee to the petcock? I guess that seems like the only option if the petcock is plugged off, but seems strange.

[JR]

Yes the carb has a need for vacuum also and will need to be hooked up. With the petcock being drilled out there will be no need for vacuum thus eliminating the line to it.

JR

[lawless211]

JR cyborg

You guys are giving me great feedback and I am very thankful and I am glad I am trying to fix this myself, but I am about to lose it.

I set up the petcock to run without the vacuum, drilled it out, cleaned it out, set up an in-line cut-off valve, ran hose from intake to carb, plugged off air line on petcock. The gas line gradually drops down to carb so gas should run down. I had to give it some assistance to get it started. I definitely got her running the best since we started this, but wasn't great by any means. There were still air bubbles making their way up the gas line, maybe because the first inch of gas line is tilted up a little bit, but i would think the tank pressure would get it past it no problem? It's the angle of the petcock that makes it tilt slightly.

I saw a tiny bit of moisture in the line from manifold to carb. A very small amount, but still some.

She ran without me toying throttle for a little while, but idle was going up and down.

I shut her off and then there was a little smoke coming out of exhaust. 

[JR]

lawless211 remove the gas cap and see if the fuel flows better.

JR

[90GTVert]

It's normal to see an air pocket in high spots along the fuel path. If you're suspicious of fuel flow you can remove the line from the carb or outlet side of the shutoff valve and let it drain into a container. You can even loosen the bowl drain and test right from the bowl if you'd like. I've done mine before by watching a timer so it flows for exactly a minute, then measuring the fuel when I was really suspicious of the fuel getting to my carb. Just did this last week actually. With 3/16" fuel lines I was getting 160ml per minute with straight down fuel hose routing. With it routed the best I could seem to get it (because I have a similar issue where the location of the petcock outlet makes it go mildly uphill at first) I got 140ml/min. Checked with the fuel cap off, same. I checked from the drain as well and got very close to the 140ml/min. Not really necessary, but if you can't tell that it's enough by watching it or find that sort of thing interesting it's an option.

Surging idle could be a sign of a vacuum leak. You may want to double check that you haven't created any while rearranging your vacuum setup. A lean idle would also be likely to cause RPM to hang at least slightly if you rev a little then let off. If you indeed had a fuel supply issue that is cured now, readjustment of the mixture screw may be required. Fuel vapor could be getting into the vacuum hose to create moisture. It's not old fuel is it? Air filter clean? Any backstory we need to know, like the scooter sat for a long time or has never ran well since you owned it etc...?

[lawless211]

Jan 18, 2016 5:35:14 GMT -6 JR said:

lawless211 remove the gas cap and see if the fuel flows better.

JR

JR

No, not anything noticeable.

[lawless211]

Jan 18, 2016 8:22:38 GMT -6 90GTVert said:

It's normal to see an air pocket in high spots along the fuel path. If you're suspicious of fuel flow you can remove the line from the carb or outlet side of the shutoff valve and let it drain into a container. You can even loosen the bowl drain and test right from the bowl if you'd like. I've done mine before by watching a timer so it flows for exactly a minute, then measuring the fuel when I was really suspicious of the fuel getting to my carb. Just did this last week actually. With 3/16" fuel lines I was getting 160ml per minute with straight down fuel hose routing. With it routed the best I could seem to get it (because I have a similar issue where the location of the petcock outlet makes it go mildly uphill at first) I got 140ml/min. Checked with the fuel cap off, same. I checked from the drain as well and got very close to the 140ml/min. Not really necessary, but if you can't tell that it's enough by watching it or find that sort of thing interesting it's an option.

Surging idle could be a sign of a vacuum leak. You may want to double check that you haven't created any while rearranging your vacuum setup. A lean idle would also be likely to cause RPM to hang at least slightly if you rev a little then let off. If you indeed had a fuel supply issue that is cured now, readjustment of the mixture screw may be required. Fuel vapor could be getting into the vacuum hose to create moisture. It's not old fuel is it? Air filter clean? Any backstory we need to know, like the scooter sat for a long time or has never ran well since you owned it etc...?

90GTVert

The longest it has sat is the past 2 weeks that I can't get it to work, but I have been starting it here and there when working on it. Yes, i replaced it with new fuel. It ran great for awhile, but have only had it since July when I got it new.

There is a small crack in intake manifold which I know is bad and could cause these problems, but I have been plugging it up. I might as well wait for my new one which should be here soon. I believe it happened when putting the new carb on. I feel like it shouldn't be that troublesome if I am plugging it up. Tonight when I finally got it to start, I noticed it wasn't plugged well anymore so I shut the scooter off. I removed the plugging and white smoke was coming out of it. Would that smoke be in there anyway, or is that another problem?

Anybody know a scooter tech in DFW? Otherwise, I will continue to rely on you guys. 

[JR]

lawless211 The cracked manifold is your problem and even though you are plugging the crack it's not sealing well, when the new one comes in then after installing it let us know what's going on.

JR

[90GTVert]

I'm guessing what you saw were fuel vapors. Hopefully anyway. True smoke wouldn't be good to be coming out of the intake. I'm with JR on this and say your best bet is to wait on that new intake. One of the first rules of troubleshooting IMO should be to take care of known problems.

[lawless211]

JR

The new intake manifold came in, so I took off the old one with the crack in the rubber, looked inside, and saw that it so much worse than it appeared on the outside. The metal had a crack a bit longer than an inch. Everything is running great now. I wish I would have noticed the crack earlier, but I am glad I replaced the parts that I did and updated the fuel petcock style. The only question I have for that is.... There wasn't a convenient place to put the in-line valve where I can get to it easily, but will just have to pull the seat out. Should I close it off everytime I park, or at the end of the day, or just if its going to sit for a couple days?

Other than that, I am very thankful for all the support. This is a fantastic resource for all scooterers...is that a word?

Thank you guys for what you do.

[JR]

It's better to shut it off but pain to pull the seat, IMO I would order a new vacuum petcock and see if that works well now.

JR